Introduction: Patients with medically refractory epilepsy are often referred for neurosurgical intervention, including surgical resection, or open loop stimulation such as vagal nerve stimulation. For bilateral hippocampal sclerosis, resection is typically unilateral due to severe cognitive deficits associated with bilateral resection. Studies have demonstrated the use of subdural electrodes to establish laterality of the majority of seizures, followed by unilateral resection, however patients often have recurrence. We therefore placed a closed loop responsive neurostimulator device, and report on technical aspects, outcomes and electrographic recordings.
Methods: A 44yo Caucasian male was referred to the neurosurgical service for bilateral mesial temporal sclerosis and medically refractory epilepsy. He underwent extensive EEG assessment and bilateral ictal onset was noted, with no clear laterality. Bilateral mesial temporal electrodes were placed using the Nexframe and intra-operative CT. His ictal activity was recorded post-operatively and correlated to his seizures, allowing electrocorticographic correlation of each individual seizure subtype.
Results: This patient endorsed 5 different seizure semiologies, including simple partial seizures, complex partial seizures, and 3 further subtypes he classified as “jolts”, auras, and a feeling of dissociation. Using the implanted responsive neurostimulator, we obtained bilateral temporal electrocorticography and noted rhythmic high amplitude activity correlating with each seizure type. In terms of laterality of his events, 51.4% were left sided, 15.0% were right sided and 33.6% were indeterminate.
Conclusions: Our experience with a responsive neurostimulator device, using intra-operative CT and Nexframe guided placement suggests that this novel described method is safe and accurate. We obtained highly accurate electrocorticography related to both mesial temporal lobes, and correlated this with the patient’s seizure semiology, an unprecedented level of analysis permitted by implantation of a closed-loop system. Such systems potentially herald tailored epilepsy management for individual patients.
Patient Care: This research establishes the use of novel closed loop neurostimulator systems, both describing technical notes for surgical placement, and novel nuances of ambulatory post-operative electrocorticography. The use of closed loop neurostimulator systems heralds a new era that permits individually tailored seizure therapy.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) describe the possible indications for responsive neurostimulator placement for epilepsy
2) understand the distinction between closed and open loop systems
3) consider the use of novel technical methodology using intra-operative CT and guidance systems for electrode placement
References: Cukiert A, Cukiert C, Argentoni M et al. Outcome after cortico-amygdalo-hippocampectomy in patients with severe bilateral mesial temporal sclerosis submitted to invasive recording. Seizure 2009; 18.
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Burchiel KJ, McCartney S, Lee A, Raslan AM. Accuracy of deep brain stimulation electrode placement using intraoperative computed tomography without microelectrode recording. Journal of neurosurgery