neurologic disorders
Dystonias
Classification of Dystonias
Dystonias are classified based on Etiology Clinical features Etiologyis categorized as Inherited:Has a proven genetic origin (previously known as primary) and includes disorders with autosomal dominant, autosomal recessive, mitochondrial or X-linked inheritance Idiopathic:Can be familial or sporadic Acquired:Associated with neuroanatomic abnormalities due to other disorders or drugs Clinical featuresinclude the following: Onset:Can occur at any age, from infancy to late adulthood Body distribution:May be focal (limited to one body part), segmental (involving ≥ 2 more contiguous body parts, such as the upper and lower face or face and neck), multifocal (involving ≥ 2 noncontiguous body parts, such as the neck and leg), generalized (involving the trunk plus 2 different body parts), or hemicorporal (involving half the body; also called hemidystonia) Temporal pattern:May be static, progressive, paroxysmal, or persistent and may have diurnal variability or be triggered by certain tasks (task-specific dystonia) Isolated(no evidence of another movement disorder) orcombined(accompanied by other involuntary movements [other than tremor], but predominantly dystonia) Cervical Dystonia (spasmodic torticollis)—involuntary contractions of the neck muscles—is the most common dystonia. Generalized dystonia may be inherited or secondary to another disorder or drug. Consider antipsychotic and antiemetic drugs as causes of sudden, unexplained dystonia. This rare dystonia is progressive and characterized by sustained, often bizarre postures. It is often inherited as an autosomal dominant disorder with partial penetrance due to mutations in theDYT1gene (TOR1A pathogenic variant); in some family members, the gene is minimally expressed. For example, some carriers have no symptoms (a forme fruste of the disorder) or only dystonic tremor. Symptoms of primary generalized dystonia usually begin in childhood with inversion and plantar flexion of the foot while walking. At first, the dystonia may affect only the trunk or leg but often progresses to affect the whole body, usually moving cephalad. Patients with the most severe form may become twisted into grotesque, nearly fixed postures and ultimately be confined to a wheelchair. Symptoms that begin during adulthood usually affect only the face or arms. Mental function is usually preserved. This rare dystonia (also called Segawa disease) is inherited as an autosomal dominant (DYT5a, GTP cyclohydrolase 1 gene [GTPCH1]) disorder or an autosomal recessive (DYT5b) disorder (tyrosine hydroxylase deficiency). Symptoms of dopa-responsive dystonia usually begin during childhood. Typically, one leg is affected first. As a result, children tend to walk on tiptoes. Symptoms worsen at night. Walking becomes progressively more difficult, and arms and legs are affected. However, some children have only mild symptoms, such as muscle cramps after exercise. Sometimes symptoms appear later in life and resemble those of Parkinson Disease . Movements may be slow, balance may be difficult to maintain, and a tremor may occur in the hands during rest. Symptoms lessen dramatically when low doses oflevodopaare used. Iflevodoparelieves the symptoms, the diagnosis is confirmed. Focal dystonias affect a single body part. They typically start during adulthood, after age 20 to 30 years. Initially, the posturing may be intermittent or task-specific (and thus is sometimes described as spasms). The movements tend to be more prominent during action and less so at rest, but these differences lessen over time, often resulting in distortion of the affected body part and severe disability. However, pain is uncommon except in focal primary dystonia of the neck (cervical dystonia) and in the dystonias that occur when response tolevodopastarts to wear off in Parkinson disease (most often affecting the lower limb, eg, causing inversion of the foot). Occupational dystoniaconsists of task-specific focal dystonic spasms triggered by performing skilled acts (eg, writer’s cramp, musician´s dystonia, the yips in golfers). Spasmodic dysphoniaconsists of a strained, hoarse, or creaky voice due to focal dystonia of the laryngeal muscles. Cervical dystoniamanifests with involuntary tonic contractions or intermittent spasms of neck muscles. It has two forms: Caput: When the most proximal cervical vertebrae (C1 or C2) are involved Collis: When any of the lower cervical vertebrae (C3 to C7) are involved The caput form (torticaput) involves muscles that move the skull or head joints; it is further described as anterocaput, laterocaput, or retrocaput. The collis form involves muscles that control the lower cervical vertebrae and is further described as anterocollis, laterocollis, retrocollis, or torticollis. These dystonias affect≥2 contiguous body parts. Meige syndrome(blepharospasm plus oromandibular dystonia) consists of involuntary blinking, jaw grinding, and grimacing, usually beginning during late adulthood. It must be distinguished from the buccal-lingual-facial chorea of tardive dyskinesia and tardive dystonia (a variant of tardive dyskinesia). 