I. Neurosurg. / Volume 31 / September, 1969 Regional Cerebral Blood Volume During Acute Transient Rises of the Intracranial Pressure (Plateau Waves)* JARL RISBERG, PH.D., NILS LUNDBERG, M.D., AND DAVID H. INGVAR, M.D. Departments of Clinical Neurophysiology and Neurosurgery, University Hospital, Lund, Sweden I T is a well-known fact that progressive intracranial hypertension during one stage of its development is characterized by intermittent, sometimes paroxysmal symptoms. Continuous recording of the ven- tricular fluid pressure (VFP) in patients with expanding intracranial lesions has shown that such intermittent symptoms coin- cide with acute temporary rises of the VFP level? 8 The corresponding VFP curve usu- ally follows a specific pattern, characterized by a steep rise to a high level (60-100 mm Hg) and, following some minutes, an often equally steep fall. This gives the curve a pla- teau-like appearance (Figs. 1-3). The plateau waves have been subjected to extensive clinical studies? ~,13,~s-21 Variations of the VFP curve similar to plateau waves could be provoked by increasing the pres- sure in the ventricles at ventriculography or by exerting pressure on the region of a skull defect. It was inferred that an induced or spontaneous increase of the intracranial pres- sure may cause dilatation of cerebral vessels which in turn causes the intracranial pres- sure to rise further? s By means of simul- taneous recording of the cerebral blood flow~7 and the ventricular fluid pressure combined with cerebral angiography, it was shown that the plateau waves are accompanied by dilata- tion of cerebral arteries and, at the same time, a decrease of the cerebral blood flow? 9 These findings indicate that during the plateau waves there is an increase of the intracranial blood volume. In general, the studies quoted suggest that the plateau waves may appear indepen- Received for publication December 6, 1968. * A preliminary report of this paper was pre- sented at the meeting of the Scandinavian Neuro- surgical Society, Upsala, Sweden, September 1-2, 1967. This study was supported by the Swedish Medical Research Council (projects No. 21X-84-01 and 21X-84-02) and by the Wallenberg Founda- tion, Stockholm. dently of systemic circulatory events and that they are related to cerebral vasomotor changes and to a failure of mechanisms com- pensating intracranial volume and pressure variations. The observation of Langfitt and his group 1~,15 in animal experiments should be recalled in this connection. They produced a rise in intracranial pressure by expanding a subdural balloon. This initial rise was fol- lowed by a "secondary rise" which these in- vestigators ascribed to a reactive dilatation of cerebral vessels. In the present investigation we have mea- sured the regional cerebral blood volume (rCBV) in patients with plateau waves. The rCBV measurements have been carried out by means of a new, continuous, and rela- tively atraumatic method. 24,26 Since this method is continuous, it has been possible to record the intracranial pressure simulta- neously and to compare the VFP and rCBV events in detail. It will be shown that rCBV augmentations always took place during the plateau waves. Furthermore, the tracings we obtained show that the interrelations of the VFP and rCBV followed a well-defined pat- tern, with maximal blood volume values dur- ing the minutes preceding the rapid fall of the intracranial pressure at the end of the plateau wave. Material The rCBV was measured in two patients in whom the VFP was continuously re- corded for other purposes consistent with es- tablished principles practised in our neuro- surgical department, is Case 1. Intracranial Hypertension of Un- known Origin. A 42-year-old woman had a history of legal abortion because of rubeola, following which she complained of impaired 303