Plateau-wave phenomenon (I). Correlation between the appearance of plateau waves and CSF circulation in patients with intracranial hypertension.

Plateau waves, as described by Lundberg (1960), can often be observed in patients with increased intracranial pressure (ICP) resulting from brain tumours, benign intracranial hypertension and other causes. The clinical significance of the waves, however, is still debated. In this study, the ICP was recorded continuously, the size of the ventricular system was evaluated using computerized tomography (CT), the cerebrospinal fluid (CSF) flow was studied using isotope cisternography, and the absorptive capacity of the CSF was determined by measuring the conductance to CSF outflow, in 94 patients with increased ICP. All patients who received continuous ICP monitorings had a basic ICP level of more than 200 mmHg, and these patients were assigned to two groups on the basis of the presence or absence of the plateau waves in the ICP recordings: group I comprising 17 patients without plateau waves but with a high ICP resulting from subarachnoid haemorrhage or hypertensive intracerebral haemorrhage, within 5 days after the start of bleeding; and group II consisting of 77 patients with both plateau waves and a high ICP resulting from brain tumours, meningitis carcinomatosa, benign intracranial hypertension, superior sagittal sinus thrombosis and communicating hydrocephalus. The isotope cisternography and conductance to CSF outflow studies showed that there was neither a delay in CSF circulation nor an impairment of CSF absorption in the group 1 patients and these patients showed no ventricular dilatation on CT, whereas there was a marked sluggishness in the CSF flow and a severe defect in the CSF absorption capacities of the group II patients irrespective of the presence or absence of ventricular dilatation on CT. The present observations indicate that patients with a plateau-wave phenomenon have a marked impairment of CSF absorption and CSF flow. We suggest that the phenomenon is an important sign indicating an impairment of CSF absorption capacities.