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.
Two patients with arteriovenous malformation were studied by position emission tomography, using the steady-state technique with 15O2. In the first patient, who had seizures, preceded by auditory hallucinations, an area of decreased cerebral blood flow and oxygen consumption was shown just behind the malformation. In the second patient, who had repeated attacks of right hemiparesis, an area of decreased blood flow and oxygen metabolism was shown at distance of the malformation. These areas of low flow and metabolism are most probably the result of a vascular steal phenomenon and the origin of the transient neurological symptoms in both patients.
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