Left Temporal Pole Encephalocele With Independent Hippocampal Seizures: Surgical Strategy and Relevance of Epileptic Biomarkers.

Temporal pole encephalocele (TE) is an increasingly recognized surgically treatable subtype of refractory temporal lobe epilepsy that rarely shows hippocampal involvement. A 27-year-old patient presented with medically intractable epilepsy because of a left temporal pole encephalocele with a normal hippocampus on MRI. Extraoperative electrocorticography showed independent seizure onset with distinct morphology of seizure onset pattern from the temporal pole encephalocele and hippocampus. Additional analysis of ictal and interictal fast ripples revealed different electrophysiological fast ripple profiles in the two seizure onset zones. The patient underwent temporopolar disconnection, eliminating the need for large dural repair and multiple hippocampal transections that helped preserve the intrahippocampal and extrahippocampal memory pathways. Herein, the authors report that independent hippocampal seizures can be observed in patients with temporal pole encephalocele. Features of the ictal and interictal fast ripples can differ depending on the morphology of the seizure onset pattern. The authors suggest that, the interpretation of fast ripples in clinical practice should take seizure onset patterns into consideration.