Malignant hyperthermia in a family. The neurophysiological and light microscopical study of muscle biopsies of healthy members.

12 healthy persons--close relatives to two children who died of malignant hyperthermia--volunteered for biopsies of striated muscle and skin, electromyography and electroencephalography. The investigations of muscle biopsies comprised material for enzyme histochemistry and ordinary light microscopy including visualization of the intramuscular nerves. Out of 12 clinically healthy persons 9 revealed abnormalities of the muscle fibres, 11 showed degenerative and regenerative alterations in the intramuscular nerves, in EMG 7 turned out to produce slight neuropathy, and 7 displayed abnormal EEG tracings. These findings support the idea that the etiological key (or keys) in the peculiar pathophysiological entity of malignant hyperthermia may even be found outside the striated muscle cell.