Endoscopic Endonasal Approach for Resection of Middle Fossa Encephalocele for Treatment of Refractory Temporal Lobe Epilepsy

Background: Epilepsy is one of the most common neurologic disorders and Temporal Lobe Epilepsy (TLE) is the most common type of focal onset epilepsy. TLE is more commonly associated with tumors, hemorrhage, scarring as a result of trauma history, and mesial temporal sclerosis. Anti-epileptic drugs (AEDs) are the mainstay of treatment in most cases but as many as one-third of patients will have medically refractory disease. Medically refractory epilepsy is an unusual presentation of cranial fossa dehiscence with resultant encephaloceles. Here we report a case series of medically refractory TLE secondary to a middle fossa encephalocele with the associated progression of electroencephalogram (EEG) and magnetic resonance imaging (MRI) findings.

Methods: Three patients (two adults and one pediatric patient) with intractable epilepsy were identified in a tertiary academic center over the past three years. All patients were found to have sphenoid bone dehiscence with left temporal lobe encephalocele. All patients had unremarkable physical examination findings. One patient had a history of head injury as a child but otherwise there were no predisposing factor identified in the other patients. Seizure frequency occurred weekly in the adults and monthly in the pediatric case despite appropriate antiepileptic medication dosage. All patients underwent endoscopic endonasal surgical approach with resection of the encephaloceles.

Results: All patients underwent video EEG monitoring with surgical evaluation including MRI brain and single-photon emission computed tomography (SPECT). MRI brain identified a left temporal lobe enecphalocele. All patients had complete resection of the encephalocele with repair of the cranial fossa dehiscence. All patients had resolution of their epilepsy. There was no CSF leak or postoperative complication.

Conclusion: Middle fossa encephalocele is a rare etiology for medically refractory TLE and may be easily missed. Neurosurgical consultation after failed AED regimens is appropriate in these rare cases and surgery can be a highly effective treatment.