Intracranial pressure in the normal monkey while awake and asleep

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Abstract
Intracranial pressure (ICP) was recorded continuously by telemetry in 7 normal monkeys trained to eat, sleep, and live in a primate chair. EEG, electromyography and blood pressure were also measured by conventional means. During wakefulness and all stages of sleep except desynchronized sleep, the ICP record showed small short-term variations in pressure. During desynchronized sleep, the mean ICP rose on the average to 170 .+-. 6 mm H2O above the ICP levels in the other states of sleep, and the pulsation pressure variation increased by a factor of 3. The episodes occurred 10 .+-. 12 times during the night and lasted for 6.8 .+-. 1.4 min, during which the average systemic blood pressure decreased by 19 .+-. 1.6 mm Hg. These ICP waves occurring during desynchronized sleep resemble the plateau waves described by Lundberg, but are of smaller magnitude and they appear to be a normal characteristics of sleep in the macaque monkey. Bilateral sympathectomy of the superior cervical ganglia in 4 of the monkeys did not alter significantly the duration, amplitude, or frequency of occurrence of the ICP waves during desynchronized sleep.