Abstracts

Rationale: Drug-resistant epilepsy (DRE) can be challenging to address surgically despite advances in presurgical assessment technology. Although not always possible, using a mixture of well-established techniques (e.g., MRI, fMRI, EEG, PET) can be complemented by including novel techniques, such as electrocortical stimulation mapping (ESM, “electric Wada”) and measurement of changes in gamma oscillations during cognitive tasks using stereoencephalography (sEEG). We present data on a patient who experienced no improvement in seizure burden, despite undergoing an initial resection that used well-established presurgical assessment methods. The patient then underwent a second presurgical assessment with the addition of ESM and gamma activation measurement techniques.

Methods: A right-handed, 10-year-old male with a history of focal epilepsy underwent a right parietal craniotomy for seizure management. Prior to his initial resection, an MRI was normal and a PET scan showed hypometabolism involving the right parietal temporal operculum and insula. Neuropsychological testing showed average scores and was nonlateralizing except for left-sided fine motor weakness. EEG studies showed right-sided focal slowing in the interictal period and seizure onset in the right posterior quadrant. The patient’s parents were offered sEEG, or resection with intraoperative electrocochleography (ECoG), for which they chose the latter. The patient continued to have seizures postoperatively and a second surgical workup was conducted 4 months postoperatively and included a brief, focused neuropsychological evaluation, gamma activity and electrocortical stimulation mapping using sEEG, PET, and EEG.

Neuropsychological findings revealed poorer performances on visual constructional, visual organization, and fine-motor tasks. Gamma oscillation mapping showed increased activation in the parietal-occipital notch (H8-10), especially during tasks involving scanning of faces and complex patterns. No interruption of cognitive performance was seen during ESM on cognitive tasks (visual, verbal, motor, etc.). PET showed hypometabolism corresponding to the right anterior temporal pole and insular cortex. EEG studies identified frequent, independent sleep-potentiated sharp/spike waves in the right hemisphere.

Results: Based on aggregate data from presurgical techniques used with this patient prior to the second resection, seizure onset was believed to be in the right parietal operculum and surrounding posterior perisylvian region in the suprasylvian cortex. Therefore, an ECoG-guided resection of the right parietal-temporal area, posterior insula, and aspects of the convexity was conducted. Surgery was uncomplicated.

Patient’s seizure burden significantly improved following his second surgery with only three brief episodes lasting 15 to 30 seconds reported in the 2 months, which did not progress to more severe, prolonged events as they had prior his second surgery.

Conclusions: Results from this case study highlight the benefit of using both novel and established techniques when assessing presurgical DRE patients and how this information may be used to guide surgery and inform potential functional outcomes for patients.

Funding: Please list any funding that was received in support of this abstract.: n/a.