• Lyle J Dennis, Jan Claassen, Lawrence J Hirsch, Ronald G Emerson, E Sander Connolly, and Stephan A Mayer.
• Division of Critical Care Neurology, Department of Neurology, College of Physicians and Surgeons, Columbia University, 710 West 168th Street, New York, NY 10032, USA.
• Neurosurgery. 2002 Nov 1;51(5):1136-43; discussion 1144.

ObjectiveAlthough in-hospital seizures have been reported for 3 to 24% of patients with aneurysmal subarachnoid hemorrhage (SAH), nonconvulsive status epilepticus (NCSE) has not been previously described. We sought to determine the frequency and clinical features of NCSE among comatose patients with SAH.MethodsBetween November 1997 and February 2000, we performed continuous electroencephalographic (cEEG) monitoring for at least 24 hours for all patients with aneurysmal SAH who were treated in our neurological intensive care unit and exhibited unexplained coma or neurological deterioration. NCSE was diagnosed when cEEG monitoring demonstrated continuous or repetitive electrographic seizures exceeding 1 hour in duration. Refractory NCSE was treated aggressively with intravenous anticonvulsant administration and continuous-infusion midazolam therapy.ResultsOf 233 patients with SAH who survived the first 48 hours of hospitalization, 101 were stuporous or comatose at some point during their hospitalization. Twenty-six of those patients underwent cEEG monitoring, and eight were diagnosed as having NCSE, an average of 18 days (range, 5-38 d) after SAH. All eight patients were receiving prophylactic anticonvulsant therapy. Four patients were persistently comatose and four demonstrated deterioration to stupor or coma; only one exhibited overt tonicoclonic activity. A worst Hunt and Hess grade of IV or V, older age, ventricular drainage, and cerebral edema on computed tomographic scans were identified as risk factors for NCSE (all P < 0.01). NCSE was successfully terminated for five patients (63%), but only one experienced clinical improvement, which was transient; all eight patients eventually died after a period of prolonged coma.ConclusioncEEG monitoring detected NCSE for 8% of patients with SAH and otherwise unexplained coma or neurological deterioration. The seizures were highly refractory to therapy, and the prognosis for these patients was extremely poor. Routine postoperative cEEG monitoring of patients with SAH who are at high risk for NCSE, allowing earlier diagnosis and treatment, offers the best chance of improving the outcomes for patients with this disorder.

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