Small temporal pole encephaloceles: a treatable cause of "lesion negative" temporal lobe epilepsy.

Epilepsy due to encephaloceles of the temporal pole may be an under recognized, treatable cause of refractory temporal lobe epilepsy (TLE). We describe three adult patients initially labeled "lesion negative" TLE. In all, video–electroencephalography (EEG) revealed ictal theta in the left temporal region and positron emission tomography (PET) showed temporal lobe hypometabolism, but neuropsychology revealed preserved verbal memory. Close inspection of structural magnetic resonance imaging (MRI) suggested subtle abnormalities at the tip of the left temporal lobe. High resolution computed tomography (CT) confirmed bony defects in the inner table of the skull. 3T MRI with fine coronal and sagittal slices indicated cerebrospinal fluid (CSF) and brain tissue protruding into the defects. All proceeded to resection of the temporal tip and became seizure free. Patients with "lesion negative" TLE should have careful review of images covering the temporal pole. If encephalocele is suspected, further imaging with high-resolution CT and MRI can be helpful. Temporal polar resection, sparing mesial structures, appears to be curative.