Temporal encephaloceles can be missed in patients with refractory temporal lobe epilepsy

Temporal encephaloceles (TEs) are one of the cause of refractory temporal lobe epilepsy (TLE). We reviewed the neuroimaging and video-electroencephalography (EEG) records of epilepsy patients who underwent temporal lobectomy in our center to investigate frequency of TEs. We retrospectively reevaluated 294 patients who underwent epilepsy surgery in our tertiary epilepsy centre between January 2010 and March 2019 and included 159 patients (78 females, 49 %; 81 males) who had temporal lobectomy. Preoperatively, TEs were reported in 3 of 159 patients (1 female, 2 males). After reevaluation 4 more patients with TEs (1 female, 3 males) were added. The ratio of TE in patients who underwent temporal lobectomy increased from 1.8 % (n=3) to 4,4 % (n=7). The median ages were 18 (range 16-22) versus 10 years (range 5-17) at habitual seizure onset and the median of epilepsy duration was 5 (range 3-15) versus 175 (range 11-25) years between patients with and without TE. Habitual seizure onset age was significantly higher (p =, 007) in the patients with encephalocele and epilepsy duration was shorter (p =, 003) than patients without encephalocele. The ictal EEG records of all patients TE rhythmic delta activity which is suggested neocortical temporal lobe onset seizures. 4 of 7 patients' PET imaging showed temporal lobe hypometabolism compatible with ipsilateral to the TEs. The three patients underwent anterior temporal lobectomy without amygdalohippocampectomy and others had anterior temporal lobectomy with amygdalohippocampectomy. We suggested that there might be some clues for temporal encephalocele, an easily overlooked cause in patients with nonlesional temporal lobe epilepsy.TLE patients with TE had relatively late onset of epilepsy and rhythmic delta activity on ictal EEG. Also, temporal hypometabolism on PET may be a useful key to suspicion of TE.