Effect of subarachnoid haemorrhage on micro-circulation in hypothalamus and brain stem of dogs.

In order to investigate the relationship between cerebral vasospasm and microvasculature in the hypothalamus and brain stem, colloidal carbon was infused into the vertebral artery at various time intervals after experimental subarachnoid haemorrhage in dogs. Experiments which demonstrated vasospasm on angiogram were always accompanied by ischaemic changes in serial sections taken from the anterior hypothalamus to the brain stem. However, when it was demonstrated by angiography that the vasospasm had disappeared, the micro-circulation was restored to normal. Electron microscopy of the hypothalamus 48 hours and one week after subarachnoid haemorrhage, demonstrated swelling of the endothelial cells, enlargement of the perivascular glia and increase in number of the pinocytic vesicles in the cytoplasm, thus showing vasogenic oedema in this area. It is assumed that in addition to the vasogenic substance in extravasated blood, changes in irritability of cerebral vessels through the vasomotor pathways in the hypothalamus and brain stem might play an important role in the production of cerebral vasospasm.