Ictal EEG wave forms from epidural electrodes predictive of seizure control after temporal lobectomy.

Ictal wave form characteristics--frequency, spatial distribution, and duration--were analyzed for 140 complex partial seizures recorded from epidural strip electrodes implanted in 28 patients. None had abnormalities on imaging studies. All had bilateral electrode placements, unilateral seizure onsets, temporal lobectomies, and were followed for a mean of 33 months postoperatively. Sixteen patients (57%) became free of complex partial seizures: 12 had reductions in seizure frequency of at least 50% but were not seizure-free. The only predictor of the seizure-free state was the presence of low voltage fast activity (LVF), in the alpha or beta ranges, localized to one gyrus. This phenomenon occurred in 14/16 seizure-free patients, 2/12 of others (P < 0.001). As seizures progressed, LVF typically increased in amplitude, propagated, and slowed into the theta range. Wave forms were classified into 8 categories based upon their frequency and morphology. Stepwise discriminant analysis of these wave forms, with consideration of whether they were localized or regional, revealed that both frequency and localization were critical for the post-surgical prognosis. The mere presence of a localized seizure onset was unreliable unless the wave form was taken into account. Well-localized rhythmic activity over 8 Hz at seizure onset from epidural subtemporal electrodes predicts surgical success. Slower rhythms imply greater separation in space and time from seizure onset.

[1]  M R Sperling,et al.  Comparison of depth and subdural electrodes in recording temporal lobe seizures , 1989, Neurology.

[2]  H. Jasper,et al.  EEG and cortical electrograms in patients with temporal lobe seizures. , 1951, A.M.A. archives of neurology and psychiatry.

[3]  E. Gibbs,et al.  Epilepsy: a paroxysmal cerebral dysrhythmia , 1937, Epilepsy & Behavior.

[4]  K D Laxer,et al.  Subdural electrodes for seizure focus localization. , 1986, Neurosurgery.

[5]  Klass Dw Electroencephalographic manifestations of complex partial seizures. , 1975 .

[6]  R. Flink,et al.  Interictal and ictal activity recorded with subdural electrodes during preoperative evaluation for surgical treatment of epilepsy , 1989 .

[7]  P Gloor,et al.  Contributions of electroencephalography and electrocorticography to the neurosurgical treatment of the epilepsies. , 1975, Advances in neurology.

[8]  P. Crandall,et al.  Surface and Deep EEG Correlates of Surgical Outcome in Temporal Lobe Epilepsy , 1981, Epilepsia.

[9]  A. Delgado-Escueta Epileptogenic paroxysms , 1979, Neurology.

[10]  S. Goldring,et al.  Surgical management of epilepsy using epidural recordings to localize the seizure focus. Review of 100 cases. , 1984, Journal of neurosurgery.

[11]  T. Babb,et al.  A Comparison of EEG Seizure Patterns Recorded with Surface and Depth Electrodes in Patients with Temporal Lobe Epilepsy , 1976, Epilepsia.

[12]  R. Walter Tactical Considerations Leading to Surgical Treatment of Limbic Epilepsy , 1973 .

[13]  G. Ojemann,et al.  Multidisciplinary prediction of seizure relief from cortical resection surgery , 1986, Annals of neurology.

[14]  S. Spencer,et al.  Combined depth and subdural electrode investigation in uncontrolled epilepsy , 1990, Neurology.

[15]  G. Walker,et al.  Chronic subdural strip electrode recordings for difficult epileptic problems , 1988 .