MRI-Guided Laser Therapy for Refractory Focal Epilepsy in a Patient with a Fully Implanted RNS System
Abstract number :
2.039
Submission category :
3. Neurophysiology / 3E. Brain Stimulation
Year :
2021
Submission ID :
1826262
Source :
www.aesnet.org
Presentation date :
12/5/2021 12:00:00 PM
Published date :
Nov 22, 2021, 06:53 AM
Authors :
Vivek Buch, MD - Stanford University; Emily Mirro - NeuroPace Inc; David Purger, MD - Neurosurgery - Stanford University; Michael Zeineh, MD, PhD - Radiology - Stanford University; Babak Razavi, MD, PhD - Neurology & Neurological Sciences - Stanford University; Casey Halpern, MD - Neurosurgery - Stanford University
Rationale: The RNS System is an effective treatment for patients with refractory focal epilepsy1. Furthermore, the long-term intracranial EEG (iEEG) data provided by the RNS System can supplement the epilepsy evaluation for future surgical resection or ablation2. Unlike the previous model, the latest device model (RNS-320) has 1.5T MRI conditional approval. We performed a successful Laser interstitial thermal therapy (LITT) while the RNS cranially implanted neurostimulator and intracranial leads remained in place.
Methods: Given the potential for artifact limiting intraoperative thermography and because this was a first-of-its-kind procedure, an awake LITT (Visualase, Medtronic) was performed in a 1.5T MRI scanner in a patient with a fully implanted RNS neurostimulator and leads at Stanford University.
Results: Patient is a 26 yo RH female with medically refractory right temporal epilepsy. She was initially implanted with a right parietal RNS leads covering mesial, anterior and lateral temporal regions. Data from this subsequently led to an anterior temporal lobectomy (ATL) with two cortical strip leads repositioned to cover the posterior margin of the ATL. She continued to have 5-12 auras sometimes in daily clusters, some with loss of awareness. Post-resection imaging revealed residual piriform cortex3.
LITT was performed 11 months after the resection, during which the neurostimulator and leads remained in place. The procedure entailed asleep image-guided laser placement in the operating room (Figure 1a,b), followed by awake MRI-guided laser thermal ablation of remnant amygdala/piriform cortex. Real-time thermography was limited due to neurostimulator artifact (Figure 1c,d), but during test dosing (30% energy) and initial ablation (50% energy) the patient had a typical aura. This resolved with completion of the ablation. Post-operative imaging showed a good ablation zone within the mesial temporal remnant with extension to piriform cortex (Figure 2). The patient remained neurologically intact and was seizure free for 2 weeks. At 6 weeks post-LITT follow-up, she reported a significant reduction in seizure burden and auras, with subjective cognitive improvement.
Conclusions: This is the first experience with LITT performed in an adult patient with an RNS neurostimulator and leads. There were no known complications, with overwhelming improvement in seizures and quality of life. This approach supports new surgical possibilities for RNS System patients. Further, it underscores the (1) importance of considering the location of a potential future LITT when placing the neurostimulator to minimize MRI artifact in the region of interest, (2) utility of awake LITT for confirming that the ablation is within the epileptogenic network
References:
1. Razavi, B, Rao, VR, Halpern, CH, et al. Epilepsia, 2020
2. Hirsch, LJ, et al. Epilepsia, 2020
3. Galovic M, et al. JAMA Neurology, 2019.
Funding: Please list any funding that was received in support of this abstract.: None.
Neurophysiology