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[Surgery for intractable epilepsy in children: pre- and perioperative evaluations with special reference to dipole
Insights
Preoperative evaluation for pediatric epilepsy surgery utilizes EEG-video monitoring and MR imaging. Advanced dipole tracing accurately identifies epileptic foci, improving surgical outcomes and seizure control in children.
Area of Science:
- Pediatric Neurosurgery
- Epileptology
- Neuroimaging
Background:
- Intractable epilepsy in children poses significant challenges requiring precise surgical intervention.
- Accurate preoperative and perioperative evaluation is crucial for successful epilepsy surgery outcomes.
Purpose of the Study:
- To describe diagnostic methods for surgical treatment of intractable epilepsy in children.
- To evaluate the efficacy of non-invasive and invasive techniques in localizing epileptic foci.
Main Methods:
- EEG-video monitoring as a fundamental non-invasive diagnostic tool.
- Magnetic Resonance (MR) imaging for amygdalohippocampal volume measurement and differential diagnosis.
- Dipole tracing with realistic head models to estimate equivalent current dipoles (ECDs) from scalp EEG interictal spikes.
- Electrical cortical stimulation with intracranial electrodes to map eloquent brain areas.
Main Results:
- MR imaging aids in differentiating mesial temporal lobe epilepsy (TLE) from lateral TLE and generalized epilepsy.
- Dipole tracing accurately localized epileptic foci, with ECDs concentrated near lesions (70-90%) and a mean distance of 14 mm from the seizure onset zone.
- Postoperative seizure freedom was achieved in 75% of patients, with neuropsychological deficits resolving within one year.
Conclusions:
- A combination of advanced imaging and electrophysiological techniques enables precise localization of epileptic foci in pediatric epilepsy surgery.
- Current methods achieve good seizure control, but further improvements are needed for optimal outcomes.
Abstract:
Methods of preoperative and perioperative evaluation methods for surgical treatment of intractable epilepsy in children are described. Among non-invasive diagnostic methods, EEG-video monitoring is the most fundamental. Amygdalohippocampal volume measurement by MR was useful for the differential diagnosis of mesial temporal lobe epilepsy (TLE) from lateral TLE and generalized epilepsy. The dipole tracing method with a realistic head model was useful for identification of epileptic foci from the interictal spikes of scalp EEG, when an abnormal electric source was estimated as an equivalent current dipole (ECD) in the brain of patients with organic lesion and TLE. ECD concentration ratio ranged from 70 to 90% within 20 mm around the lesion. After lesionectomy seizures disappeared in every patient. The mean distance between the centers of the ECD and epileptic focus (identified by subdural electrode recording) was 14 mm (range: 8 to 18 mm). ECDs of mesial TLE were located in the temporal base rather than mesial temporal lobe, whereas those of lateral TLE in the lateral cortex precisely. In unilateral, intermediate and bilateral TLE, 76%, 52% and 36% of ECDs were localized in the ictal onset zone respectively (p = 0.007). Electrical cortical stimulation with chronically placed intracranial electrodes was used to accurately identify eloquent areas to avoid postsurgical complications. Immediately after operation, 10 to 20% of patients showed better or deteriorated results in neuropsychological examinations, which recovered in all patients after one year. Postoperative seizures were absent in three fourths of patients. Further efforts are needed to obtain better seizure control in future.