text:
*Chairperson, Clinical Task Force. Chairperson, Imaging Task Force. See the appendix for a complete listing of the members of the Task Forces and consultants and advisors.
nitions of diagnoses should not dene or imply need for specic treatment. The task forces worked from a model that could be expanded from a primary purpose of providing understanding of reports of imaging studies. The result would provide a simple and relatively imprecise classication of diagnostic terms, based on pathology, which could be expanded, without contradiction, into more precise subclassications. When reporting pathology, degrees of uncertainty would be labeled as such rather than compromising on the denitions of the terms. All terms used in the classications and subclassications were to be dened, and those denitions would be adhered to throughout the model. For practical purpose, some existing English terms were given meanings different from those found in some contemporary dictionaries. The task forces would provide a list and classication of recommended terms, but, recognizing the nature of language practices, would discuss, and include in a glossary, commonly used and misused nonrecommended terms and nonstandard denitions. Although the principles and most of the denitions of this document could be easily extrapolated to the cervical and dorsal spine, the focus is on the lumbar spine. While clarication of terms related to posterior elements and disorders related to dimensions of the spinal canal are also needed, this work is limited to discussion of the disc. Although it is not always possible to fully discuss the denition of anatomic and pathologic terms without some reference to symptoms and etiology, the denitions, themselves, stand the test of independence from etiology, symptoms, or treatment. Because of the focus on anatomy and pathology, this work does not dene certain clinical syndromes that may be related to lumbar disc pathology. Guided by those principles, this document provides a universally acceptable nomenclature that is workable for all forms of observation, that addresses contour, content, integrity, organization, and spatial relationships of the lumbar disc; and that serves a system of classication and reporting built on that nomenclature. Recommendations These recommendations present diagnostic categories and subcategories, intended for classication and the reporting of imaging studies. The terminology used throughout these recommended categories and subcategories remains consistent with detailed explanations given in the Discussion section and with the preferred denitions presented in the Glossary. The diagnostic categories are based on pathology. Each lumbar disc can be classied in terms of one, and occasionally more than one, of the following diagnostic categories: Normal; Congenital/Developmental Variation; Degenerative/Traumatic; Infectious/Inammatory; Neoplastic; and/or Morphologic Variant of Uncertain Signicance (Table 1). Each diagnostic category can be subcategorized to various degrees of specicity accord-
ing to the information available and purpose to be served. The data available for categorization may lead the reporter to characterize the interpretation as possible, probable, or denite.
Normal Normal denes young discs that are morphologically normal, without consideration of the clinical context and not inclusive of degenerative, developmental, or adaptive changes that could, in some contexts (e.g., normal aging, scoliosis, spondylolisthesis) be considered clinically normal. However, the bilocular appearance of the adult nucleus resulting from the development of a central horizontal band of brous tissue is considered a sign of normal maturation. Congenital/Developmental Variation The Congenital/Developmental Variation category includes discs that are congenitally abnormal or that have undergone changes in their morphology as an adaptation to abnormal growth of the spine such as from scoliosis or spondylolisthesis. Degenerative/Traumatic Degenerative and/or Traumatic changes in the disc are included in a broad category that includes subcategories of Anular Tear; Herniation; and Degeneration. Characterization of this group of discs as Degenerative/ Traumatic does not imply that trauma is necessarily a factor or that degenerative changes are necessarily pathologic as opposed to the normal aging process. Anular tears, also properly called anular ssures, are separations between anular bers, avulsion of bers from their vertebral body insertions, or breaks through bers that extend radially, transversely, or concentrically, involving one or many layers of the anular lamellae. The terms tear or ssure describe the spectrum of such lesions and do not imply that the lesion is consequent to trauma (Figure 1). Degeneration may include any or all of real or apparent desiccation, brosis, narrowing of the disc space, diffuse bulging of the anulus beyond the disc space, extensive ssuring (i.e., numerous anular tears), and muci-
Figure 1. Schematic sagittal anatomic sections showing the differentiating features of an anular tear (radial tear in this case) and a disc herniation. The term tear is used to refer to a localized radial, concentric, or horizontal disruption of the anulus without associated displacement of disc material beyond the limits of the intervertebral disc space. Nuclear material is shown in black, and the anulus (internal and external) corresponds to the white portion of the intervertebral space. The same convention is used in Figures 2, 11, 12, and 13. (Adapted with permission from Milette PC. The proper terminology for reporting lumbar intervertebral disk disorders. AJNR Am J Neuroradiol 1997; 18: 1859 1866.)
Figure 3. The term herniated disc, as dened in this work, refers to localized displacement of nucleus, cartilage, fragmented apophyseal bone, or fragmented anular tissue beyond the intervertebral disc space (disc space, interspace). The interspace is dened, craniad and caudad, by the vertebral body endplates. Two intravertebral herniations, one with an upward orientation and the other with a downward orientation with respect to the disc space, are illustrated schematically.
nous degeneration of the anulus, defects and sclerosis of the endplates, and osteophytes at the vertebral apophyses. A disc demonstrating one or more of these degenerative changes can be further qualied into two subcategories: spondylosis deformans, possibly representing changes in the disc associated with a normal aging process; or intervertebral osteochondrosis, possibly the consequences of a more clearly pathologic process (Figure 2). Herniation is dened as a localized displacement of disc material beyond the limits of the intervertebral disc space (Figure 1). The disc material may be nucleus, cartilage, fragmented apophyseal bone, anular tissue, or any combination thereof. The disc space is dened, craniad and caudad, by the vertebral body endplates (Figure 3) and, peripherally, by the outer edges of the vertebral ring apophyses, exclusive of osteophytic formations (Figure
4). The term localized contrasts to generalized, the latter being arbitrarily dened as greater than 50% (180 degrees) of the periphery of the disc (Figure 5). Localized displacement in the axial (horizontal) plane can be focal, signifying less than 25% of the disc circumference (Figure 6), or broad-based, meaning between 25 and 50% of the disc circumference (Figure 7). Presence of disc tissue circumferentially (50 100%) beyond the edges of the ring apophyses may be called bulging and is not considered a form of herniation (Figure 8), nor are diffuse adaptive alterations of disc
Figure 2. Schematic sagittal anatomic sections showing the differentiating characteristics of the normal disc, spondylosis deformans, and intervertebral osteochondrosis. The distinction between these three entities is usually possible on all imaging modalities, including conventional radiographs. (Adapted with permission.25)
Figure 4. The interspace is dened, peripherally, by the edges of the vertebral ring apophyses, exclusive of osteophytic formations. The line drawing schematically illustrates a localized extension of disc material beyond the intervertebral disc space, in a left posterior direction, which qualies as a disc herniation.
Figure 5. For classication purposes, the intervertebral disc is considered as a two-dimensional round or oval structure having four 90 quadrants. By convention, a herniation is a localized process involving less than 50% (180) of the disc circumference.
Figure 7. By convention, a broad-based herniation involves between 25% and 50% (90 180) of the disc circumference.
contour secondary to adjacent deformity as may be present in severe scoliosis or spondylolisthesis (Figure 9). Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material (Figure 10). Protrusion is present if the greatest distance, in any plane, between the edges of the disc material beyond the disc space is less than the distance between the edges of the base, in the same plane. The base is dened as the cross-sectional area of disc material at the outer margin of the disc space of origin, where disc material displaced beyond the disc space is continuous with disc material within the disc space. In the cranio-caudal direction, the length of the base cannot exceed, by denition, the height of the intervertebral space. Extrusion is present when, in at least one plane, any one distance
between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base, or when no continuity exists between the disc material beyond the disc space and that within the disc space (Figure 11). Extrusion may be further specied as sequestration, if the displaced disc material has lost completely any continuity with the parent disc (Figure 12). The term migration may be used to signify displacement of disc material away from the site of extrusion, regardless of whether sequestrated or not (Figure 13). Because posteriorly displaced disc material is often constrained by the posterior longitudinal ligament, images may portray a disc displacement as a protrusion on axial sections
Figure 6. By convention, a focal herniation involves less than 25% (90) of the disc circumference.
Figure 8. Symmetrical presence (or apparent presence) of disc tissue circumferentially (50 100%) beyond the edges of the ring apophyses may be described as a bulging disc or bulging appearance and is not considered a form of herniation. Furthermore, bulging is a descriptive term for the shape of the disc contour and not a diagnostic category.
Figure 9. Asymmetrical bulging of the disc margin (50 100%), such as what is found in severe scoliosis, is also not considered a form of herniation.
and an extrusion on sagittal sections, in which cases the displacement should be considered an extrusion. Herniated discs in the cranio-caudal (vertical) direction through a break in the vertebral body endplate are referred to as intravertebral herniations. Disc herniations may be further specically described as contained, if the displaced portion is covered by outer anulus, or uncontained when absent any such covering. Displaced disc tissues may also be described by location, volume, and content, as discussed later in this document. Table 2 lists the proposed categories for description and classication of disc herniations.Inflammation/Infection The category of Inammation/ Infection includes infection, infection-like inammatory discitis, and inammatory response to spondyloarthropathy. It also includes inammatory spondylitis of subchondral endplate and bone marrow manifested as Modic Type 1 magnetic resonance imaging (MRI) changes and usually associated with pathologic changes in the disc. To simplify the classication scheme, the
Figure 11. When a relatively large amount of disc material is displaced, distinction between protrusion (A) and extrusion (B or C) will generally only be possible on sagittal magnetic resonance (MR) sections or sagittal computed tomography (CT) reconstructions. C, Although the shape of the displaced material is similar to that of a protrusion, the greatest cranio-caudal diameter of the fragment is greater than the cranio-caudal diameter of its base at the level of the parent disc, and the lesion therefore qualies as an extrusion. In any situation, the distance between the edges of the base, which serves as reference for the denition of protrusion and extrusion, may differ from the distance between the edges of the aperture of the anulus, which cannot be assessed on CT images and is seldom appreciated on MR images. In the craniocaudal direction, the length of the base cannot exceed, by denition, the height of the intervertebral space. (Reprinted with permission from Milette PC. Classication, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:12671292.)
category is inclusive of disparate conditions; therefore, when data permit, the diagnosis should be subcategorized for appropriate specicity.
Neoplasia Primary or metastatic morphologic changes of disc tissues caused by neoplasia are categorized as Neoplasia, with subcategorization for appropriate specicity.
Figure 10. Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material (see denitions in text).
Figure 12. Schematic representation of various types of posterior central herniations. A, Small subligamentous herniation (or protrusion) without signicant disc material migration. B, Subligamentous herniation with downward migration of disc material under the posterior longitudinal ligament (PLL). C, Subligamentous herniation with downward migration of disc material and sequestered fragment (arrow). (Reprinted with permission from Milette PC. Classication, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:12671292.)
ture that facilitates description of surgical or endoscopic ndings as well as images; and also, with the caveat that it addresses only the morphology of the disc, it facilitates communication for patients, families, employers, insurers, and legal and social authorities, and permits accumulation of more reliable data for research.
Figure 13. Relationship of typical posterior disc herniations with the posterior longitudinal ligament. A, Midline sagittal section: Unless very large, a posterior midline herniation usually remains entrapped underneath the deep layer of the PLL and sometimes a few intact outer anulus bers joining with the PLL to form a capsule. The deep layer of the PLL (arrow) also attaches to the posterior aspect of the vertebral body so that no potential space is present underneath. B, Sagittal para-central section: The PLL extends laterally at the disc level (arrowhead) but, above and below the disc, an anterior epidural space (as), where disc fragments are frequently entrapped, is present between the lateral (peridural) membranes and the posterior aspect of the vertebral bodies. (Adapted with permission from Milette PC. Classication, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000;38:12671292.)
Normal Categorization of a disc as Normal means the disc is fully and normally developed and free of any changes of disease, trauma, or aging. Only the morphology, and not the clinical context, is considered. In common practice, people with a variety of harmless congenital or developmental variations of discs, minor bulging of anuli, anterior and lateral marginal vertebral body osteophytes, etc. are normal people. By this nomenclature and classication, however, such individual discs are not considered normal. Therein lies a signicant difference of this method from what many would consider common practice. Some people are clinically normal even though they have morphologically abnormal discs. Anular Tears/Fissures There is general agreement about the various forms of loss of integrity of the anulus, such as radial, transverse, and concentric separations. Some, including the 1995 NASS document,15 have recommended that such lesions be termed ssures rather than tears, primarily for fear that the word tear could be misconstrued as implying a traumatic etiology. Common practice, as documented by review of contemporary specialty journal literature12 shows preference, among authors of various disciplines, for the term tear, and frequent synonymous use in the same articles of the terms tear and ssure. In this instance, it is unwise to recommend contrary to ingrained common usage but wise to reiterate the caveat that the term anular tear does not imply traumatic etiology. In the case where a single, traumatic event is clearly the source of loss of integrity of a formally normal anulus, such as with documentation and ndings of violent distraction injury, the term rupture of the anulus is appropriate, but use of the term rupture as synonymous with commonly observed tears or ssures is contraindicated. In conclusion, therefore, anular tear and anular ssure are both acceptable terms, can be used properly as synonyms, and do not imply that a signicant traumatic event has occurred or that the etiology is known. Some tears may have clinical relevance and others may be asymptomatic and inconsequential components of the aging process. Correlation of the characteristics of the tear with responses to discography and other clinically relevant observations may enable the observer to make such distinctions, but such is beyond the scope of this morphologically based denition and classication model.
Morphologic Variant of Unknown Significance Instances in which data suggest abnormal morphology of the disc but are not complete enough to warrant a diagnostic categorization can be categorized as Morphologic Variant of Unknown Signicance.Discussion Acceptance and standardization occur most easily when recommendations are close to common practice. However, there are many contradictory views of common practice and some common practices are contradictory to our primary purpose, which is clear communication between those who interpret images and those who make clinical decisions. This document denes a nomenclature that describes discs and leaves to the clinician the description of the patient. In so doing, however, this provides a nomenclaTable 2. Description of a Disc Herniation Morphology Protrusion Extrusion Intravertebral Containment Continuity Relation with PLL complex Volume Composition Location
Disc Degeneration Because there is confusion in differentiation of changes of pathologic degenerative processes in the disc from those of normal aging,8,30,38 the classication category Degenerative/Traumatic includes all such changes, thus does not compel the observer to differentiate the pathologic from the normal consequences of aging. However, this model allows the observer with adequate data to present a more enlightening report by making such a distinction, with appropriate notation of the degree of condence. Perceptions of what constitutes the normal aging process of the spine have been greatly inuenced by postmortem anatomic studies involving a limited number of specimens, harvested from cadavers from different age groups, with unknown past medical histories, and the presumption of absence of lumbar symptoms.7,9,17,20,23,34 With such methods, pathologic changes are easily confused with consequences of normal aging. Resnick and Niwayama35 emphasized the differentiating features of two degenerative processes involving the intervertebral disc, which had been previously described by Schmorl and Junghanns37: spondylosis deformans, which affects essentially the anulus brosus and adjacent apophyses, and intervertebral osteochondrosis, which affects mainly the nucleus pulposus and the vertebral body endplates, but also includes extensive ssuring (numerous tears) of the anulus brosus, which may be followed by atrophy (Figure 2). Although Resnick and Niwayama stated that the cause of the two entities was unknown, other scientic studies suggest that spondylosis deformans is the consequence of normal aging, whereas intervertebral osteochondrosis, sometimes also called deteriorated disc, results from a clearly pathologic, although not necessarily symptomatic, process.32,36,37,40,41 With normal aging, brous tissue replaces nuclear mucoid matrix, but the disc height is preserved and the disc margins remain regular.22 Radial tears of the anulus are found only in a minority of postmortem examinations of individuals over 40 years of age,23 so cannot be considered a usual consequence of aging. Slight symmetric bulging of the disc may occur in the elderly remodeling associated with osteoporosis.41 On conventional radiographs and computed tomography (CT), small amounts of gas can be detected in some elderly individuals at the anular/apophyseal enthesis, probably located in small transverse anular tears, and possibly signifying early manifestations of spondylosis deformans49; however, a large amount of gas in the central disc space is always pathologic and is a feature of intervertebral osteochondrosis.35 Anterior and lateral marginal vertebral body osteophytes have been found in 100% of skeletons of individuals over 40, so are consequences of normal aging, whereas posterior osteophytes have been found in only a minority of skeletons of individuals over 80, so are not inevitable consequences of aging.32 Endplate erosions with osteosclerosis and chronic reactive bone marrow changes also appear to be pathologic. Slight to mod-
erate decrease in central disc signal intensity found on T2-weighted MRIs can be a nonpathologic age-related observation but, if the result of a normal process, should be relatively uniform among all discs studied in the individual. Intervertebral osteochondrosis, or deteriorated disc, also sometimes called chronic discopathy, shows, on microscopic examination, total structural disorganization and general replacement of normal disc tissue by brosis. Radiographically, intervertebral osteochondrosis is characterized by narrowing of the intervertebral space, irregular disc contour often associated with bulging, multidirectional osteophytes often involving the central spinal canal and foramina, endplate erosions with reactive osteosclerosis, and chronic vertebral body bone marrow changes. On T2-weighted images, the central disc signal intensity is usually markedly decreased, and at distinct variance, to that seen in unaffected discs of the same individual. The distinction is made at the time of the reading and does not imply that early manifestations of a pathologic process are always distinguishable from changes of normal aging.
Herniated Disc The needs of common practice make necessary a diagnostic term that covers the various permutations of disc material displaced beyond the intervertebral disc space. Herniated disc, herniated nucleus pulposus, ruptured disc, prolapsed disc (used nonspecically), protruded disc (used nonspecically), and bulging disc (used nonspecically) have all been used in the literature in various ways to denote imprecisely dened displacement of disc material beyond the interspace. The absence of clear understanding of the meaning of these terms and lack of denition of limits that should be placed on an ideal general term have created a great deal of confusion in clinical practice and in attempts to make meaningful comparisons of research studies. For the general diagnosis of displacement of disc material, the single term that is most commonly used and creates least confusion is herniated disc. Attempts to avoid whatever confusion has been created by lack of denition of the term herniated disc have included the recommendation to substitute the term disc material beyond the interspace (DEBIT),4 but that is more awkward and runs counter to common practice. Herniated nucleus pulposus (HNP) is inaccurate because materials other than nucleus (cartilage, fragmented apophyseal bone, fragmented anulus) are common components of displaced disc material.6,47,48 Rupture casts an image of tearing apart and therefore carries more implication of traumatic etiology than herniation, which conveys an image of displacement rather than disruption. Though protrusion has been used by some authors in a nonspecic general sense to signify any displacement, the term has a more commonly used specic meaning for which it is best reserved. Prolapse, which has been used as a general term, as synonymous with the specic meaning of protrusion, or to denote inferior mi-
gration of extruded disc material, is not commonly used and is best proscribed. The term bulging disc has been used to mean many things and has caused a great deal of confusion, as discussed below; therefore, its use as a general term to signify disc displacement should be avoided. By exclusion of other terms, and by reasons of simplicity and common usage, herniated disc is the best general term to denote displacement of disc material. The term is appropriate to denote the general diagnostic category when referring to a specic disc and to be inclusive of various types of displacement when speaking of groups of discs. The term includes discs that may properly be characterized by more specic terms, such as protruded disc or extruded disc. The term herniated disc, as dened in this work, refers to localized displacement of nucleus, cartilage, fragmented apophyseal bone, or fragmented anular tissue beyond the intervertebral disc space (disc space, interspace). The interspace is dened, craniad and caudad, by the vertebral body endplates and, peripherally, by the edges of the vertebral ring apophyses, exclusive of osteophytic formations. This denition was deemed more practical, especially for interpretation of imaging studies, than a pathologic denition requiring identication of disc material forced out of normal position through an anular defect. Displacement of disc material, either through a fracture in the bony endplate or in conjunction with displaced fragments of fractured walls of the vertebral body, may be described as herniated, disc, although such description should accompany description of the fracture so as to avoid confusion with primary herniation of disc material. Displacement of disc materials from one location to another within the interspace, as with intra-anular migration of nucleus without displacement beyond the interspace, is not considered herniation. To be considered herniated, disc material must be displaced from its normal location and not simply represent an acquired growth beyond the edges of the apophyses, as is the case when connective tissues develop in gaps between osteophytic formations. Displacement, therefore, can only occur in association with disruption of the normal anulus or, as in the case of intravertebral herniation (Schmorls node), a break in the vertebral body endplate. Since details of the integrity of the anulus are often unknown, the distinction of herniation is usually made by observation of displacement of disc material beyond the edges of the ring apophyses that is localized, meaning less than 50% (180 degrees) of the circumference of the disc. Generalized, meaning greater than 50%, displacement of disc material beyond the ring apophyses, or adaptive changes of the apophyses and/or outer anulus to adjacent abnormality, such as may occur with scoliosis or spondylolisthesis, are not herniations. The 50% cut-off line is established by way of convention to lend precision to terminology and does not demarcate etiology, relation to symptoms, or treatment indications. The term bulge refers to an apparent generalized extension of disc tissues beyond the edges of the apoph-
yses. Such bulging occurs in greater than 50% of the circumference of the disc and extends a relatively short distance, usually less than 3 mm, beyond the edges of the apophyses. Bulge describes a morphologic characteristic of various possible causes. Bulge is a term for an image that requires a differential diagnosis. Bulging is sometimes a normal variant (usually at L5-S1); can result from advanced disc degeneration or from vertebral body remodeling (as consequent to osteoporosis, trauma, or adjacent structural deformity); can occur with ligamentous laxity in response to loading or angular motion; can be an illusion caused by posterior central subligamentous disc protrusion; or can be an illusion from volume averaging (particularly with CT axial images). Bulging, by denition, is not a herniation. Herniation is present if there is localized displacement of disc material, and not simply outward overlapping, as is the case with some types of bulging. Application of the term bulging to a disc does not imply any knowledge of etiology, prognosis, or need for treatment or necessarily imply the presence of symptoms. A disc may have more than one herniation. A disc herniation may be present along with other degenerative changes, fractures or other abnormalities of adjacent bone, or other abnormalities of the disc. The term herniated disc does not imply any knowledge of etiology, relation to symptoms, prognosis, or need for treatment. When data are sufcient to make the distinction, a herniated disc may be more specically characterized as protruded or extruded. These distinctions are based on the shape of the displaced material. They do not imply knowledge of the mechanism by which the changes occurred and, thereby, differ from denitions that base the distinction on whether and how disc material has passed through a defect in the anulus.Protruded Discs A disc is protruded, if the greatest plane, in any direction, between the edges of the disc material beyond the disc space is less than the distance between the edges of the base, when measured in the same plane. The term protrusion is only appropriate in describing herniated disc material, as discussed above. Protrusions may be focal or broad-based. The distinction between focal and broad-based is arbitrarily set at 25% of the circumference of the disc. Protrusions with a base less than 25% (90 degrees) of the circumference of the disc are focal. If disc material is herniated so that the protrusion encompasses 25% to 50% of the circumference of the disc, it is considered broad-based protrusion. Extruded Discs The term extruded is consistent with the lay language meaning of material forced from one domain to another through an aperture. With reference to a disc, the test of extrusion is the judgment that, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base measured in the same plane; or when no continuity exists between the
disc material beyond the disc space and that within the disc space. Extruded disc material that has no continuity with the disc of origin may be further characterized as sequestrated. A sequestrated disc is a subtype of extruded disc but, by denition, can never be a protruded disc. Disc material that is displaced away from the site of extrusion, regardless of continuity, may be called migrated, a term that is useful for the interpretation of imaging studies because it is often impossible from images to know if continuity exists. The use of the distinction between protrusion and extrusion is optional and some observers may prefer to use, in all cases, the more general term herniation. Further distinctions can often be made regarding containment, continuity, volume, composition, and location of the displaced disc material.Containment/Continuity Herniated disc material can be contained or uncontained. The test of containment is whether the displaced disc tissues are wholly held within intact outer anulus. A disc with a contained herniation would not leak into the vertebral canal uid that has been injected into the disc. Although the posterior longitudinal ligament and/or peridural membrane may partially cover extruded disc tissues, such discs are not considered contained unless the outer anulus is intact. Strictly speaking, containment refers to the integrity of the outer anulus covering the disc herniation. The technical limitations of currently available noninvasive imaging modalities (CT and MRI) usually preclude the distinction of a contained from an uncontained disc herniation. Discography does not allow one to distinguish a containing capsule consisting of both anular bers and longitudinal ligament bers from one consisting only of longitudinal ligament bers, and essentially only allows one to separate a leaking disc from a nonleaking disc. Displaced disc fragments are sometimes characterized as free. A free fragment is synonymous with a sequestrated fragment and not the same as uncontained, as the latter refers only to the integrity of the outer anulus and has no inference as to the continuity of the displaced disc material with the parent disc. A fragment should be considered free, or sequestrated, only if there is no remaining continuity of disc material between it and the disc of origin. The term migrated disc or fragment refers to displacement of disc material away from the opening in the anulus through which the material has extruded. Some migrated fragments will be sequestrated, but the term migrated refers only to position and not to continuity. Referring to the posterior longitudinal ligament (PLL), some authors have distinguished displaced disc material as subligamentous, extraligamentous, transligamentous, or perforated. When the distinction between the outer anulus and the PLL is unclear and a fragment is under such a blended structure (sometimes called capsule), it has been called subcapsular. If the peridural membrane alone surrounds the displaced disc
material, the displacement is sometimes called submembranous. Such permutations of continuity, containment, and relationships to ligaments and membranes are renements that may suit certain purposes but do not supersede the basic denition of disc herniation and the major subcategorizations of extrusion and protrusion.Volume and Composition of Displaced Material A scheme to dene the degree of canal compromise produced by disc displacement should be practical, objective, reasonably precise, and clinically relevant. A simple scheme that fullls the criteria utilizes measurements taken from an axial section at the site of the most severe compromise. Canal compromise of less than one third of the canal at that section is mild; between one and two thirds is moderate; and over two thirds is severe. The same grading can be applied for foraminal involvement. Such characterizations of volume describe only the cross- sectional area at one section and do not account for total volume of displaced material, proximity to, compression and distortion of neural structures, or other potentially signicant features, which the observer may further detail by narrative description. Composition of the displaced material may be characterized by such terms as nuclear, cartilaginous, bony, calcied, ossied, collagenous, scarred, desiccated, gaseous, or liqueed. Clinical signicance related to the observation of volume and composition depends on correlation with clinical data and cannot be inferred from morphologic data alone. Location Bonneville proposed a useful and simple alpha-numerical system to classify, according to location, the position of disc fragments that have migrated in the horizontal or sagittal plane.2,3 Using anatomic boundaries familiar to surgeons, Wiltse proposed another system.15,45 Anatomic zones and levels are dened using the following landmarks: medial edge of the articular facets; medial, lateral, upper, and lower borders of the pedicles; and coronal and sagittal planes at the center of the disc (Figure 14). On the horizontal (axial) plane, these landmarks determine the boundaries of the central zone, the subarticular zone, the foraminal zone, the extraforaminal zone, and the anterior zone, respectively (Figure 15). On the sagittal (craniocaudal) plane, they determine the boundaries of the disc level, the infra-pedicular level, the pedicular level, and the supra-pedicular level, respectively (Figure 16). The method is not as precise as drawings depict because borderlines such as the medial edges of facets and the walls of the pedicles are curved, but the method is simple, practical, and in common usage. Moving from central to right lateral in the axial (horizontal) plane, location may be dened as central, right central, right subarticular, right foraminal, or right extraforaminal. The term paracentral is less precise than dening right central or left central,
Figure 14. Coronal drawing illustrating the main anatomic zones and levels. (Reprinted with permission.45)
but is useful in describing groups of discs that include both, or when speaking informally when the side is not signicant. For reporting of image observations of a specic disc, right central or left central should supersede use of the term paracentral. The term far lateral is sometimes used synonymously with extraforaminal. In the sagittal plane, location may be dened as discal, infra-pedicular, supra-pedicular, or pedicular. In the coronal plane, anterior, in relationship to the disc, means ventral to the midcoronal plane of the centrum. Reporting When interpretations are made using clinical data, the nature of the clinical data and degree of condence in them may be appropriate parts of the report. The report should distinguish interpretations that are made on purely morphologic grounds from those using clinical data. The sources of the morphologic data should be described. Reports should classify each disc examined into broad diagnostic categories. Further specicity may be appro-
priate depending on the data and the purpose of the examination. The ability to distinguish between various forms of herniation and between broad-based protrusion and bulging depends on the adequacy of available imaging data and the judgment of the interpreter. Likewise, knowing whether there is a thin thread of continuity between displaced disc material and disc of origin, or whether there is a small lapse in the integrity of the outer bers of anulus, may not be possible, except by surgical observation. Interpretations are made with various degrees of condence. Statement of the degree of condence is an important component of communication. The reporter should characterize the interpretation as Denite if there is no doubt, Probable if there is some doubt but the likelihood is greater than 50%, and Possible if there is reason to consider but the likelihood is less than 50%. The source and quality of the data are important qualiers of the degree of condence. It may be appropriate to characterize the interpretation with one degree of condence based on morphologic criteria and another if clinical data are considered. If the interpreter has in-
Figure 15. Schematic representation of the anatomic zones identied on axial images. The anterior zone (not illustrated) is delineated from the extraforaminal zone by an imaginary coronal line in the center of the vertebral body. (Adapted with permission.45)
formation enough to do so, he or she may further suggest that the imaging ndings are, or are not, related to the patients symptoms, but the descriptive terms and diagnostic categories proposed in this model are not meant to infer any relationship to symptoms or need for treatment. Suggestions for additional studies to improve the level of condence are often appropriate. Coding The International Classication of Diseases (ICD) has been published under various names since 1900. Beginning in 1948, the World Health Organization (WHO) revised ICD approximately every 10 years. The 9th Revision (ICD-9)45 was due for revision in 1987, but the rst volume, the Tabular List, of the revision (ICD-10) was not prepared until 1992 and, as of 2000, has not been implemented in the United States. In practice, most coding in the United States follows a modication, the International Classication of Diseases, 9th Revision, Clinical Modication (ICD-9-CM),42 which is ofcially updated in October of each year. Attempts to provide more specic coding for spinal disorders, such as that of the North American Spine Society,13 have not been widely utilized because medical care providers and hospitals must use ICD-9-CM for reimbursement from government and private insurers. A modication of WHOs Fascicle V, Surgical Procedures, called the ICD-9-CM Procedure Classication,
published as Volume 3 to ICD-9-CM,42 is used in the United States primarily by hospitals for coding procedures and complications that occur during hospitalization. Its validity has been studied with regard to spine procedures.10,11 In the United States, for coding of examination, management, and procedures to care for spinal disorders, most physicians use the Current Procedural Terminology (CPT), 1 updated yearly by the American Medical Association. In ICD-9-CM, the three-digit diagnosis code 722. is termed Intervertebral disc disorders. A fourth digit, following the decimal is used variously to specify site or type of pathology. The rst four subcategorizations (722.0, 722.10, 722.11, and 722.2) are for cervical, thoracic, lumbar, or site-unspecied Displacement of intervertebral disc without myelopathy. Listed as Instructional Notations, by way of examples of what may be included, are Discogenic Syndrome, Herniation of Nucleus Pulposus, Intervertebral Disc Extrusion, Prolapse, Protrusion, Rupture, and Neuritis or Radiculitis due to displacement or rupture of intervertebral disc. The fourth subcategorization, 722.3, is designated Schmorls nodes. Subcategorizations 722.4, 722.5, and 722.6 are for Degeneration of Intervertebral Disc in the cervical, thoracic or lumbar, and unspecied regions, respectively. Instructional Notations specify inclusion of degenera-
Figure 16. Schematic representation of the anatomic levels identied on cranio-caudal images. (Adapted with permission.45)
tive disc disease and narrowing of intervertebral disc or space. Subcategorization 722.7 is labeled Intervertebral disc disorder with myelopathy. It does not specify displacement of the disc. Fifth digits are added for regional location. Subcategorization 722.8 is labeled Postlaminectomy syndrome. Other and unspecied disc disorder is the diagnostic label of 722.9, with Instructional Notations to include calcication of intervertebral cartilage or disc and Discitis. Observations of imaging variations of unknown signicance can be coded 793.7, which ICD9-CM describes as Nonspecic abnormal ndings on radiologic and other examination of body structure, Musculoskeletal. The International Classication of Diseases, 10th revision, lists intervertebral disc disorders under the Other Dorsopathies Section. Digits after the decimal for codes M50. and M51. provide separate codes for cervical or lumbar/thoracic disc disorder with myelopathy, disc disorder with radiculopathy, other disc displacement, other disc degeneration, other disc disorders, and Schmorls nodes. Translation of the disc nomenclature recommended here into ICD-9-CM codes presents relatively little difculty. Discs characterized herein as herniated should be coded under 722.0, 722.10, 722.11, or 722.2. A disc described as bulging without further specication as to the cause of the bulging should not be coded as a displacement, but, like other observations of uncertain signicance as 722.9 other and unspecied disc disorder or as 793.7, nonspecic abnormal ndings on radiographic examination (musculoskeletal). Intravertebral herniation (Schmorls node) should be coded 722.3. Although ICD-9-CM language characterizing intervertebral disc disorder with myelopathy does not specify that the disc is displaced, that is the logical implication, so it is better to code a displaced disc causing myelopathy as 722.7, rather than choose 722.0/1/2, which would introduce the contradictory language of without myelopathy. Various permutations of disc degeneration should be coded 722.4/5/6 and can be added, where appropriate, to codes that describe displacement. Nonspecic discitis and other not-elsewhere-classied disc disorders should be coded 722.9; except, of course, when specic pathogens, neoplastic disorders, or nondegenerative arthridites are known, in which case the specic diagnosis should be used, instead of, or in addition to, 722.9. Translation of recommended terminology into ICD-10 is also fairly straightforward and follows the same principles. The International Classication of Diseases, 10th revision, takes the demands on clinical knowledge a step further by providing separate codes for disc disorder with radiculopathy (M50.1, M51.1), disc disorder with myelopathy (M50.0, M51.0), and other disc displacement (M50.2, M51.2). The emphasis is on the clinical neurologic status with disorder and displacement being used almost synonymously,
which contrasts with the aim of nomenclature to provide specicity to disc pathology and morphology. The differing axes of coding and terminology requirements are best bridged by assuming that disc herniations are coded as other disc displacement unless known to accompany radiculopathy or myelopathy, in which case they are best coded as disc disorder with radiculopathy or disc disorder with myelopathy. Like ICD-9-CM, ICD-10 provides specic codes for Schmorls nodes (M51.4) and for disc degeneration (M50.3, M51.3). ICD-10 provides separate codes for other specied intervertebral disc disorders(M50.8, M51.8) and for intervertebral disc disorder, unspecied (M50.9, M51.9). Sciatic pain, lumbago, regional spinal pain syndromes, and radiculopathies and myelopathies not known to be caused by disc herniation are provided unique codes in both ICD-9-CM and ICD-10. Codes for disc disorders or displacements should only be used when a diagnosis of abnormal disc morphology is intended. Procedural coding systems present little challenge to diagnostic nomenclature, since diagnoses are inferred but not dened by procedural codes. CPT provides codes for examination, management, and procedural services, including, in some instances the naming of diagnoses to help dene the procedure; for example, operations to remove displaced disc material are characterized as excision of herniated intervertebral disc or as diskectomy, as descriptors of certain procedures done through a laminotomy or laminectomy approach (63001-63048). Procedure 62287 is characterized as aspiration procedure, percutaneous, of nucleus pulposus of intervertebral disc. Glossary
Note Some terms and denitions included in this Glossary are not recommended as preferred terminology but are included to facilitate interpretation of vernacular and, in some cases, improper use. Preferred denitions are listed rst. Confusing or inaccurate alternative denitions are placed in brackets and designated as Non-Standard.aging disc Disc demonstrating features of normal aging. Spondylosis deformans possibly represents the normal aging process. anterior displacement Displacement of disc tissues beyond the disc space into the anterior zone. anterior zone Peridiscal zone that is anterior to the midcoronal plane of the vertebral body. anulus, annulus (abbreviated form of annulus fibrosus) A multilaminated ligament surrounding the periphery of each disc space, attaching, craniad and caudad, to endplate cartilage and ring apophyseal bone and blending centrally with nucleus pulposus. Note: Either anulus or annulus is correct spelling. Nomina Anatomica uses both forms, whereas Terminologia Anatomica states anulus
brosus.18,21 Fibrosus has no correct alternative spelling; brosis has a different meaning and is incorrect in this context.asymmetric bulge Presence of outer anulus beyond the
should be diagnosed as herniation or, when appropriate, as specic types of herniation. See: herniated disc, protruded disc, extruded disc.capsule Combined bers of anulus and posterior lon-
plane of the disc space, more evident in one section of the periphery of the disc than another, but not sufciently focal to be characterized as a protrusion. Note: Asymmetric bulge is a morphologic observation of various potential causes and is not a diagnosis. See: bulge.balloon disc (colloquial) Diffuse displacement of nucleus through the vertebral endplate, commonly seen in severe osteoporosis. base (of displaced disc) The cross-sectional area of disc material at the outer margin of the disc space of origin, where disc material beyond the disc space is continuous with disc material within the disc space. In the craniocaudal direction, the length of the base cannot exceed, by denition, the height of the intervertebral space. broad-based protrusion Protrusion of disc material extending beyond the outer edges of the vertebral body apophyses over an area greater than 25% (90 degrees) and less than 50% (180 degrees) of the circumference of the disc. See protrusion. Note: Broad-based protrusion refers only to discs in which disc material has displaced in association with localized disruption of the anulus and not to generalized (over 50% or 180 degrees) apparent extension of disc tissues beyond the edges of the apophyses. If the base is less than 25%, it is called focal protrusion. Apparent extension of disc material, formation of additional connective tissue between osteophytes, or overlapping of nondisrupted tissue beyond the edges of the apophyses of over 50% of the circumference of the disc may be described as bulging. See: bulging disc, focal protrusion. bulging disc, bulge (n), bulge (v). 1. A disc in which the contour of the outer anulus extends, or appears to extend, in the horizontal (axial) plane beyond the edges of the disc space, usually over greater than 50% (180 degrees) of the circumference of the disc and usually less than 3 mm beyond the edges of the vertebral body apophyses. 2. (Non-Standard) [A disc in which the outer margin extends over a broad base beyond the edges of the disc space.] 3. (Non-Standard) [Mild, smooth displacement of disc, whether focal or diffuse.] 4. (NonStandard) [Any disc displacement at the discal level.] Note: Bulging is an observation of the contour of the outer disc and is not a specic diagnosis. Bulging has been variously ascribed to redundancy of anulus secondary to loss of disc space height, ligamentous laxity, response to loading or angular motion, remodeling in response to adjacent pathology, unrecognized and atypical herniation, and illusion from volume averaging on CT axial images. Bulging may or may not represent pathologic change, physiologic variant, or normalcy. Bulging is not a form of herniation; discs known to be herniated
gitudinal ligament. Note: The interface between outer anulus and posterior longitudinal ligament can be indistinguishable, making useful the term capsule and the derivative subcapsular, which refers to disc tissue beneath the capsule.cavitation Spaces, cysts, clefts, or cavities formed within the nucleus and inner anulus from disc degeneration. central zone Zone within the vertebral canal between sagittal planes through the medial edges of each facet. Note: The center of the central zone is a sagittal plane through the center of the vertebral body. The zones to either side of the center plane are right central and left central, which are preferred terms when the side is known, as when reporting imaging results of a specic disc. When the side is unspecied, or grouped with both right and left represented, the term paracentral is appropriate. chondrosis
chronic disc herniation Disc herniation with presence of calcication, ossication, or gas accumulation within the displaced disc material, suggesting that the herniation is not of recent origin. Note: The term implies the presence of calcication, ossication, or gas accumulation and should not be used for herniations of soft disc material, regardless of the duration of displacement. See: degenerated disc, hard disc. claw osteophyte Bony outgrowth arising very close to the disc margin, from the vertebral body apophysis, directed, with a sweeping conguration, toward the corresponding part of the vertebral body opposite the disc. collagenized disc or nucleus A disc in which the mucopolysaccharide of the nucleus has been replaced by brous tissue. communicating disc, communication (n), communicate (v)
Interruption in the periphery of the disc, so that uid injected into the disc space could ow into the vertebral canal and thus into contact with displaced disc material. Note: Communication refers to the status of displaced disc tissues with reference to the parent disc. Containment refers to the integrity of the anulus as container of disc tissues. Uncontained, displaced disc tissues could be noncommunicating if the displaced tissue is sealed off by peridural membrane or by healing of the tear in the anulus.concentric tear Tear or ssure of the anulus characterized by separation, or break, of anular bers, in a plane roughly parallel to the curve of the periphery of the disc,
creating uid-lled spaces between adjacent anular lamellae. See: radial tears, transverse tears.contained herniation, containment (n), contain (v) 1. Displaced disc tissue that is wholly within an outer perimeter of uninterrupted outer anulus or capsule. 2. (Nonstandard) [A disc with its contents mostly, but not wholly, within anulus or capsule.] 3. (Non-Standard) [A disc with displaced elements contained within any investiture of the vertebral canal.] Note: The preferred meaning encompasses disc tissues that are enclosed by distended portions of the outer anulus or composite of bers of the anulus and posterior longitudinal ligament. A disc whose substance is less than wholly contained by anulus is uncontained, as is a disc outside of anular bers but under a distinct posterior longitudinal ligament or peridural membrane. Designation of a disc as contained, or uncontained, should dene the integrity of the anulus enclosing the disc, although such distinction may not be possible with currently available imaging methods. continuity 1. Connection of displaced disc tissue by a bridge of disc tissue, however, thin, to tissue within the disc of origin. 2. (Non-Standard) [Connection of displaced displaced disc tissue by a substantial bridge of disc tissue to disc within the disc of origin]. 3. (NonStandard) [Connection of displaced disc tissue by any tissue to disc tissue within the disc or origin.] Note: Tenuous attachments, beyond recognition by most imaging methods, may have signicance to the surgeon or endoscopist. Bridges of peridural membrane, or scar, do not represent continuity. See sequestration. Crock disc See internal disc disruption syndrome. degenerated disc, degeneration (n), degenerate (v) 1. Changes in a disc characterized by desiccation, brosis and cleft formation in the nucleus, ssuring and mucinous degeneration of the anulus, defects and sclerosis of endplates, and/or osteophytes at the vertebral apophyses. 2. Imaging manifestations commonly associated with such changes. 3. (Non-Standard) [Changes in a disc related to aging.] Note: Either of the rst two denitions may be correct, depending on context. Clinical features must be considered to determine whether degenerative changes are pathologic and what may or may not have contributed to their development. The term degenerated disc, in itself, does not infer knowledge of cause, relationship to aging, presence of symptoms, or need for treatment. See intervertebral osteochondrosis, spondylosis, spondylosis deformans. degenerative disc disease 1. A clinical syndrome characterized by manifestations of disc degeneration and symptoms thought to be related to those changes. 2. (Non-Standard) [Abnormal disc degeneration.] 3. (NonStandard) [Imaging manifestations of degeneration greater than expected, considering the age of the patient]. Note: Causal connections between degenerative
changes and symptoms are often difcult clinical distinctions. The term carries implications of illness that may not be appropriate if the only manifestations are from imaging. The preferred term for description of imaging manifestations alone, or imaging manifestations of uncertain relationship to symptoms, is degenerated disc rather than degenerative disc disease.delamination Separation of anular bers along planes parallel to the periphery of the disc, thought to represent separation of laminated layers of the outer anulus brosus. desiccated disc 1. Disc with reduced water content,
usually primarily of nuclear tissues. 2. Imaging manifestations of reduced water content of the disc; or apparent reduced water content, as from alterations in the concentration of hydrophilic glycosaminoglycans.disc (disk) Complex structure composed of nucleus, anulus, cartilaginous endplates, and vertebral body ring apophyseal attachments of anulus. Note: Most English language publications use the spelling disc more often than disk.12 Nomina Anatomica designates the structures as Disci intervertebrales and Terminologia Anatomica as discus intervertebralis/Intervertebral disc.18,21 disc of origin Disc from which a displaced fragment originated. Syn: parent disc Note: Since displaced fragments often contain tissues other than nucleus, disc of origin is preferred to nucleus of origin. Parent disc is synonymous, but more colloquial. disc space Space limited, craniad and caudad, by the endplates of the vertebrae and peripherally by the edges of the vertebral body ring apophyses exclusive of osteophytes. Syn: intervertebral disc space. disc space height The distance between the planes of the endplates of the vertebrae craniad and caudad to the disc. discal level Level of the vertebral canal between axial planes through the bony endplates of the vertebrae craniad and caudad to the disc. discogenic vertebral sclerosis Increased bone density and calcication adjacent to the endplates of the vertebrae craniad and caudad to a degenerated disc, usually a manifestation of intervertebral osteochondrosis. displaced disc A disc in which disc material is beyond the outer edges of the vertebral body ring apophyses (exclusive of osteophytes) of the craniad and caudad vertebrae, or, as in the case of intravertebral herniation, penetrated through the vertebral body endplate. Note: Displaced disc is a general term that does not imply knowledge of the underlying pathology, cause, relationship to symptoms, or need for treatment. The term includes, but is not limited to, disc herniation and disc migration. See: herniated disc, migrated disc.
Lumbar Disc Pathology: Recommendations North American Spine Society et al E107 epidural membrane See peridural membrane. extraforaminal zone The zone beyond the sagittal plane of the lateral edges of the pedicles, having no welldened lateral border. Syn: far lateral zone, far-out zone. extraligamentous Posterior or lateral to the posterior longitudinal ligament. Note: Extraligamentous disc refers to displaced disc tissue that is located lateral, or posterior to, the posterior longitudinal ligament. If the disc has extruded through the posterior longitudinal ligament it is sometimes called transligamentous or perforated, and if through the peridural membrane, it is sometimes rened to transmembranous. extruded disc, extrusion (n), extrude (v) A herniated disc in which, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base in the same plane; or when no continuity exists between the disc material beyond the disc space and that within the disc space. Note: The preferred denition is consistent with the common language image of extrusion as an expulsion of material from a container through and beyond an aperture. Displacement beyond the outer anulus of disc material with any distance between its edges greater than the distance between the edges of the base distinguishes extrusion from protrusion. Distinguishing extrusion from protrusion by imaging is best done by measuring the edges of the displaced material and remaining continuity with the disc of origin, whereas relationship of the displaced disc material to the aperture through which it has passed is more readily observed surgically. Characteristics of protrusion and extrusion may coexist, in which case the disc should be subcategorized as extruded. Extruded discs in which all continuity with the disc of origin is lost may be further characterized as sequestrated. Disc material displaced away from the site of extrusion may be characterized as migrated. See: herniated disc, migrated disc, protruded disc. fissure of anulus Separations between anular bers, avulsion of bers from their vertebral body insertions, or breaks through bers that extend radially, transversely, or concentrically, involving one or more layers of the anular lamellae. Syn: tear of anulus, torn anulus. Note: The terms ssure and tear are commonly used synonymously. Neither term implies any knowledge of etiology, relationship to symptoms, or need for treatment. Tear or ssure are both used to represent separations of anular bers from causes other than sudden violent injury to a previously normal anulus, which can be appropriately termed rupture of the anulus, which, in turn, contrasts to the colloquial, nonstandard, use of the term ruptured disc, referring to herniation. focal protrusion Protrusion of disc material so that the base of the displaced material is less than 25% (90 degrees) of the circumference of the disc. Note: Focal protrusion refers only to herniated discs that are not ex-
truded and do not have a base greater than 25% of the disc circumference. Protruded discs with a base greater than 25% are broad-based protrusions.foraminal zone The zone between planes passing through the medial and lateral edges of the pedicles. Note: The foraminal zone is sometimes called the pedicle zone, which can be confusing because pedicle zone might also refer to measurements in the sagittal plane between the upper and lower surface of a given pedicle, which is properly called the pedicle level. The foraminal zone is also sometimes called lateral zone, which can be confusing because lateral zone can also mean extraforaminal zone or an area including both the foraminal and extraforaminal zones. free fragment 1. A fragment of disc that has separated from the disc of origin and has no continuous bridge of disc tissue with disc tissue within the disc of origin. Syn: sequestrated disc 2. (Non-Standard) [A fragment that is not contained within the outer perimeter of the anulus.] 3. (Non-Standard) [A fragment that is not contained within anulus, posterior longitudinal ligament, or peridural membrane.] Note: Sequestrated disc and free fragment are virtually synonymous. When referring to the condition of the disc, categorization as extruded with subcategorization as sequestrated is preferred, whereas free fragment or sequestrum is appropriate when referring specically to the fragment. hard disc Disc displacement in which the displaced portion has undergone calcication or ossication and may be intimately associated with apophyseal osteophytes. Note: The term hard disc is most often used in reference to the cervical spine to distinguish chronic hypertrophic and reactive changes in the periphery of the disc from acute extrusion of soft, predominantly nuclear tissue. See: chronic disc herniation. herniated disc, herniation (n), herniate (v) 1. Localized displacement of disc material beyond the normal margins of the intervertebral disc space. 2. (Non-Standard) [Any displacement of disc tissue beyond the disc space]. Note: Localized means, by way of convention, less than 50% (180 degrees) of the circumference of the disc. Disc material may include nucleus, cartilage, fragmented apophyseal bone, or fragmented anular tissue. The normal margins of the intervertebral disc space are dened, craniad and caudad, by the vertebral body endplates and peripherally by the edges of the vertebral body ring apophyses, exclusive of osteophytic formations. Herniated disc generally refers to displacement of disc tissues through a disruption in the anulus, the exception being intravertebral herniations (Schmorls nodes) in which the displacement is through vertebral endplate. Herniated discs in the horizontal (axial) plane may be further subcategorized as protruded or extruded. Herniated disc is sometimes referred to as herniated nucleus pulposus, but the term herniated disc is preferred because displaced disc tissues often include cartilage, bone fragments, or
anular tissues. The term ruptured disc is used synonymously with herniated disc, but is more colloquial and can be easily confused with violent, traumatic rupture of the anulus or endplate. The term prolapse has also been used as a general term for disc displacement, but its use has been inconsistent. The term herniated disc does not infer knowledge of cause, relation to injury or activity, concordance with symptoms, or need for treatment.herniated nucleus pulposus (HNP) See herniated disc. high intensity zone (HIZ) Area of high signal intensity on
See intra-anular
displacement.intradural herniation A disc from which displaced tissue has penetrated, or become enclosed by, the dura so that it lies within the thecal sac. intravertebral herniation A disc in which a portion of the disc is displaced through the endplate into the centrum of the vertebral body. Syn: Schmorls node. lateral membrane See peridural membrane. lateral recess See subarticular zone. lateral zone See foraminal zone. limbus fracture Traumatic separation of a segment of bone from the edge of the vertebral ring apophysis at the site of anular attachment. Note: Limbus fractures of various types may be accompanied by disc herniation, usually by either focal or broad-based protrusion. They may occur into the anterior zone or posteriorly into the zones where they may compress neural tissues. limbus vertebrae Separation of a segment of rim of vertebral body ring apophysis. Note: Limbus vertebrae may result from fracture or from developmental abnormalities. Limbus vertebrae is commonly seen in patients who have had Scheuermanns disease. The lesions may be called rim lesions. The term is derived from the Latin nominative limbus and genitive modier vertebrae, thus is singular. marginal osteophyte Osteophyte that protrudes from and beyond the outer perimeter of the vertebral endplate apophysis. marrow changes (of vertebral body) See vertebral body marrow changes (Modic classication). migrated disc, migration (n), migrate 1. Herniated disc in which a portion of extruded disc material is displaced away from the tear in the outer anulus through which it has extruded. 2. (Non-Standard) [A herniated disc with a free fragment or sequestrum beyond the disc level.] Note: Migration refers to the position of the displaced disc material, rather than to its continuity with disc tissue within the disc of origin; therefore, it is not synonymous with sequestration. Modic Type 1,2,3 See vertebral body marrow changes. nonmarginal osteophyte Osteophyte occurs at sites other than the vertebral endplate apophysis. See: marginal osteophyte. normal disc 1. A fully and normally developed disc with no changes attributable to trauma, disease, degeneration, or aging. The bilocular appearance of the adult nucleus is considered a sign of normal maturation. 2. (Non-Standard) [A disc that may contain one or more morphologic variants which would be considered normal given the clinical circumstances of the patient.].
T2-weighted magnetic resonance images of the disc, usually referring to the outer anulus. Note: High intensity zones within the posterior anular substance may reect ssure or tear of the anulus, but do not imply knowledge of etiology, concordance with symptoms, or need for treatment.infra-pedicular level The level between the axial planes of the inferior edge of the pedicle craniad to the disc in question and the inferior endplate of the vertebral body above. Syn: superior vertebral notch. internal disc disruption Disorganization of structures
drosis.intervertebral disc See disc. intervertebral disc space See disc space. intervertebral osteochondrosis Degenerative process of
the spine involving the vertebral body endplates, the nucleus pulposus, and the anulus brosus, which is characterized by disc space narrowing, vacuum phenomenon, and vertebral body reactive changes. Syn: deteriorated disc, chronic discopathy, osteochondrosis.intra-anular displacement Displacement of central, predominantly nuclear, tissue to a more peripheral site within the disc space, usually into a ssure in the anulus. Syn: (Non-Standard) [intra-anular herniation], [intradiscal herniation]. Note: Intra-anular displacement is distinguished from disc herniation, in that herniation of disc refers to displacement of disc tissues beyond the disc space. Intra-anular displacement is a form of internal disruption. When referring to intra-anular displacement, it is best not to use the term herniation in order to avoid confusion with disc herniation. intra-anular herniation (Non-Standard)
Note: Many congenital and developmental variations may be normal in that they are not associated with symptoms, certain adaptive changes in the disc may be normal considering adjacent pathology, and certain degenerative phenomena may be normal given the patients age; however, classication and reporting for medical purposes is best served if such discs are not considered normal. What is clinically normal for a given patient is a clinical judgment independent of the need to describe any variation in the disc itself.nucleus of origin The central, nuclear portion of the disc of reference, usually used to reference the disc from which tissue has been displaced. Syn: parent nucleus, disc of origin. osteochondrosis See intervertebral osteochondrosis. osteophytes Focal hypertrophy of bone surface and/or ossication of soft tissue attachments to the bone. paracentral In the right or left central zone of the vertebral canal. See central zone. Note: The terms right central or left central are preferable when speaking of a single site when the side can be specied, as when reporting the ndings of imaging procedures. Paracentral is appropriate if the side is not signicant or when speaking of mixed sites. parent disc See disc of origin. parent nucleus See nucleus of origin, disc of origin. pedicular level The level between axial planes through the upper and lower edges of the pedicle. Note: The pedicular level may be further designated with reference to the disc in question as pedicular level above or pedicular level below. Distinction should be made between designation of the pedicular level in the sagittal plane and the foraminal zone which is dened by the planes of the medial and lateral walls of the pedicles in the axial plane. Syn: peduncular level. peduncular See pedicular. perforated (Non-Standard) See transligamentous. peridural membrane A delicate, translucent membrane that attaches to the undersurface of the deep layer of the posterior longitudinal ligament, and extends laterally and posteriorly, encircling the bony spinal canal outside the dura. The veins of Batsons plexus lie on the dorsal surface of the peridural membrane and pierce it ventrally. Syn: lateral membrane, epidural membrane. prolapsed disc, prolapse (n), prolapse (v) (Nonstandard) 1. A herniated disc in which disc tissue has protruded or extruded at the level of the disc and below into the suprapedicular level. 2. (Nonstandard) [Any herniated disc.] Note: The term prolapse is not used widely outside of medicine. Medically, it usually means to fall out and down, as with prolapse of the rectum or uterus. Analogy to the disc would apply most closely to disc tissue that
has displaced beyond the disc space into the suprapedicular zone. It has been used often, nonspecically, as synonymous with herniation. Prolapse is not a recommended term for description of disc displacement.protruded disc, protrusion (n), protrude (v) 1. A herniated disc in which the greatest plane, in any direction, between the edges of the disc material beyond the disc space is less than the distance between the edges of the base, when measured in the same plane. 2. (Non-Standard) [A disc in which disc tissue beyond the disc space is contained within intact anulus]. 3. (Non-Standard) [Any, or unspecied type of, disc herniation.] Note: The test of protrusion is that there must be a localized (less than 50% or 180 of the circumference of the disc) displacement of disc tissue so that the distance between the corresponding edges of the displaced portion must not be greater than the distance between the edges of the base. A disc that has broken through the outer anulus at the apex, but maintains a broad continuity at the base, is protruded and uncontained. While sometimes used as a general term in the way herniation is dened here, the use of the term protrusion is best reserved for subcategorization of herniations meeting the above criteria. See: extruded disc. radial fissure or tear Disruption of anular bers extending from the nucleus outward toward the periphery of the anulus, usually in the craniad-caudad (vertical) plane, though, at times, with occasional horizontal (transverse) components. Note: Occasionally a radial ssure extends in the transverse plane to include avulsion of the outer layers of anulus from the apophyseal ring. See: concentric tears, radial tears. rim lesion See limbus vertebrae. ruptured anulus Disruption of the bers of the anulus by sudden violent injury. Note: Separation of bers of the anulus from degeneration, repeated minor trauma, other nonviolent etiology, or when injury is simply a dening event in a degenerative process should be termed ssure or tear of the anulus. Rupture is appropriate when there is other evidence of sudden violent injury to a previously normal anulus. Ruptured anulus is not synonymous with ruptured disc, which is a colloquial equivalent of disc herniation. ruptured disc, rupture (Non-Standard) 1. A herniated disc. 2. (Non-Standard) [A disc in which the anulus has lost its integrity.] See herniated disc, ruptured anulus. Note: Ruptured disc is used colloquially to encompass the same nonspecic meaning as the preferred term herniated disc. The common, nonmedical meaning of rupture, to break apart or burst, and the medical use of rupture in the sense of complete tears of ligament or tendon are analogous to the anulus disrupted by violent injury, which may be appropriately characterized as ruptured anulus, which is not synonymous with ruptured disc.
E110 Spine Volume 26 Number 5 2001 scarred disc See collagenized disc. Schmorls node See intravertebral herniation. sequestrated disc, sequestration (n), sequestrate (v); (var: sequestered disc) An extruded disc in which a portion of subanular herniation (Non-Standard) Disc herniation in which a displaced portion is contained by anulus. Syn: contained herniation. Note: Subanular describes a herniated disc that is contained by anulus and is not synonymous with the nonherniated intra-anular displacement. See intra-anular displacement. subarticular zone The zone, within the vertebral canal, sagittally between the plane of the medial edges of the pedicles and the plane of the medial edges of the facets, and coronally between the planes of the posterior surfaces of the vertebral bodies and the under anterior surfaces of the superior facets. Syn: lateral recess, posterolateral zone Note: The subarticular zone cannot be precisely delineated because the structures that dene the planes of the zone are irregular. The lateral recess refers more appropriately to the space beneath the facet at the pedicular level than as synonymous with the entire subarticular zone. subcapsular Beneath the composite of anulus and posterior longitudinal ligament. See subligamentous. subligamentous Beneath the posterior longitudinal ligament. Note: Though the distinction between outer anulus and posterior longitudinal ligament may not always be identiable, subligamentous has meaning distinct from subanular, when the distinction can be made. When the distinction cannot be made, subcapsular is appropriate. Subligamentous contrasts to extraligamentous, transligamentous, or perforated. See extraligamentous, transligamentous.
the disc tissue is displaced beyond the outer anulus and maintains no connection by disc tissue with the disc of origin. Note: An extruded disc may be subcategorized as sequestrated if no disc tissue bridges the displaced portion and the tissues of the disc of origin. If there is a fragment of disc tissue that is not continuous with parent nucleus, but still contained, even in part, by anular tissues the disc may be characterized as protruded or extruded, but not as sequestrated. If even a tenuous connection by disc tissue remains between a displaced fragment and disc of origin, the disc is not sequestrated. If a displaced fragment has no connection with the disc of origin, but is contained within peridural membrane or under a portion of posterior longitudinal ligament that is not intimately bound with the anulus of origin, the disc is considered sequestrated. If the fragment is attached to the disc of origin by scar, or other nondiscal tissue, or is merely in apposition to the disc of origin and not connected by disc tissue, it is considered sequestrated. Sequestrated and sequestered are used interchangeably.sequestrum Disc tissue that has become displaced from the disc space of origin and lacks any continuity with disc material within the disc space of origin. Syn: disc fragment. See: sequestrated disc. Note: Sequestrum refers to the isolated fragment itself, whereas sequestrated disc denes the condition of the disc. spondylitis Inammatory disease of the spine, other than degenerative disease. Note: Spondylitis usually refers to noninfectious inammatory spondyloarthropathies. spondylosis 1. Spondylosis deformans, for which spondylosis is a shortened form. 2. (Non-Standard) Any degenerative changes of the spine that include osteophytic enlargement of apophyseal bone. Note: Spondylosis deformans has specic characteristics that distinguish it from intervertebral osteochondrosis. Both processes include vertebral body osteophytes. The term spondylosis is often used in general as synonymous with degeneration which would include both processes, but such usage is confusing, so it is best that degeneration be the general term and spondylosis deformans a specically dened subclassication of degeneration. See: degeneration, intervertebral osteochondrosis, spondylosis deformans.
Enclosed within peridural membrane. Note: With reference to displaced disc material, characterization of a herniation as submembranous usually infers that the displaced portion is extruded beyond anulus and posterior longitudinal ligament so that only the peridural membrane invests it. The peridural membrane may also enclose material injected into a leaking disc, hematoma, or abscess. See: transmembranous.submembranous supra-pedicular level The level within the vertebral canal between axial planes of the superior endplate of the vertebra caudad to the disc space in question and the superior margin of the pedicle of that vertebra. Syn: inferior vertebral notch. syndesmophytes Thin and vertically oriented bony outgrowths extending from one vertebral body to the next and representing ossication within the outer portion of the anulus brosus. tear of anulus, torn anulus See ssure of anulus and
Degenerative process of the spine involving essentially the anulus brosus and characterized by anterior and lateral marginal osteophytes arising from the vertebral body apophyses, while the intervertebral disc height is normal or only slightly decreased. See: degeneration, spondylosis.spondylosis deformans
rupture of anulus.traction osteophytes Bony outgrowth arising from the vertebral body apophysis, 23 mm above or below the edge of the intervertebral disc, projecting in a horizontal direction.
Lumbar Disc Pathology: Recommendations North American Spine Society et al E111 transligamentous Displacement, usually extrusion, of2. Bonneville JF. Plaidoyer pour une classication par limage des hernies discales lombaires: la carte-image. Rev Im Med 1990;2:557 60. 3. Bonneville JF, Dietemann JL. Limagerie dans les sciatiques; Rev Prat (Paris) 1992;42:554 66. 4. Brant-Zawadzki MN, Jensen MC. Imaging corner: Spinal nomenclature. Inter- and intra-observer variability in interpretation of lumbar disc abnormalities: A comparison of two nomenclatures. Spine 1995;20:388 90. 5. Breton G. Is that a bulging disc, a small herniation, or a moderate protrusion? Can Assoc Radiol J 1991;42:318. 6. Brock M, Patt S, Mayer HM. The form and structure of the extruded disc. Spine 1992;17:1457 61. 7. Coventry, MB, Ghormley RK, Kernohan JW. The intervertebral disc: its microscopic anatomy and pathology. J Bone Joint Surg 1945;27:105112.; 233247. 8. Czervionke LF. Lumbar intervertebral disc disease. Neuroimaging Clin North Am 1993;3:465 85. 9. Eckert C, Decker A. Pathological studies of the intervertebral discs. J Bone Joint Surg 1947;29:44754. 10. Faciszewski T, Broste SK, Fardon D. Quality of data regarding diagnoses of spinal disorders in administrative databases. J Bone Joint Surg [Am] 1997; 79:1481 8. 11. Faciszewski T, Johnson L, Noreen C, et al. Administrative databases complication coding in anterior spinal fusion procedures. What does it mean? Spine 1995;20:1783 8. 12. Fardon DF. Disc nomenclature: Current journal practices. Poster presentation, American Orthopaedic Association 110th Annual Meeting, Boca Raton, FL, June 11, 1997. 13. Fardon DF, Balderston RA, Garn SR, et al. Disorders of the Spine, A Coding System for Diagnoses. Philadelphia: Hanley and Belfus, 1991:20 2. 14. Fardon DF, Balderston RA, Garn SR, et al. Terms used for diagnosis by English speaking spine surgeons. Spine 1993;18:1 4. 15. Fardon DF, Herzog RJ, Mink JH, et al. Nomenclature of lumbar disc disorders. In: Garn SR, Vaccaro AR, eds. Orthopaedic Knowledge Update Spine. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1997: A3-A14. 16. Fardon DF, White AH, Wiesel S. Diagnostic terms and conservative treatments favored for lumbar disorders by spine surgeons in North America. Presented at the First Annual Meeting, North American Spine Society, Lake George, New York, 1986. 17. Farfan HF, Huberdeau RM, Dubow HI. Lumbar intervertebral disc degeneration: The inuence of geometrical features on the pattern of disc degenerationA post-mortem study. J Bone Joint Surg [Am] 1972;54:492510. 18. Federative Committee on Anatomic Terminology. Terminologia Anatomica. Stuttgart: George Thieme Verlag. 1998:27. 19. Herzog RJ. The radiologic assessment for a lumbar disc herniation. Spine 1996;21:19.S38S. 20. Hirsch C, Schajowicz F. Studies in structural changes in the lumbar annulus brosus. Acta Orthop Scand 1952;22:184 231. 21. International Anatomical Nomenclature Committee approved by Eleventh International Congress of Anatomists. Nomina Anatomica. 5th ed. Baltimore, MD: Waverly Press, 1983:A23. 22. Jarvik JG, Haynor DR, Koepsell TD, et al. Interreader reliability for a new classication of lumbar disc abnormalities. Acad Radiol 1996;3:537 44. 23. Kieffer SA, Stadlan EM, Mohandas A, et al. Discographic-anatomical correlation of developmental changes with age in the intervertebral disc. Acta Radiol [Diagn] (Stockholm) 1969;9:7339. 24. Masaryck TJ, Ross JS, Modic MT, et al. High resolution MR imaging of sequestered lumbar intervertebral discs. AJNR Am J Neuroradiol 1988;9: 351 8. 25. Milette PC. The proper terminology for reporting lumbar intervertebral disk disorders. AJNR Am J Neuroradiol 1997;18:1859 66. 26. Milette PC, Fontaine S, Lepanto L, et al. Differentiating lumbar disc protrusions, disc bulges, and discs with normal contour but abnormal signal intensity. Spine 1999;24:44 53. 27. Milette PC, Melanon D, Dupuis PR, et al. A simplied terminology for abnormalities of the lumbar disc. Can Assoc Radiol J 1991;42:319 25. 28. Mink JH. Terminology of lumbar spine disorders, the problem . . . and a solution. Burlingame, CA: California Managed Imaging Medical Group Publication, 1993. 29. Modic MT. Degenerative disorders of the spine. In: Magnetic Resonance Imaging of the Spine. New York: Yearbook Medical, 1989:8395. 30. Modic MT, Herfkens RJ. Intervertebral disk: Normal age-related changes in MR signal intensity. Radiology 1990;177:332 4. 31. Modic MT, Masaryk TJ, Ross JS, et al. Imaging of degenerative disk disease. Radiology 1988;168:177 86. 32. Nathan H. Osteophytes of the vertebral column. An anatomical study of
disc material through the posterior longitudinal ligament. Syn: perforated. See also extraligamentous, transmembranous.transmembranous Displacement, usually of extruded disc material, through the peridural membrane. transverse tear Tear or ssure of the anulus, running in the axial plane (horizontally), usually limited to rupture of the outer anular attachments to the ring apophysis. Note: Transverse tears are usually small and are located at the junction of the anulus and ring apophysis. They may ll with gas and, thereby, become detectable on radiographs or CT. They may be early manifestations of spondylosis deformans. More extensive radial tears may have a transverse component. See: concentric tears, radial tears. uncontained 1. Displaced disc material that is not contained by uninterrupted outer anulus. 2. (Non-Standard) [A disc in which a substantial portion of the displaced portion of the disc is outside of disc tissues.] 3. (NonStandard) [A disc in which a displaced portion is wholly outside of disc tissues]. 4. (Non-Standard) [A disc in which a displaced fragment is not contained within disc tissues, ligament, or membrane]. See discussion under contained disc. undisplaced disc A disc in which all disc material is within the intervertebral disc space. vacuum disc A disc with imaging characteristics suggestive of gas in the disc space, usually a manifestation of disc degeneration. vertebral body marrow changes (Modics classification)
Reactive vertebral body modications associated with disc inammation and degenerative disc disease, as seen on MR images. Type 1 refers to decreased signal intensity on T1-weighted spin-echo images and increased signal intensity on T2-weighted images, indicating bone marrow edema associated with acute or subacute inammatory changes. Types 2 and 3 indicate chronic changes. Type 2 refers to increased signal intensity on T1weighted images and isointense or increased signal intensity on T2-weighted images, indicating replacement of normal bone marrow by fat. Type 3 refers to decreased signal intensity on both T1 and T2-weighted images, indicating reactive osteosclerosis.vertebral notch (inferior) Incisura of the upper surface of the pedicle corresponding to the lower part of the foramen (supra-pedicular level). vertebral notch (superior) Incisura of the under surface of the pedicle corresponding to the upper part of the foramen (infra-pedicular level).
References1. American Medical Association, Current Procedural Terminology Editorial Panel. Current Procedural Terminology 2000. Chicago: American Medical Association, 2000.
34. 35.
Pierre C. Milette, MD Jeffrey S. Ross, MD Alan L. Williams, MD Jan T. Wilmink, MD, PhD
36. 37.
Members of the Task Forces Brigitte Appel, MD Neuroradiologist Head of Neuroradiology-CTMRI A.Z. Middelheim Antwerp, BelgiumJean-Francois Bonneville, MD Neuroradiologist Professor of Neuroradiology Universite de Franche-Comte Besancon, France Tom Faciszewski, MD Orthopedic Surgeon Marsheld Clinic Marsheld, WI USA Steven R. Garn, MD Orthopedic Surgeon Professor of Orthopedic Surgery University of California, San Diego San Diego, CA USA Scott Haldemann, MD, PhD Neurologist Associate Clinical Professor of Neurology University of California, Irvine Irvine, CA USA Neil Kahanovitz, MD Orthopedic Surgeon Anderson Orthopedic Clinic Arlington, VA USA Marco Leonardi, MD Neuroradiologist Head of Neuroradiology Ospedala Bellaria Bologna, Italy Jeffrey S. Ross, MD Neuroradiologist Head of Radiology Research Cleveland Clinic Cleveland, OH USA Volker K.H. Sonntag, MD Neurological Surgeon Barrow Neurological Institute Phoenix, AZ USA Alan L. Williams, MD Neuroradiologist Professor of Radiology St. Louis University St. Louis, MO USA
Appendix Chairpersons of the Task Forces David F. Fardon, MD Orthopedic Surgeon Knoxville Orthopedic Clinic Knoxville, TN USA Pierre C. Milette, MD Neuroradiologist Clinical Professor of Radiology Universite de Montre al Montreal, Quebec Canada
Clinical Task Force Tom Faciszewski, MD David F. Fardon, MD Steven R. Garn, MD Scott Haldeman, MD, PhD Neil Kahanovitz, MD Volker K.H. Sonntag, MD Imaging Task Force Brigitte Appel, MD Jean-Franc ois Bonneville, MD Marco Leonardi, MD
Jan T. Wilmink, MD, PhD Neuroradiologist Professor of Neuroradiology University of Maastricht Maastricht, The Netherlands
Jerrold H. Mink, MD Radiologist Tower Imaging Medical Group Los Angeles, CA USA John D. Simmons, MD Abercrombie Radiology Knoxville, TN USAAddress correspondence and reprint requests to Pierre C. Milette, MD Department of Radiology CHUMHpital Saint-Luc 1058, Saint-Denis Street Montreal, QC, Canada H2X 3J4 or David F. Fardon, MD Knoxville Orthopedic Clinic 1128 Weisgarber Road Knoxville, TN 37922
Consultants and Advisors Robert E. Florin, MD Neurological Surgeon Clinical Professor of Neurosurgery University of Southern California Los Angeles, CA USARichard J. Herzog,, MD Neuroradiologist Chief of Teleradiology Hospital for Special Surgery New York, NY USA