Endoscopic endonasal depth EEG-guided resection of a temporal encephalocele resulting in seizure freedom: illustrative case.

backgroundTemporal encephaloceles (TEs) are increasingly recognized as epileptogenic lesions in drug-resistant temporal lobe epilepsy. However, endoscopic endonasal surgery performed primarily to resect epileptogenic lesions remains extremely rare, largely because defining the optimal extent of resection is challenging without direct electrophysiological confirmation. OBSERVATIONS: A 41-year-old right-handed man presented with drug-resistant focal impaired consciousness seizures. MRI revealed a right TE herniating into the lateral recess of the sphenoid sinus. Scalp EEG suggested seizure onset in the right anterior temporal region with no evidence of a widespread temporal epileptogenic network. Through an endoscopic endonasal transpterygoid approach, the encephalocele and adjacent temporal dura mater were exposed. Depth electrodes placed into the encephalocele and adjacent cortex demonstrated frequent spikes in both sites, confirming epileptogenicity. The encephalocele and a 7-mm margin of adjacent cortex were resected, followed by multilayer skull base reconstruction. The patient experienced no complications and remained seizure free for 48 months. LESSONS: Endonasal depth EEG enables direct confirmation of epileptogenicity in encephalocele-associated epilepsy and supports minimally invasive, tailored lesionectomy. In appropriately selected patients, particularly those without evidence of a widespread mesial temporal epileptogenic network, use of an endoscopic endonasal approach may avoid craniotomy while achieving durable seizure freedom. https://thejns.org/doi/10.3171/CASE25965.