Early findings suggest that more than 50% of children who undergo magnetic resonance imaging (MRI)-guided laser interstitial thermal therapy (MRgLITT)—a novel and minimally invasive treatment modality for drug-resistant epilepsy—have seizure freedom at 1 year, according to new findings presented at the American Epilepsy Society virtual meeting, AES2020.

Neurology Learning Network caught up with the study’s lead author, Elysa Widjaja, MD, MPH, about these findings, their implications, and key areas of future research needed for this novel therapy. Dr Widjaja is a staff pediatric neuroradiologist and associate scientist at The Hospital for Sick Children in Toronto, and professor at the University of Toronto in Ontario, Canada.

Neurology Learning Network: Could you discuss MRgLITT as a novel treatment modality for pediatric drug-resistant epilepsy?

Dr Widjaja: MRgLITT involves placing a thin laser fiber through a small burr-hole in the skull into the lesion or the area responsible for epilepsy. Subsequently, the position of the laser fiber is confirmed on MRI. MRgLITT is done in the MRI suite, so that the area that is ablated can be directly visualized using real-time temperature monitoring in the MRI scanner. In this way, the lesion could be burned with great precision, with minimal injury to adjacent normal tissue. Further, temperature safety limits can be set to protect critical brain structures. Hospital stay following this minimally invasive treatment is shorter compared with surgery, and lasts an average of 2 days following MRgLITT compared with about 1 week after surgery.

MRgLITT is also particularly helpful with lesions located deep within the brain, such as hypothalamic hamartoma, as the thin laser fiber can reach deep-seated lesions with minimal damage to overlying normal brain tissue. However, not all children with focal drug-resistant epilepsy are suitable for MRgLITT. Children with large lesions in the brain may not be suitable for MRgLITT. For these children, surgery may be more appropriate.

NLN: The preliminary findings from your study have shown that more than half of children who underwent MRgLITT achieved seizure freedom at 1-year follow-up, and that permanent neurological deficits were a rare occurrence. Could you elaborate on these findings and their significance?

Dr Widjaja: To date, we have recruited 182 children who had undergone MRgLITT. One-year seizure outcome data was available in 137 children, of whom 54% achieved seizure freedom at 1-year follow-up. MRgLITT was used to treat a variety of lesions, such as cortical malformations, hypothalamic hamartoma, tumors, and hippocampal sclerosis. Twenty children have had 2 MRgLITT procedures, of whom 12 (60%) were seizure free at 1-year after the second MRgLITT procedure.

Complications relating to MRgLITT occurred in 28 patients (15%), including 13 (7%) cases of transient neurologic deficits and 2 cases (1%) of permanent neurologic deficits. No major intracranial hemorrhage was observed. Thirty-day mortality post-MRgLITT was reported in 1 patient (0.5%), and was found to be related to cerebral edema.

Comparatively, the literature indicates that following epilepsy surgery, 65% of children experienced seizure-freedom at 1-year follow-up, 5% had permanent neurological deficit, and 0.4% to 1.2% of patients died.

NLN: What were the limitations of this study?

Dr Widjaja: Although MR-guided laser therapy is increasingly used for the treatment of drug-resistant epilepsy among children, we do not know how well it works, among whom it will work, and what its complications are. While a randomized controlled trial comparing outcomes of MRgLITT to surgery would be the ideal study design, such a study may not be feasible and recruitment could be a challenge, as patients and families may prefer a less invasive procedure.

Our study is the first and largest multicenter registry assessing the outcomes and complications of MRgLITT among children. This study will answer the critical questions about the benefits and risks of this novel therapy for the treatment of drug-resistant epilepsy among children. We presented our preliminary data of MRgLITT among children at AES2020. Once data collection is completed, we will compare the outcomes of MRgLITT with those of surgery. 

NLN: What areas of future research are needed going forward for this treatment?

Dr Widjaja: Future studies assessing the long-term effectiveness of this treatment, as well as a health economic evaluation comparing the cost and effectiveness of MRgLITT vs surgery, are required to evaluate the value of this novel therapy.

NLN: What key takeaways do you hope to leave with neurologists and neurology providers?

Dr Widjaja: MRgLITT is a minimally invasive therapy that could achieve seizure freedom among more than half of children with focal drug-resistant epilepsy. Although the success of MRgLITT is slightly lower than that of surgery, it is generally well-tolerated because it is minimally invasive, requires shorter hospital stays, and has fewer permanent neurological deficits compared with surgery.

—Christina Vogt

Reference:
Yossofzai O, Stone S, Madsen J, et al. Outcomes of North American Pediatric Epilepsy MRI-guided Laser Interstitial Thermal Therapy (PEP-LITT) Registry. Paper presented at: American Epilepsy Society virtual meeting (AES2020); December 4-8, 2020.