Influence of unilateral vocal fold fixation on the structure of the intrinsic laryngeal muscles.

Histomorphometric data (fiber frequencies, fiber diameters, and atrophy factors) were determined in laryngeal muscles [thyroarytenoid (VOC), posterior (PCA) and lateral (LCA) cricoarytenoids, and cricothyroid (CT) muscles]. Seventy-three muscles (43,700 fibers) from normal and carcinoma-infiltrated sides of the larynges of 11 patients were analyzed. The fiber diameters showed uniform values of 24.2 +/- 9.1 microns. Type-I fibers were more frequent in the PCA and less frequent in the LCA and the CT. In the VOC, the ratio was 1:1. The unilateral fixation of a vocal fold modified the structures of the LCA and the CT. The VOC and the PCA were not affected. A hypothesis based on the phonatory function of the CT is used to explain its atrophy.