[Deviation and rotation of the larynx in computer tomography]

Many authors described the clinical importance of asymmetry of the laryngeal framework. However, its pathogenesis is generally unknown. In this study, CT images of 315 Japanese subjects were investigated to define the laryngeal position relative to the midline of the cervical vertebra. The CT slice of each subject within 5 mm cephalad of the cricoarytenoid joint was traced. Then, the deviation and rotation angles were measured using our method. Seventy one percent of the subjects' larynges deviated and/or rotated to the right side, while 17% to the left side. Six percent showed neither deviation nor rotation. As to the rest of 6%, deviation and rotation were in opposite directions. Besides, the length of the thyroid alae were measured in 282 subjects. Left ala was longer in 55%, and right was in 23%, and almost equal in 22%. The conclusions are as follows, 1. The majority of the subjects' CT images showed deviation and/or rotation of the laryngeal framework to the right side. 2. So called idiopathic laryngeal deviation is a case which observed in those cases with remarkable deviation and/or rotation of the laryngeal framework. 3. Aging seemed to be an important factor in acceleration of the laryngeal deviation and rotation. 4. The type of diseases and the side of mass lesions had no statistical significance in deviation and rotation of the larynx.