Temporal Lobectomy for Refractory Epilepsy in the U.S. Military

Military Medicine, Mar 2005 by Erickson, Jay C, Ellenbogen, Richard G, Khajevi, Kaveh, Mulligan, Lisa, Et al

Objectives: To determine the characteristics, seizure outcomes, and quality-of-life outcomes for military beneficiaries undergoing partial temporal lobectomy for refractory epilepsy at the only U.S. military medical center with a comprehensive epilepsy surgery program. Methods: The records of all 84 patients treated with partial temporal lobectomy between 1986 and 2000 at Walter Reed Army Medical Center were retrospectively reviewed. Outcome measures included seizure frequency according to the Engel classification system, driving, employment, anticonvulsant use, and military service. Results: The study cohort consisted of 72 military dependents, 10 active duty military members, and 2 military retirees. Two years after surgery, 65 (92%) of 71 patients had seizure improvement (Engel classes I-III) and 46 (66%) of 71 had seizure remission (Engel class I). Driving and employment rates increased after surgery, whereas anticonvulsant use decreased. Five (50%) of 10 active duty patients achieved seizure remission postoperatively and continued to serve in the Armed Forces. Active duty patients had a later age of seizure onset, shorter duration of epilepsy, and greater proportion of lesional epilepsy, compared with nonactive duty patients. Conclusions: Epilepsy surgery outcomes in the U.S. military are similar to those reported from nonmilitary centers, with the majority of patients experiencing seizure remission and improvements in quality-of-life measures. Complete seizure remission after successful anterior temporal lobectomy enables some active duty military members to continue service in the U.S. Armed Forces.

Introduction

Anterior temporal lobectomy is an established treatment for refractory temporal lobe seizures, the most common type of intractable epilepsy among adults, with approximately 50 to 70% of patients being rendered seizure-free by this procedure,1-5 A recent controlled trial of surgical treatment versus medical treatment for refractory temporal lobe epilepsy demonstrated the superiority of surgery, with 58% of patients being seizure-free 1 year after surgery compared with only 8% of patients who received medication alone.4 Improvements in quality-of-life measures after temporal lobectomy have also been reported.1,5-7

Epilepsy surgery outcomes have not been described for a military population. We report the characteristics, seizure outcomes, quality-of-life outcomes, pathological findings, and prognostic factors for patients undergoing partial temporal lobectomy for refractory temporal lobe epilepsy in a major U.S. military hospital. The findings are discussed in terms of their implications for the management of intractable epilepsy among military members.

Methods

Patients

Walter Reed Army Medical Center has been designated by the U.S. Department of Defense as the Center of Excellence within the military health care system for epilepsy surgery. It is currently the only U.S. military medical center with a comprehensive epilepsy surgery program. Between 1986 and 2000, 84 patients underwent epilepsy surgery on the temporal lobe at this center. All patients had complex-partial seizures, with or without secondarily generalized seizures, refractory to at least two medications. Seizures were present for at least 1 year and occurred more than once per month. All patients were determined to have seizures arising from a single temporal lobe based on an extensive preoperative evaluation (described below).

Preoperative Evaluation

All patients underwent a standard preoperative evaluation consisting of a comprehensive history and neurological examination, interictal scalp electroencephalography (EEG), videoEEC monitoring with surface electrodes, neuropsychological testing, intracarotid amobarbital testing (Wada), and brain imaging. Brain magnetic resonance imaging (MRI) was performed for 80 patients. Brain computed tomography (CT) was performed for four patients who were evaluated before MRI availability. Fifteen of 18 patients without evident abnormalities on brain MRI scans also underwent an interictal/ictal single-photon emission CT study using hexamethylpropyleneamine oxime. Subdural recording was performed for 37 patients with lateralizing but poorly localizing surface EEG monitoring results. The subdural recording covered the lateral frontal cortex and lateral, medial, and inferior temporal cortex. When surgery was to be performed on the language-dominant side, the language cortex was mapped either with cortical stimulation of the awake patient in the operating room or, more often, with subdurally implanted grid electrodes on the ward with video-EEG recording. Informed consent was obtained for all invasive procedures.

Surgery

Epilepsy surgeons (R.G.E., K.K., L.M.) assigned to Walter Reed Army Medical Center performed the surgery. Piecemeal resections were performed for the majority of patients. Seven patients had en bloc resections. Intraoperative electrocorticography was used for more than one-half of the patients, especially in earlier cases. The procedure in the majority of cases was standard anterior temporal lobectomy and included medial temporal structures. The margins extended posteriorly 3.5 to 4 cm in dominant lobe resections and 5 to 6 cm in nondominant lobe resections. Eight patients had selective amygdalohippocampectomy.