Pathology of Myonecrosis following Cerebral Vasospasm

Histological changes of the cerebral arteries taken from 3 patients who died of cerebral vasospasm after subarachnoid hemorrhage were investigated and compared with those of 10 dogs with experimental vasospasm induced by a subarachnoid injection of 0.15-0.20 mgkg of epinephrine. The cerebral arteries of the human autopsy cases known to have undergone spasm exhibited a wide lumen with thin media resulting from necrosis of the smooth muscle cells. These necrotic smooth muscle cells were replaced by scattered, eosinophilic cellular debris, especially in the outer layer of the media. In the experimental study, the subarachnoid injection of epinephrine produced frank necrosis of the smooth muscle cells and marked dilatation of the arterial lumen, especially in 5 dogs, and was associated with hypothalamic infarctions and inflammatory swellings of small subarachnoid arteries. Dogs sacrificed artificially revealed myonecrotic changes that were uniformly and intensely stained with eosin, whereas those of spontaneous death revealed myonecrosis similar to human autopsy cases. It is suggested that myonecrosis might be formed as a result of prolonged, intense contraction induced by epinephrine as well as by vasoactive exudates from the hypothalamic lesions or the small subarachnoid arteries.