Occult Middle Fossa Encephaloceles in Patients with Temporal Lobe Epilepsy

OBJECTIVE: Middle fossa encephaloceles are rare structural defects previously reported to cause complex partial seizures. Their debated etiology is either by failed union of temporal and sphenoid bone ossification centers or by erosion of the middle fossa floor secondary to pressure phenomena. Although magnetic resonance imaging (MRI) often reveals abnormalities, the actual encephalocele may not be identified preoperatively. METHODS: We present three cases of middle fossa encephaloceles that were identified intraoperatively and provide a review of the relevant literature. RESULTS: All three of our case presentations demonstrate patients with medically intractable epilepsy and intraoperative findings of middle fossa encephaloceles. In all patients, careful retrospective analysis of preoperative imaging provided clues to these encephaloceles, although none were suspected before surgery. After resection of the area all patients had improved seizure outcome. CONCLUSION: Middle fossa encephaloceles should be recognized as a potential source of epileptic pathology in patients with complex partial seizures. Although only 12 cases are reported in the literature, we believe that this phenomenon may be more common than previously recognized. We suggest that simple resection of the encephalocele alone may result in long-lasting, excellent seizure outcomes without amygdalohippocampectomy.