✓ Subarachnoid hemorrhage (SAH) was produced experimentally by injecting normal dog's blood as well as reserpinized dog's blood into the chiasmal cistern of the dog. The following observations were made: 1) After SAH with normal dog's blood, the intima of the basal truncal arterial wall showed some or all of such ultrastructural changes as appearance of vacuoles and dense bodies in endothelial cells, detachment of endothelial cells, appearance of intimal cells, and intimal thickening. The changes first appeared 2 hours after SAH, culminated at 3 to 7 days after SAH, and persisted up to 1 month after SAH. 2) After SAH with normal dog's blood, the media of the basal truncal arterial wall showed some or all of such ultrastructural changes as moth-eaten contour of muscle cells, appearance of intracytoplasmic vacuoles and dense bodies, appearance of cell debris, enlargement of interstitial space, and appearance therein of dense particles. These findings, which, in short, are to be expressed as myonecrosis and its repairing process, first appeared 2 hours after SAH, culminated at 1 to 4 months after SAH, and persisted up to 1 year after SAH. 3) Three and 5 days following SAH with reserpinized dog's blood, ultrastructural findings of the intima and media of the basal truncal arterial wall were entirely normal.
On the basis of the above findings, it was concluded that the ultrastructural changes in the cerebral arterial wall observed after SAH with normal dog's blood occurred as a consequence of vasospasm. The possibility that late spasm, in turn, might be facilitated by myonecrosis, could not be denied.