Temporal encephalocele: a rare but treatable cause of temporal lobe epilepsy

Abstract

Objective. Although rare, temporal encephalocele is an important causative agent in surgically remediable drug‐refractory epilepsy. The ideal treatment for temporal encephalocele remains unclear with a variety of resective surgeries recommended. Here, we analyse patient data on temporal encephalocele with a view to highlighting diagnostic clues and management strategies. Methods. Comprehensive databases at Deenanath Mangeshkar Hospital, Pune from January 2015 to June 2019 were reviewed for this observational study. Of 107 temporal lobe epilepsy surgery patients, nine individuals with temporal encephalocele were identified, who formed the study cohort. Their clinical, neuropsychological, EEG, imaging and long‐term outcome data were analysed. Results. The study cohort consisted of seven males and two females with a mean age of 22 years. Epilepsy onset age varied from 4.5 to 19 years. Seven patients had focal non‐motor seizures with impaired awareness, while two patients had focal motor seizures. Temporal encephalocele detection by MRI was reported in only two patients, and was missed in seven individuals. Three patients underwent standard anterior temporal lobectomy while the remaining six underwent resection of the temporal encephalocele with surrounding temporal pole. Eight patients showed Engel Class I outcome and one showed Class IIa outcome after a mean follow‐up duration of 27 months (17‐44 months). Histopathology confirmed gliosis in seven, hippocampal sclerosis type I in one and suspicious dyslamination with prominent gliosis in one patient. Six of eight patients reported an improvement in their psychological state (mood, anxiety and motivation) over time. Significance. A careful review of MRI in patients with temporal lobe epilepsy is necessary, followed by investigations for the presence of an encephalocele. When temporal lobe epilepsy is associated with encephalocele, tailored resection of the encephalocele and the surrounding temporal pole, sparing mesial temporal structures, demonstrates excellent long‐term clinical and neuropsychological outcome.

Temporal encephalocele: An epileptogenic focus confirmed by direct intracranial electroencephalography

“…The epileptogenic potential of these lesions may be secondary to cortical irritation, secondary inflammation and gliosis and also associated lesions [1] . Multiple studies provide indirect evidence in support of this theory with reports of limited lesionectomy, corticectomy and bone repair resulting in favorable post-surgical outcomes [5] , [6] , [8] , [9] , [13] , [20] without removal of mesial temporal structures or neocortical temporal lobe structures typically resected in a standard anterior temporal lobectomy.…”

“…Several studies have suggested the epileptogenic potential of encephaloceles and surrounding cortex presumed to be due to local irritation, traction, scarring or associated secondary lesions [1] . Several studies have noted favorable seizure outcomes with limited resections further providing evidence of the potential epileptogenicity of encephaloceles [1] , [2] , [3] , [4] , [5] , [6] , [7] , [8] . However, to our knowledge there is limited literature providing evidence with chronic intracranial monitoring that an encephalocele is in the seizure onset zone [9] , [10] .…”

Neuroimaging of Brain Tumor Surgery and Epilepsy

“…Yamazaki K et al published a case report about rare frontal encephaloceles presenting with epilepsy treated surgically. "Encephaloceles" are known to be associated with epilepsy, but mostly, they are located in the temporal lobe [34][35][36][37][38][39] and are rarely located in the frontal lobe [40,41]. The authors demonstrated the clear findings of the MRI, PET and electroencephalography of rare encephaloceles in frontal lobes and their successful surgical treatment via frontal lobectomy.…”

Semiautomated electric source imaging determines epileptogenicity of encephaloceles in temporal lobe epilepsy

“…They have been identified as a potential cause of temporal lobe epilepsy (TLE), but their epileptogenicity needs further confirmation. 1,2 The true prevalence of temporal encephaloceles (TEs) is likely underestimated. The largest case series to date estimates the prevalence to be between 2% and 4% in general presurgical evaluation of epilepsy patients and up to 10% in drug-resistant TLE patients.…”

“…Encephaloceles are herniations of brain tissue, typically occurring at the temporal pole in combination with skull defects of the sphenoid bone. They have been identified as a potential cause of temporal lobe epilepsy (TLE), but their epileptogenicity needs further confirmation 1,2 . The true prevalence of temporal encephaloceles (TEs) is likely underestimated.…”