Abstracts

Rationale: Temporal Lobe Epilepsy with Encephalocele (TLEE) is a congenital lesional epilepsy that is increasingly recognized as not uncommon but underdiagnosed. Only a few small surgical series with limited follow-up on this condition have been reported. Indeed, it remains unclear from the existing publication whether this disorder should be as a lesion or with a traditional anterior temporal lobectomy (ATL) and amygdalo-hippocamepectomy (AH), and what the relative likelihood of seizure freedom with each of these approaches is. We present our experience with 24 patients managed surgically by us, their management and long term outcomes following lesionectomy versus ATLAH. Our series doubles the world’s literature of reported cases of TLEE.  Methods: A prospective database of epilepsy surgery cases identified 24 surgical cases of TLEE over a 12 year interval. Pre-operative characteristics, surgical technique, pathology and post-operative follow up were compiled. A systematic review of the current literature was also completed.  Results: 24 patients (16 women) with TLEE were identified. Mean age at seizure onset was 28, mean age at surgery 43 years. All failed a minimum of 3 anticonvulsant agents prior to surgery. Scalp EEG revealed interictal discharges that were anterior temporal in 22 patients, generalized in 1; and absent in 1. Ictal onsets were localized to the lesional temporal lobe in 21, bitemporal in 1, non localizable in 2. Imaging revealed abnormalities in 23 cases. In the one "imaging-negative" patient, TLEE was diagnosed intraoperatively. In 16 patients FDG-PET scans revealed focal or regional hypometabolism in the vicinity of all of the encephalocele. SEEG electrodes were placed in 5 cases, SD Grids in 7 cases. 15 patients underwent a standard ATLAH with repair of the defect, 9 had ATL with repair of defect.  In 5 cases, a zygomatic osteotomy was used to minimize neocortical resection in the dominant temporal lobe while resecting the encephalocele. Post-resection electrocorticography was done in 23, and revealed evidence of residual spiking over the hippocampus or para-hippocampal gyrus in 6 cases, and no abnormalities in the other 13. Average follow-up was 30 months. 19 patients had an Engle 1 outcome, 2 had Engle 2d outcome and 3 had Engle 3a outcome. Conclusions: TLEE may involves other temporal lobe structures besides the overt abnormality. Analysis of the published literature and our series provided 50 cases that allow for the design of an algorithm for the management of TLEE. This outlines the indications for intracranial monitoring, tailored resections, lesionectomies and targeting the mesial structures. Using this algorithm may minimize the likelihood of unintended cognitive deterioration in these cases, without compromising the desired impact on the epilepsy. Funding: none