Epilepsy with temporal encephalocele: Characteristics of electrocorticography and surgical outcome

Abstract

Temporal lobe encephaloceles (TEs) are increasingly identified in patients with epilepsy due to advances in neuroimaging. Select patients become seizure-free with lesionectomy. In practice, however, many of these patients will undergo standard anterior temporal lobectomy. Herein we report on the first series of patients with refractory temporal lobe epilepsy (TLE) with encephalocele to undergo chronic or intraoperative electrocorticography (ECoG) in order to characterize the putative epileptogenic nature of these lesions and help guide surgical planning. This retrospective study includes nine adult patients with magnetic resonance imaging/computed tomography (MRI/CT)-defined temporal encephalocele treated between 2007 and 2014 at University of California San Francisco (UCSF). Clinical features, ECoG, imaging, and surgical outcomes are reviewed. Six patients underwent resective epilepsy surgery. Each case demonstrated abnormal epileptiform discharges around the cortical area of the encephalocele. Two underwent tailored lesionectomy and four underwent lesionectomy plus anterior medial temporal resection. Postoperatively, five patients, including both with lesionectomy only, had Engel class Ia surgical outcome, and one had a class IIb surgical outcome. The role of TE in the pathogenesis of epilepsy is uncertain. ECoG can confirm the presence of interictal epileptiform discharges and seizures arising from these lesions. Patients overall had a very good surgical prognosis, even with selective surgical approaches.

Small temporal pole encephalocele: A hidden cause of “normal” MRI temporal lobe epilepsy

“…This study emphasize, along with other two new studies, 13,14 the recent interest in small temporal encephaloceles as a significant cause of temporal lobe epilepsy in patients in whom MRI was read as normal or noninformative. In contrast with previous studies, [5][6][7][8][9][10][11][12][13][14] we have focused our study in patients with encephaloceles that are located at the tip of the temporal pole. Therefore, we were able to gather a homogenous cohort that potentially shared similar features, Semantic tests results are shown for a selected group of patients (n = 12) and for a group of control healthy subjects (n = 17).…”

“…In addition to other studies, [5][6][7][8][9][10][11][12][13][14] which mainly described the epilepsy found in patients with RFE, we also included patients with well-controlled epilepsy. In doing so we broaden the clinical spectrum associated to this type of lesion.…”

“…In this regard, small case-series [5][6][7][8][9][10][11][12] have previously emphasized that small temporal encephalocele could be an unrecognized cause of epilepsy. Two recent articles, 13,14 studying larger groups of patients, have provided further evidence about this pathology as a significant cause of temporal lobe epilepsy in patients in whom the MRI was read as normal or noninformative. However, all these previous studies have focused only on the description of epilepsy found in a select group of patients with refractory epilepsy, while they have not analyzed whether there are patients with a less severe phenotype.…”

“…We therefore could gathered a more homogenous group of patients that could faciltate the identification of characteristic features. We hypothesized that the localization of these lesions in the vicinity of the basal temporal language area, [14][15][16] when seated in the dominant temporal lobe, might contribute to distinct interictal and ictal manifestations, not previously highlighted, allowing for its differentiation from other focal epilepsies. Finally, to establish the relevance of small temporal pole encephalocele (STPE) in patients with focal epilepsy evaluated for surgery, we studied the frequency of this type of lesion within a large group of patients with different types of focal epilepsies refractory to antiepileptic drugs.…”

“…However, all these previous studies have focused only on the description of epilepsy found in a select group of patients with refractory epilepsy, while they have not analyzed whether there are patients with a less severe phenotype. In addition, despite new data in larger cohorts, 13,14 there is not much information about whether there might be clinical features that differentiate epilepsy associated with temporal encephalocele from other temporal epilepsies. Therefore, to better delineate the associated syndrome, first, we included in this study patients with RFE and patients with focal epilepsy that was controlled on antiepileptic drugs.…”