Electroencephalographic Changes During Pressure Waves of ICP Following Experimental Subarachnoid Hemorrhage

Continuous recording of intracranial pressure (ICP) in an acute stage in patients with subarachnoid hemorrhage shows that the intracranial pressure has a marked tendency to rapid variations (pressure waves) superimposed upon an elevated basal pressure (Hayashi et al., 1977). A similar phenomenon can be produced in dogs by the infusion of blood into the subarachnoid space (Yamamoto et al., 1972). The pressure waves seen during increased ICP following subarachnoid hemorrhage appear to be produced by cerebral vasomotor instability due to brain stem dysfunction. The present investi gation was designed to clarify the exact source within the brain stem of the pressure waves, by examining changes in EEG during pressure waves following experimentally induced subarachnoid hemorrhage in dogs.