✓ The size of the ventricular system and cerebrospinal fluid (CSF) flow were determined in 17 patients with plateau waves, using computerized tomography (CT) and isotope cisternography. Some patients had increased intracranial pressure (ICP) resulting from space-occupying lesions and other causes, and some had normal ICP observed in normal-pressure hydrocephalus. The size and shape of the ventricular system during plateau wave phases as ascertained by CT showed little or no change as compared with its size and shape during the interval phases between two waves. It was also noticed that, in patients with supratentorial masses, the midline shift showed no difference in degree between the two phases. These findings suggest that there is little change in the intracranial CSF volume between the two phases, that is, there is little compensatory outflow of the intracranial CSF for the ICP variations. These results may also support the assumption that the plateau waves are not caused by an intermittent obstruction of the CSF pathways. Isotope cisternography showed a marked delay of clearance of radioactivity from the intracranial CSF in 15 patients. The cisternographic pattern in patients with increased ICP and the absence of ventricular dilatation demonstrated an abnormally large accumulation of radioactivity over the cerebral convexities, and the pattern in patients with normal-pressure hydrocephalus showed complete obstruction of the subarachnoid space over both cerebral convexities. These observations suggest that, in patients with plateau waves, there is a marked delay in CSF absorption. The authors postulate that the reduction of CSF absorption may create a critically tight condition within the cranial cavity and act as a contributory factor in the development of the plateau waves.
Minoru Hayashi, Hidenori Kobayashi, Hiroyuki Fujii and Shinjiro Yamamoto
Minoru Hayashi, Shinobu Marukawa, Hiroyuki Fujii, Tetsuo Kitano, Hidenori Kobayashi and Shinjiro Yamamoto
✓ Simultaneous continuous recording of intracranial pressure (ICP) and systemic blood pressure was carried out in 26 patients admitted within 1 week after subarachnoid hemorrhage (SAH) due to a ruptured intracranial aneurysm. The patients were graded as described by Hunt and Hess. Recordings were made for 1 to 5 days. The more impaired the consciousness, the higher the rate of ICP. In Grade III, IV, and V patients, the mean ICP level was in the range of 15 to 40 mm Hg, 30 to 75 mm Hg, and exceeded 75 mm Hg, respectively. A definite correlation between vasospasm shown by cerebral arteriogram and the clinical grade was not observed. In our series of ICP recordings, we never observed a typical plateau wave. The variations of ICP seen in Grade III and IV patients were the B- and C-waves (15 to 45 mm Hg in amplitude) described by Lundberg, and those in Grade V patients were the high amplitude monotonous waves synchronous with the arterial pulses (15 to 40 mm Hg in amplitude). These phenomena may indicate that Grade III and IV patients with SAH are in a condition of cerebral vasomotor instability, and Grade V patients have cerebral vasomotor paralysis.