Abstract
In spite of the emphasis on the clinical importance of plateau waves, the precise mechanism of the plateau waves is still obscure.
Continuous intracranial pressure recording is performed in patients with normal pressure hydrocephalus after rupture of an intracranial aneurysm and in a patient with a pontine hemorrhage. Recordings in these patients showed frequent acute transient rises of intracranial pressure resembling the plateau waves. These transient intracranial pressure elevations developed from a low basic level of intracranial pressure and the height of each waves usually ranged only between 20 and 40 mmHg, i.e., the waves seen in these patients were smaller than those seen with increased intracranial pressure from brain tumors. Nevertheless, they had characteristics of plateau waves.
The cerebral circulation was studied with carotid angiography and by the Xenon 133 clearance method. With the clearance method, a decrease in the cerebral blood flow was revealed in normal pressure hydrocephalus. A slow circulation time determined with angiography was shown in a pontine hemorrhage patient.
From such experience, we speculated the following possibility for development of the plateau waves. A marked reduction in cerebral circulation may produce hypoxic metabolites of the brain, and these in turn induce dilatation of cerebral vessels responsible for producing the plateau waves.
