Chairman’s Summary

Abstract

The syndrome of chronic normal pressure hydrocephalus (NPH) in the adult does not intuitively lead to easy explanation. If we consider the material presented in this session, there have been two salient notions. The first of these is the importance of intracranial pressure and pressure/volume relationships in the production of normal pressure hydrocephalus. These contributions argue that the normal pressure entity does not really exist and that in fact all hydrocephalus is at periods high pressure hydrocephalus, documented as periodic elevations of steady state ICP or as alterations of transient phenomena. The report of MAIRA and ROSSI (C:l) purports to provide evidence that ICP in the syndrome of NPH in fact undergoes abnormally high oscillations, and that such oscillations might play a role in the pathogenesis of the syndrome. Mean ICP was elevated during sleep, particularly REM sleep. Since REM sleep is a relatively short cycle this suggests not a change in fluid production or absorption but rather a change in the pressure/volume relationship and an increase during REM sleep of cerebral blood volume (CBV). Similar sleep cycle findings have been shown in patients with glaucoma.