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

OBJECTIVE: We aimed to assess the ability of semiautomated electric source imaging (ESI) from long-term video-electroencephalographic (EEG) monitoring (LTM) to determine the epileptogenicity of temporopolar encephaloceles (TEs) in patients with temporal lobe epilepsy. METHODS: We conducted a retrospective study involving 32 temporal lobe epilepsy patients with TEs as potentially epileptogenic lesions in structural magnetic resonance imaging scans. Findings were validated through invasive intracerebral stereo-EEG in six of 32 patients and postsurgical outcome after tailored resection of the TE in 17 of 32 patients. LTM (mean duration = 6 days) was performed using the 10/20 system with additional T1/T2 for all patients and sphenoidal electrodes in 23 of 32 patients. Semiautomated detection and clustering of interictal epileptiform discharges (IEDs) were carried out to create IED types. ESI was performed on the averages of the two most frequent IED types per patient, utilizing individual head models, and two independent inverse methods (sLORETA [standardized low-resolution brain electromagnetic tomography], MUSIC [multiple signal classification]). ESI maxima concordance and propagation in spatial relation to TEs were quantified for sources with good signal quality (signal-to-noise ratio > 2, explained signal > 60%). RESULTS: ESI maxima correctly colocalized with a TE in 20 of 32 patients (62.5%) either at the onset or half-rising flank of at least one IED type per patient. ESI maxima showed propagation from the temporal pole to other temporal or extratemporal regions in 14 of 32 patients (44%), confirming propagation originating in the area of the TE. The findings from both inverse methods validated each other in 14 of 20 patients (70%), and sphenoidal electrodes exhibited the highest signal amplitudes in 17 of 23 patients (74%). The concordance of ESI with the TE predicted a seizure-free postsurgical outcome (Engel I vs. >I) with a diagnostic odds ratio of 2.1. SIGNIFICANCE: Semiautomated ESI from LTM often successfully identifies the epileptogenicity of TEs and the IED onset zone within the area of the TEs. Additionally, it shows potential predictive power for postsurgical outcomes in these patients.

Transient global amnesia after the right temporal epilepsy surgery: A case report.

Transient global amnesia (TGA) is characterized by sudden and temporary memory impairment, while transient epileptic amnesia (TEA) represents amnestic attacks as the main manifestation of focal epilepsy with presumed temporal origin. We present a 48-year-old patient who experienced transient amnesia 10 weeks after right selective amygdalo-hippocampectomy for right temporal lobe epilepsy. Despite TEA being a plausible explanation for amnesia in patients with temporal lobe epilepsy, no epileptiform discharges were found during the amnestic episode and key features indicative of TGA, including long duration, isolated occurrence, and dense anterograde amnesia of the episode, argued against a diagnosis of TEA in this case. Notably, the patient has remained seizure-free (now 4,5 years) and stopped taking antiseizure medication 32 months after surgery. Although TGA clinical criteria formally exclude patients with recent active epilepsy, neurologists should be aware that TGA can occur after epilepsy surgery in the temporal lobe. Therefore, we consider it of high clinical relevance to establish a careful differential diagnosis between TGA and epileptic amnestic attacks after epilepsy surgery to avoid unnecessary reintroduction or continuation of antiseizure medication. Additionally, this case presents the first comparison of detailed neuropsychological test results before and after a presumed TGA episode, revealing a complete recovery of anterograde memory functions within 1 day. PLAIN LANGUAGE SUMMARY: A 48-year-old patient experienced an episode of transient amnesia 10 weeks after epilepsy surgery. Given the patient's history, an epileptic origin of the episode initially seemed likely. However, tests revealed no seizure activity during the episode and the characteristics matched a condition called transient global amnesia. This case highlights the importance of correctly diagnosing memory impairments after epilepsy surgery to prevent unnecessary treatment.