Abstracts

Rationale: In pharmaco-resistant cases of focal epilepsy who undergo pre-surgical workup for epilepsy surgery, intracranial EEG recording is usually an essential step to identify the seizure onset zone and eventually plan for surgical intervention. There has been some primary reports of delay of the time to the first seizure in patients after intracranial electrode implantation compared to the scalp EEG monitoring. We encountered an unusual case who did not have any seizure throughout the duration of EEG monitoring after stereotactic implantation of depth electrodes and remained seizure free afterwards without any surgical intervention. Methods: A 21-year-old left-handed female with 4 years history of pharmaco-resistant epilepsy underwent a comprehensive evaluation for epilepsy surgery. Clinically, her seizures manifested with an occasional aura of dizziness and feeling pressure in the head, followed by impaired consciousness and slight deviation of the eyes to the right. On a few occasions her seizures proceeded to a forced right head deviation and then secondary generalized tonic clonic seizure. Average frequency of her seizures were about 2 per month on 2 antiepileptic medications. Her MRI revealed a relatively large area of cortical dysplasia in the left perisylvian and insular region. Results: During the pre-surgical workup, findings of video EEG-monitoring, magnetoencephalogram (MEG) and positron emission tomography (PET) studies were all concordant in localizing the seizure onset zone to the area corresponding to the cortical dysplasia. Given the relatively large size of the cortical dysplasia, decision was made to proceed with intracranial monitoring for more accurate localization of the ictal onset zone. The patient underwent successful stereotactic implantation of 5 depth electrodes in the left insular region along with 2 electrodes in the left temporal and 1 electrode in the left frontal area with no complications. Patient was started on intracranial video-EEG monitoring on post-op day #1 and her antiepileptic medications were discontinued. Throughout the subsequent 17 days of video-EEG recording no clear interictal epileptiform discharges, or clinical or electrographical seizures were recorded. Provocative measures such as sleep deprivation, and caffeine intake which were historically associated with triggering a seizure in this patient were not successful in inducing a seizure. Intracranial depth electrodes were removed on day #17 with no complications. Patient was discharged home on her previous antiepileptic medications and in a stable condition. In the next 10 months and up to the time of writing this report she has remained seizure free. Conclusions: Although there has been some primary reports of a delay in the time to capturing first seizure during EEG monitoring after placement of depth electrodes, to the best of our knowledge there has not been a report of seizure remission in patients after implantation of depth electrodes. This effect is probably related to the mechanical interruption of neuronal networks and circuits involved in synchronization and propagation of ictal discharges. This case, especially in the setting of malformation of cortical development, raises the interesting question for future research in feasibility of identifying and interrupting selective circuits involved in ictal propagation and discharges with minimal surgical interventions. Funding: No funding