REMOTE SUBARACHNOID HEMORRHAGE IN THE POSTERIOR-FOSSA FOLLOWING SUPRATENTORIAL SURGERY - CLINICAL OBSERVATION OF 6 CASES

Haemorrhage in regions remote from the site of following intracranial operations is rare, but they do occur. We performed supratentorial cra niotomy on 639 patients between the time of introduction of computed t omography (CT) for clinical use in 1983 and June 1992; subarachnoid ha emorrhage (SAH) in the posterior fossa occurred postoperatively in six of these cases. These included four patients with tumours in the sell ar region, one with an arteriovenous malformation (AVM) and one who un derwent superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis. The ages of the six patients ranged from 17-72 years. Ha emorrhage occurred on the day of operation in one case and was detecte d on CT examination on the day following surgery in the remaining five cases. Of three patients with disturbance of consciousness, two under went suboccipital craniectomy for reduction of intracranial pressure, while one received barbiturate therapy and later underwent cerebrospin al fluid (CSF) shunt surgery. No special treatment was necessary for t he remaining three patients with less serious lesions. Five of the six patients ultimately recovered their pre-operative neurological status apart from the primary diseases. Factors inducing such haemorrhages s eem likely to include displacement of the cerebellum by reduced CSF pr essure during and after operations, and stretching and tearing of the veins and venules in the sulci of the tentorial surface of the cerebel lum. Consideration should therefore be given to the maintenance of an appropriate CSF pressure during operation; this is particularly import ant in elderly patients and those with an atrophied cerebral cortex.