Extratemporal surface EEG features do not preclude successful surgical outcomes in drug‐resistant epilepsy patients with unitemporal MRI lesions

Abstract

Of 47 patients with onset of intractable partial seizures and temporal lobe MRI lesions, subjected to presurgical evaluation and temporal lobe surgery, we identified eight (mean age: 24 years; range: 7-52 years) demonstrating surface interictal and/or ictal EEG features suggestive of an extratemporal localisation. All eight patients underwent surgery aiming to predominantly resect the lesion, without extending to the extratemporal region. The patients were prospectively followed (mean follow-up duration: 38 months; range: 12-66 months) and all achieved excellent postoperative seizure control. Extratemporal surface interictal/ictal EEG features were more often encountered in tumoural and focal cortical dysplasia cases, compared with medial temporal sclerosis cases, and were most frequently localised over frontopolar and suprasylvian-pericentral locations. We postulate that propagation of interictal/ictal activity from the epileptogenic region of the temporal lobe to extratemporal neocortical areas, perhaps utilising the temporal pole and insula as intermediary nodes of a common epileptogenic network, accounts for the presence of our cohort's discordant lesion and EEG features.