Abstracts

Rationale: Refractory seizures sometimes arise from deeper foci within the brain and are difficult to detect on scalp EEG, thus reducing the chances of a successful epilepsy surgery. We describe 2 patients with scalp negative seizures studied with intracranial EEG who did well with responsive neurostimulation.

Methods: Both patients underwent comprehensive presurgical evaluation and were found to have scalp EEG negative seizures. We consented both patients and performed chart reviews on them.

Results: Patient I was a 29 yo F, had right temporal lobectomy at age 12, with 5 years of seizure freedom before recurrence. VNS achieved minimal benefit. MRI brain showed prior right temporal lobectomy. PET defined metabolic deficits in right mesial/lateral temporal region associated with prior surgeries. Scalp EEG revealed no changes with her events. MEG was unremarkable. Neuropsychological testing showed decline in core verbal function and memory function. IAP / Wada revealed left hemisphere dominance for language and memory. She underwent SEEG implantation with extensive right hemispheric coverage that captured multiple typical FIAS and FAS seizures with onset and early involvement of Right posterior cingulate and Right posterior insular regions. Brain mapping and cortical stimulation revealed motor function in right posterior cingulate regions and sensory functions in the insular regions precluding resection/laser ablation. She underwent RNS implant with 2 depth electrodes in the right posterior insular and right posterior cingulate regions and remains seizure free 4 months after implantation.

Patient II was a 33 yo F presenting with FTBTC with arousal from sleep followed by laughing/cursing and vocalization of ‘I love you’ followed by hypermotor movements of all extremities with mild left predominance progressing to tonic-clonic convulsion. MRI showed a 6 mm venous angioma in the right posterior frontal lobe. Scalp EEG revealed multiple seizures with hypermotor semiology, without a clear EEG correlate. PET revealed decreased uptake in the right posterior parasagittal frontal lobe and right inferior parasagittal frontal lobe. MEG was unremarkable. Neuropsychological testing reflected weakness of bi-frontotemporal systems. IAP / Wada revealed left hemisphere dominance for language and memory. She underwent SEEG implantation with extensive bilateral coverage over frontal regions, that captured multiple typical hypermotor seizures with early involvement of the right orbitofrontal region and rapid spread to right hippocampal regions. She underwent RNS implantation with 2 depth electrodes placed in the right orbitofrontal and right hippocampal regions for neuromodulation. She has currently achieved 30% seizure reduction 3 months after implantation and hopes to achieve better seizure control in future.

Conclusions: Scalp EEG negative seizures remain challenging conditions to treat. SEEG can perform admirably in delineating the seizure network and localizing the seizure onset zone. Better understanding of seizure networks in these patients may offer the ability to treat using neuromodulation or targeted therapies like ablation.

Funding: Please list any funding that was received in support of this abstract.: No funding was obtained for this research.