Montreal Neurological Institute and Hospital, and the Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
Objectives: The aim of this study is to characterize the clinical features and prognostic factors for intractable, post-encephalitic epilepsy.
Methods: We studied retrospectively 42 patients (26 men) evaluated between 1982 and 1999. MRI, neuropsychological findings, interictal and ictal scalp EEG were reviewed for all patients. Fifteen patients had additional stereo EEG (SEEG) studies.
Results: The mean age at encephalitis was 17 years (SD = 15.5); etiology was identified in 18 patients. During the acute illness, 79% had status epilepticus (SE) or recurrent seizures and 76% were in coma; mean Glasgow outcome scale (GOS) was 3.6 (SD = 0.8). The mean latency to seizure onset was 0.8 years (SD = 1.9). The majority (72%) presented with complex partial seizures with or without secondary generalization. According to interictal epileptiform findings and the predominant seizure onset pattern as found on scalp EEG, patients were unilateral temporal (UTLE) = 8, bilateral temporal (BTLE) = 12, and extratemporal/multifocal or generalized (ETMFE) =
22 patients. MRI atrophy and/or signal changes were unilateral temporal in 7 (18%), bilateral temporal in 5 (13%), multilobar/diffuse in 20 (51%), and absent in 7 (18%). ANOVA revealed significant differences in mean GOS between UTLE versus BTLE and ETMFE (4.7 versus 3.2 versus 3.6; p < 0.0001), but not in age at encephalitis. Latency to the first unprovoked seizure was shorter in patients with ETMFE compared to UTLE and BTLE (p < 0.01). Surgery was performed in 24 patients. The best outcome was obtained in UTLE (7/8 class I and II). In the others, outcome was poor in the majority (13/16 class III and IV).
Conclusion: There is a small subgroup of patients with postencephalitic UTLE for whom the outcome is favorable. The majority of our patients had multifocal seizure onset with BTLE and ETMFE, and poor outcome after surgical treatment.