Long-term Outcomes After Nonlesional Extratemporal Lobe Epilepsy Surgery

Abstract

Surgery for medically resistant epilepsy can be highly effective for patients with a focal epileptogenic lesion identified on a magnetic resonance imaging (MRI) scan.¹ When MRI fails to detect a potentially epileptogenic lesion, the chances of an excellent surgical outcome are significantly lower.^2-6 Surgical outcomes for patients with neocortical epilepsy who have normal preoperative MRI findings are particularly poor, which reflects the difficulty in localizing and resecting the epileptogenic zone. The reported rates of excellent surgical outcome for nonlesional partial epilepsy range from 41% to 65% for the temporal lobe,^2,7-9 37% for mixed mesial temporal and neocortical sites,¹⁰ and 29% to 56% for extratemporal epilepsy.^3,5,11-13 Reports of outcome in nonlesional extratemporal epilepsy, however, are from relatively small numbers of highly select patients³ with 1-year follow-up (17 patients in Smith et al,¹³ 26 patients in Mosewich et al,¹² 43 patients in Siegel et al,¹⁴ 43 patients in Dorward et al,¹⁵ 10 patients in Chapman et al,¹¹ 18 patients in Jeha et al,⁵ and 7 patients in Bien et al³). Except for Bein et al,³ none of these studies provide data on the total cohort of patients evaluated in order to arrive at the subset considered for resective surgery. In addition, these studies do not report the number of patients who underwent long-term intracranial electroencephalographic (EEG) monitoring but who were not candidates for resection. Thus, the outcomes after resective surgery are from a highly select group of patients, and they do not reflect the probability of an excellent outcome prior to intracranial EEG monitoring. This information would be very useful for counseling patients in the clinic.