Abstracts

Rationale: The developmental anomalies that underpin some temporal lobe epilepsies may co-exist with a defect in skeletal formation. This entitity - Temporal Lobe Epilepsy with Encephalocele (TLEE) comprises of a herniation of cerebral contents into the infratemporal fossa or sphenoid bone. A handful of reports of TLEE exist in the literature. Our goal here is to contribute to the understanding and management of this not uncommon, but underdiagnosed syndrome.Methods: A review of an adult surgical database compiled over the past 7 years at the UT comprehensive epilepsy program was carried out and all cases where imaging or surgical findings revealed TLEE were identified. Demographics, semiologic, electrophysiologic, surgical data and outcomes were all compiled.Results: 9 patients with TLEE were identified (6 women). Mean age at onset of epilepsy was 36 years, mean age at surgery was 47 years. 66% had complex partial seizures as the predominant seizure type; 33% had complex motor seizures. All failed a minimum of three anticonvulsant agents prior to surgery. Only one had evidence of CSF leakage. Scalp EEG revealed interictal discharges that were anterior temporal in 6, generalized in 2; absent in 1. Ictal onsets were localized to the lesional temporal lobe in 4, lateralized in 1, bitemporal in 1, non localizable in 2 and not recorded in 1. Imaging revealed abnormalites in 7 cases (fig 1). Osseous abnormalities were demonstrated in the greater wing of the sphenoid bone, base of the pterygoid processes, and in the lateral wall of the sphenoid sinus. Bony defects ranged from 3 to 30 mm. In the two 'imaging-negative' patients, TLEE was diagnosed intra-operatively and confirmed retrospectively as being present on MRI scans. In the 4 patients PET scans were acquired. Focal or regional hypometabolism was detected in the vicinity of all of the encephalocele, including the two in whom the lesion was not evident on preoperative imaging. Surgical strategies included intracranial electrode placement in 3 cases, and the use of a zygomatic osteotomy to facilitate repair in 3 of the others. Postresection electrocorticography was done in 8, and revealed evidence of residual spiking over the hippocampus or parahippocampal gyrus in 4 cases, and no abnormalities in the other 4. Resections were not extended to remove areas with spiking. Average follow was 15 months (all but one patient had at least 6 month follow-up). 8 patients had an Engel 1a outcome; one had an Engel 1d outcome. Conclusions: TLEE falls under the general rubric of neocortical temporal lobe epilepsy. Our series suggested that this condition presents with onset much later in life than typical TLE, the imaging shows a apectrum of changes and can be subtle. The epilepsy involves other temporal lobe structures besides the overt abnormality, but responds quite well to lesionectomies. The use of a zygomatic osteotomy allows for minimizing the neocortical resection and allows for an optimal repair of the middle cranial fossa defect. We combine our data with others in the literature to generate a management algorithm for this intriguing and curable epilepsy syndrome.