Summary: The presence of interictal epileptiform discharges (IEDs) in the outpatient interictal EEG can provide evidence for a diagnosis of epilepsy and support for a specific epilepsy syndrome. However, there is variation in the duration of outpatient EEGs, and prolonged EEGs may have a higher yield for IEDs. The authors retrospectively reviewed 172 routine, extended, outpatient EEGs of at least 60 minutes duration in adults to determine the time to the first IED. The mean duration was 187 minutes. Twenty-six percent captured IEDs. The initial IED occurred in the first 20 minutes in 53% and after 20 minutes in 47%. The mean time to the first IED was 32.8 minutes with a range of 1 to 216 minutes and a standard deviation of 48.2 minutes. Results were skewed to the right (skew 2.22) with a median time to the first IED of 10 minutes. There was a longer time to the first IED in temporal epileptiform discharges compared with generalized discharges.

The neurosurgical treatment of skull base temporal encephalocele for patients with epilepsy is variable. We describe two adult cases of temporal lobe epilepsy (TLE) with spheno-temporal encephalocele, currently seizure-free for more than two years after anterior temporal lobectomy (ATL) and lesionectomy sparing the hippocampus without long-term intracranial electroencephalogram (EEG) monitoring. Encephaloceles were detected by magnetic resonance imaging (MRI) and confirmed by maxillofacial head computed tomography (CT) scans. Seizures were captured by scalp video-EEG recording. One case underwent intraoperative electrocorticography (ECoG) with pathology demonstrating neuronal heterotopia. We propose that in some patients with skull base temporal encephaloceles, minimal surgical resection of herniated and adjacent temporal cortex (lesionectomy) is sufficient to render seizure freedom. In future cases, where an associated malformation of cortical development is suspected, newer techniques such as minimally invasive EEG monitoring with stereotactic-depth EEG electrodes should be considered to tailor the surrounding margins of the resected epileptogenic zone.