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The normal pediatric larynx on CT and MR.

PURPOSE
To determine the MR and CT appearance of the normal pediatric larynx.


METHODS
Fifteen CT scans and 15 MR examinations of children with normal larynges and airways were reviewed retrospectively. Characteristics that were noted included the level of the hyoid bone, calcification and signal intensity within separate laryngeal components, amount of paraglottic fat, anteroposterior airway diameters, and airway contours. Two cadaveric larynges were imaged by CT and MR and were then sectioned at corresponding levels and section thicknesses.


RESULTS
The larynx is higher in children than in adults, with the hyoid bone found at the C2-3 level in the youngest children (newborn to 2 years). The subglottic airway was narrowest in the youngest children. The hyoid bone was the only laryngeal structure ossified in any of the children. A thin line of high density was seen in the expected location of the thyroid cartilage in some children. The featureless circumferential soft tissue seen around the airway represented the uncalcified laryngeal cartilaginous structures. This was confirmed on gross sectioning of cadaveric larynges. The supraglottic airway contour was triangular or oval, the glottis was shaped like a teardrop, and the subglottic contour was oval. Contours were confirmed on histologic examination of necropsy specimens.


CONCLUSIONS
This preliminary study suggests that the pediatric larynx differs from the adult larynx with respect to size, position, consistency, and shape, and these differences are reflected on CT and MR studies.