Abstracts

Rationale: Surgical resection is considered the first line option for treating intractable epilepsy. Surgical treatment is usually discouraged, when non-invasive approaches cannot provide adequate lateralization. Bilateral intracranial EEG (iEEG) survey has been proven to be a safe and effective option for addressing such cases. Conventionally, bilateral intracranial electrode placement is implemented through small bilateral burr holes or vertex craniotomy. However, it provides limited access and constrains the electrode coverage for revealing the possible seizure focus. An additional unilateral craniotomy is usually required to place more electrodes for precise localization after the initial lateralization survey. This increases the number of surgeries and the duration of iEEG monitoring. We present an alternative approach using bilateral craniotomy for electrode placement. This approach provides broad access to both hemispheres with an opportunity for extensive intracranial electrode coverage facilitating precise localization of seizure focus and functional mapping. Methods: We retrospectively reviewed 10 pediatric patients with drug-resistant epilepsy who underwent bilateral craniotomy for iEEG monitoring. Because all non-invasive diagnostic methods, such as various neuroimaging modalities (MRI, PET and SPECT) and scalp video electroencephalography, did not effectively lateralize seizure focus, a bilateral survey was proposed. A bilateral craniotomy with reverse question mark incision was performed to provide access for subdural electrode placement. The wide incision allowed comprehensive subdural grid and strip coverage on both hemispheres (figure 1). Results: The number of intracranial electrodes placed in each patient ranged from 152 to 224 (171±32— mean ± std). The duration of iEEG monitoring ranged from 3 to 30 days with an average 11±8.5 (std) days. Seizure foci were found in 8 patients who underwent subsequent resective surgery. Seizure focus was not localized in the other 2 patients through the initial bilateral iEEG monitoring. These two patients subsequently underwent a complete corpus callosotmy (CC) followed by additional iEEG monitoring. Resective surgery was performed on these two patients as the post-callosotomy iEEG successfully lateralized and localized the ictal onset zone. One patient developed infection requiring IV antibiotics. Conclusions: Bilateral craniotomy provides wide access for comprehensive bilateral subdural electrode implantation. Our experience with 10 pediatric patients suggests that this procedure can be carried out safely and effectively for localization of focal seizure origin with prolonged iEEG monitoring. This approach could broaden the availability of epilepsy surgery and might improve overall surgical outcomes.