Assessment of cerebral blood flow by its frequency distribution in cerebral vascular diseases

Cerebral blood flow (CBF) was measured by the stable xenon inhalation method, and the frequency distribution of flow levels analysed in patients with intracerebral haemorrhage, subarachnoid haemorrhage (SAH), vascular disease involving major arteries, lacunar infarction and normal subjects. The frequency distribution was skewed towards lower CBF values, and the mode, at which the frequency of values was highest, was lower than the mean CBF. Furthermore, the frequency at the mode was higher when mean CBF was low. Since many areas of the brain had lower flow than the mean CBF, it is suggested that attention must be paid to local flow levels as well as the overall mean value. A small decrease in mean CBF may mean the development of significant ischaemia in many regions.