External ventricular drainage response in poor grade aneurysmal subarachnoid hemorrhage: effect on preoperative grading and prognosis.

Introduction: The importance of preoperative response to external ventricular drainage (EVD) for treatment of acute hydrocephalus (HCP) following poor grade (Hunt & Hess grade IV or V) aneurysmal subarachnoid hemorrhage (aSAH) has not been clearly defined. The effect of EVD response on preoperative grade and prognosis is described.

Methods: Fifty-nine poor grade patients had an EVD placed preoperatively and underwent definitive aneurysm treatment between September 1996 and March 2002. Patients improving > or = one Hunt and Hess grade were considered responders. Case-control comparisons were completed for each responder, based on clinical grade; the pre-EVD grade and the post-EVD (response) grade were used to generate two independent control cohorts. Logistic regression was used to evaluate the relationship of 12-month modified Rankin disability score (mRS) to clinical grade.

Results: Nineteen (32%) responders were identified, and were less likely Grade V (p < 0.05), and more often had smaller (<13 mm, p < 0.01) and posterior circulation (p < 0.03) aneurysms. The frequency of favorable outcome (mRS < or= 3) was greater in responders than non-responders (68% vs. 28%, p < 0.001). Responders had a similar incidence of favorable outcome as response-grade controls (74%), and a higher incidence of favorable outcome than pre-EVD controls (47%). Regression analysis identified the post-EVD grade, but not the pre-EVD grade, as significantly predictive of long-term outcome (p < 0.04).

Conclusion: Long-term outcomes in poor grade patients who improve after EVD placement are similar to patients with lower grade hemorrhages. When an EVD is placed preoperatively in a poor grade aSAH patient, the neurological status after EVD determines the clinical grade.