Compression of the outlets of the leptomeningeal veins--the cause of intracranial plateau waves.

The hypothesis is developed that plateau waves (PW) are caused by an abrupt elevation of postcapillary flow resistance induced by compression of the outlets of the leptomeningeal veins. It is shown by means of a physical model that the main prerequisite for venous outlet compression consists in an elevation of the outflow resistance of the cerebrospinal fluid. Resolution of PW is demonstrated to be brought about by expulsion of fluid from the cranial vault during the plateau phase, thus allowing the outlets of the leptomeningeal veins to re-open. Brain shifting seems also to participate in this redistribution of the intracranial space in favour of the vasculature. It is further proven that PW may occur in rats with chronically or acutely increased CSF outflow resistance. PW triggering was investigated in these animals. All phenomena known to be related to PW are explained by the concept developed.