The posterior crico-arytenoid muscle in two cases of Shy-Drager syndrome with laryngeal stridor. Comparison of the histological, histochemical and biometric findings.

The histological, histochemical and biometric findings in the posterior crico-arytenoid muscle in two patients with Shy-Drager syndrome were compared with those found in cases of carcinoma of the larynx. In biopsy specimens from the patients with laryngeal carcinoma, neurogenic atrophy and various structural changes in the muscle fibres were the prominent features. In the two patients with Shy-Drager syndrome these changes were not present and the only significant finding was the more pronounced type I fibre atrophy, with type II fibre predominance in the more severely affected case. These findings do not permit the vocal cord paralysis seen in the Shy-Drager syndrome to be explained by motorneuron loss and denervation. It is postulated that a possible cause may be a biochemical defect in the brain.