Factors leading to hydrocephalus after aneurysmal subarachnoid hemorrhage

The predisposing factors for the development of posthemorrhagic hydrocephalus, requiring shunt implantation, after subarachnoid hemorrhage (SAH) are still not exactly known. Therefore we analyzed the patients with SAH, who were treated in our department with respect to the development of chronical cerebro-spinal fluid (CSF) imbalance, trying to define predictive parameters for this entity.

All patients presenting with SAH were analyzed retrospectively between September 1992 and July 1998. Special consideration was given to the initial CT scan (cistern index, Fisher grade, bicaudate index) and the requirement for an external ventricular drainage. Other possible predictive factors as age, Hunt & Hess grade, electrolyte disturbances and operative techniques were also evaluated.

During the investigation period, 283 patients presenting with aneurysmal SAH underwent surgery. Fifty-two patients (18.4%) required a shunting procedure due to chronic posthemorrhagic hydrocephalus. The mean time interval between the initial bleeding and shunting was 28 days. All of these patients required a significantly longer external CSF drainage (p < 0.001) with a much higher amount of daily drained CSF (p < 0.001). The evaluation of the initial CT scan revealed no correlation between the amount of blood and later shunt dependency. However, there was a significant correlation with the bicaudate index (p < 0.01).

Chronic hydrocephalus after aneurysmal SAH is an important complication. The recovery-time of shunt dependent patients is definitely prolonged compared to non-shunted patients. Predictive factors of shunt dependency seem to be length and amount of the external CSF drainage, as well as a high bicaudate index.