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Extratemporal epilepsies mimicking temporal mesial epilepsy
D Taussig1, A M Petrescu1, A Herbrecht2
1Université Paris Saclay-APHP, Neurophysiologie et Epileptologie, Le Kremlin Bicêtre, France.
Abstract:
Among patients with focal seizures of mesial temporal semiology, approximately 30 % experience persistent seizures after anterior temporal resections. The causes are multiple, including unrecognized extratemporal seizure onset. We report six patients from three tertiary care centres for drug-resistant epilepsy whose clinical semiology was mesial temporal but who were found to have an extratemporal seizure onset confirmed by stereoelectroencephalography (SEEG). Three patients were non-lesional, and three had mesial parietal lesions. In three patients (two lesional, one non-lesional), the conclusion of the non-invasive data was mesial parietal epilepsy, based on video-electroencephalograms (EEG) in two patients and a positron emission tomography (PET)-scan in one patient. In two non-lesional patients, the combined non-invasive data led to the hypothesis of temporal epilepsy. In the sixth patient, the main hypothesis was left temporal epilepsy, based on the video-EEG and PET-scan, despite a probable mesial parietal focal cortical dysplasia. SEEG finally led to the diagnosis of mesial parietal epilepsy in five patients and fronto-polar in the sixth. The mechanism of rapid temporal involvement is certainly not unique. Careful analysis of non-invasive data can correct a misdiagnosis of mesial temporal epilepsy but may not be able to do so in our cases, as in the literature. The systematic use of mesial parietal and mesial frontal electrodes, notably cingulate, in the investigation of non-lesional temporal lobe epilepsy with SEEG should be implemented in a prospective study.
Insights
Many patients with drug-resistant epilepsy initially suspected as having mesial temporal lobe epilepsy actually have extratemporal seizure onsets. Stereoelectroencephalography (SEEG) is crucial for accurate diagnosis, revealing parietal or frontal origins in these cases.
Area of Science:
- Neurology
- Neurosurgery
- Epileptology
Background:
- Approximately 30% of patients with focal seizures exhibiting mesial temporal semiology continue to experience seizures post-anterior temporal resection.
- Unrecognized extratemporal seizure onset is a significant factor contributing to persistent seizures after surgery.
- Accurate localization of seizure onset is critical for effective epilepsy treatment.
Purpose of the Study:
- To investigate cases where clinical semiology suggested mesial temporal epilepsy but stereoelectroencephalography (SEEG) revealed extratemporal seizure origins.
- To highlight the limitations of non-invasive diagnostic methods in accurately identifying seizure onset zones in complex epilepsy cases.
- To emphasize the importance of SEEG in diagnosing drug-resistant epilepsy with atypical semiology.
Main Methods:
- Retrospective analysis of six patients with drug-resistant epilepsy and mesial temporal semiology from three tertiary care centers.
- Confirmation of seizure onset using stereoelectroencephalography (SEEG).
- Review of non-invasive investigations including video-electroencephalograms (EEG) and positron emission tomography (PET)-scans.
Main Results:
- SEEG identified extratemporal seizure onsets in all six patients initially suspected of having mesial temporal epilepsy.
- Five patients were diagnosed with mesial parietal epilepsy, and one with fronto-polar epilepsy upon SEEG confirmation.
- Non-invasive data were misleading in several cases, suggesting temporal lobe epilepsy or mesial parietal epilepsy, underscoring diagnostic challenges.
Conclusions:
- Clinical semiology alone can be deceptive, leading to misdiagnosis of mesial temporal epilepsy when the origin is extratemporal.
- Stereoelectroencephalography (SEEG) is essential for accurate localization in drug-resistant epilepsy cases where non-invasive methods are inconclusive.
- Prospective studies investigating the systematic use of specific electrodes in SEEG for non-lesional temporal lobe epilepsy are warranted.
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