Fig. 4.

In the presence of diffuse vasospasm affecting both the ICA and MCA, there are decreases in the blood flow in the MCA, and hypertension, whilst causing a slight increase in the flow supply, is unable to restore it to normal. The largest flow reduction is observed in cases involving long segment disease of the worst severity and in the case of an incomplete CoW. In the presence of a complete CoW, the flow is related principally to the vasospasm within the MCA, being less sensitive to the vasospasm occurring in the ICA. CoW, circle of Willis; d, distributed spasm; Hype, hypertension; ICA, internal carotid artery; L, left vessel; MCA, middle cerebral artery.