The lateral roentgenogram of the neck; with comments on the atlanto-odontoid-basion relationship.

Abstract

The lateral cervical roentgenogram is a useful guide in evaluating the bony and soft-tissue relationships of the neck. In an effort to establish certain normal measurements in this area we reviewed 700 lateral cervical roentgenograms from the files of the Mayo Clinic, of which 600, technically adequate and without detectable abnormalities, were included in the study. The roentgenograms were taken with the patient sitting erect and with the neck in the neutral position. The target-to-film distance was 60 inches. Measurements were made from the films without correction for the minor error due to magnification. Regions Evaluated Retropharyngeal Space: In Figure 1 the retropharyngeal space is indicated by the letter A. For convenience, we chose to measure this from the antero-inferior aspect of the second cervical vertebra to the posterior wall of the pharynx. Retrotracheal Space: The retrotracheal space, represented in Figure 1 by the letter B, was measured from the anteroinferior aspect of the sixth cervical vertebra to the posterior aspect of the trachea. Although involvement of the retropharyngeal space by disease is well documented, involvement of the adjacent retrotracheal space is seldom described. Spinal Canal: Anteroposterior Diameter: Measurements on the spinal canal were made from the posterior aspect of the vertebrae to the nearest point on the corticated line at the fusion of the laminae and spinous processes of cervical vertebrae one, two, three, five, and seven. This region is indicated in Figure 1 by the letters C, D, E, F, and G. The Atlanto-Odontoid-Basion Relationship: The relationships of the tip of the odontoid process to the basion (anterior lip of the foramen magnum) and to the anterior arch of the atlas were studied. Esophageal Air: The presence or absence of air in the cervical portion of the esophagus was noted. The Retropharyngeal and Retrotracheal Spaces The normal values and variations for sagittal measurements of the retropharyngeal and retrotracheal spaces are listed in Table I. It is suggested that measurements for the retropharyngeal space greater than 7 mm. in both children and adults, and measurements of the retrotracheal space greater than 14 mm. in children and 22 mm. in adults, should warrant further investigation to exclude the possibility of a pathologic process.2 With reference to the retrotracheal space, we have noted that the contour of the posterior tracheal wall is not influenced by cervical hypertrophic ridging as may often be observed to occur in the barium-filled esophagus. Any localized irregularity of the posterior tracheal wall should be regarded as significant until proved otherwise. Such localized bulges may be due to benign or malignant neoplasms (primary or secondary), to hematomas, or to inflammation (Fig. 2, a, b, c).