Successful selection of patients with intractable extratemporal epilepsy using non-invasive investigations

Patients with intractable epilepsy, operated for extratemporal epileptogenic foci, have often been found to have poorer surgical outcome compared with those with temporal lobe foci. The objective of this study is to assess the surgical outcome in patients with extratemporal foci, operated at the All India Institute of Medical Sciences (AIIMS), New Delhi.

Patients of intractable epilepsy with extratemporal foci on detailed investigation constituted the study group. They were evaluated by the 'Comprehensive Epilepsy Care Team' at the AIIMS with detailed clinical assessment, interictal EEGs, video-EEG studies, magnetic resonance imaging (MRI) with special sequences tailored for evaluation of the temporal lobes and for cortical dysplasias and single photon emission computerised tomography (SPECT) studies. Intraoperative electrocorticography was obtained in some patients. Outcome was assessed on follow-up, and graded according to Modified Engel's Grading System.

Twenty-five patients (18 males, 7 females) with a mean age of 19.7 years (age range 7-45 years) were operated and assessed during the study period, for surgical outcome with a mean follow-up of 16.8 months (range 3 months to 6.5 years). Twenty patients (87%) were found to have a good outcome (Modified Engel's grades I and II), while three had poor outcome, one died and one was lost to follow-up.

We found a good seizure outcome in patients who underwent resection of extratemporal epileptogenic foci, one of the reasons being presence of a lesion in all patients. Careful patient selection even with non-invasive investigations can aid in obtaining a good outcome in this group of patients.