Intracranial pressure (ICP) was recorded continuously in 24 pre-operative patients with angiographic evidence of diffuse cerebral vasospasm due to rupture of an intracranial aneurysm. Increased ICP in the range of 20-40 mmHg was observed in the acute stage after subarachnoid hemorrhage (SAH) in 12 out of 24 patients with no signs of angiographic evidence of diffuse vasospasm. While awaiting clinical improvement, the mean ICP began to decrease gradually to a level below 15 mmHg within a few days. Bilateral carotid angiography at this time showed diffuse vasospasm. Depressed and low ICP was observed in 10 of the patients with angiographic evidence of diffuse vasospasm, in whom the ICP recording was started between 6-11 days after SAH. Thus, 22 out of 24 patients showed low and depressed ICP in early phases of diffuse vasospasm.
On continuing the recording, however, a secondary increase of ICP followed in 14 patients always associated with serious neurological deterioration. The pressure curve of this group was characterized by a biphasic pattern, i. e., depressed ICP followed by increased ICP. We refer to this pressure pattern as “Diffuse Vasospasm Type I”.On the other hand, the remaining 8 patients had no increase of ICP throughout the course of diffuse vasospasm. The term “Diffuse Vasospasm Type II” has been used for this type of ICP tracing.
Of the 16 patients of Diffuse Vasospasm Type I, 7 patients were found to show enlargement of the ventricular system and 11 patients to have widespread low density on CT scan. On the other hand, 2 out of 8 patients of the Diffuse Vasospasm Type II were found to show a circumscribed low density on CT scan.
The changes in cerebral blood flow (CBF) were analyzed. Mean value of CBF of 47.6 ml/100 gr/min has been obtained in patients with no cerebral vasospasm. Type I and II patients of low ICP phase showed flows of 35.4 and 36.2 ml/100 gr/min, respectively. Marked reduction in CBF of 25.2 ml/100 gr/min was found in Type I patients of high ICP phase. It is suggested that a level of below 25 ml/100 gr/min may lead to major neurological deterioration.
