Abstracts

Rationale: Insular epilepsy is a well-known mimic of frontal, temporal and parietal epilepsy. Its diagnosis and treatment can be challenging due to the insula’s position in the cerebral central core near branches of the middle cerebral artery and the basal ganglia. We present three patients with semiology suggestive of lobar epilepsy who underwent insular resection after confirmatory intracranial electroencephalography (EEG).

Methods: We retrospectively reviewed three patients who underwent insular resection for epilepsy after confirmation with an intracranial EEG study. Imaging including magnetic resonance imaging (MRI), scalp EEG, neuropsychological testing, intracranial EEG, and surgical data were collected.

Results: In the three cases the patients presented with semiologies suggestive of extrainsular epilepsy including hypermotor and vocalization semiologies (frontal lobe), and scalp pain (parietal lobe). All patients were non-localizable based on non-invasive studies and subsequently received a combined intracranial depth and surface electrode study. A large grid electrode was used for extensive coverage of the frontal, temporal, and parietal lobes in order to definitively rule-out seizure onset in these locations. The grid was also used for stimulation mapping of sensory, motor, and language function and for seizure induction. Insular depth electrodes were placed in oblique and parasagittal trajectories for maximum coverage of the insula. Seizure onset was highly focal in the insula with spread to an adjacent cortical dysplasia in two cases. The depth electrodes were left in place for guidance during resection, allowing the surgeon to identify the seizure focus and prevent encroachment on the basal ganglia medially. Depth electrode-guided surgery was performed in all cases with no associated morbidity and with seizure freedom on short-term follow-up.

Conclusions: Insular epilepsy may present with semiology indicating seizure onset in other lobes. In all cases, the combined surface and depth study localized onset in the insula and ruled out alternative hypotheses. Stimulation mapping also helped to confirm seizure onset area. Depth electrode-guided insular resection is a safe and effective method to optimize resection of the seizure focus and prevent resection of the adjacent basal ganglia.

Funding: Please list any funding that was received in support of this abstract.: Department of Neurosurgery, Yale School of Medicine.