Laser interstitial thermotherapy (LiTT) in epilepsy surgery

Abstract

Besides other innovative stereotactic procedures (radiofrequency thermocoagulation, focused ultrasound, gamma knife) laser interstitial thermotherapy (LiTT) provides minimally invasive destruction of pathological soft tissues which could be especially relevant for epilepsy surgeries involving adult and pediatric patients. Unlike standard resections, no craniotomy is required; just a tiny borehole trepanation is sufficient. Damage to cortical areas when accessing deep lesions can be minimized or completely avoided, and treating epileptogenic foci near eloquent or even vital brain areas becomes possible. Here, we briefly describe the history and rationale of laser neurosurgery as well as the technical key features of the two currently available systems for magnetic resonance-guided LiTT (Visualase, NeuroBlate; CE marks pending for both). We also discuss the published clinical experience with LiTT in the field of epilepsy surgery (approximately 200 cases) with regard to complications, LiTT-induced, long-term brain structural alterations, seizure outcome, preliminary neuropsychological findings and first estimates of treatment costs. Overall, the seizure outcome appears to be slightly worse than for resective surgery. Due to insufficient research methods (e.g. non-established measures, lack of a control condition), the expected neuropsychological superiority over resective surgery has not been unambiguously demonstrated thus far. Also, the cost-benefit ratio requires further critical evaluation. Clinical, multi-center and adequately controlled outcome studies of high quality should also accompany the imminent introduction of LiTT into the field of epilepsy surgery and therewith permit critical scientific evaluation and rational, individual, clinical decisions.

Laser ablation for mesial temporal lobe epilepsy: Surgical and cognitive outcomes with and without mesial temporal sclerosis

“…These outcomes are roughly comparable to traditional amygdalo‐hippocampectomies and anterior temporal lobe resections, and are better than previously published MRIgLITT case series . Compared to traditional anterior temporal resections, where Engel I surgical outcomes at 2 years of follow‐up is obtained for about 67% of patients, the Engel I surgical outcome obtained after MRIgLITT has been viewed as inferior by about 10%‐20% . Further, analyzing patients with a diagnosis of MTS and the necessity of SEEG investigations for seizure‐onset zone identification revealed no statistically significant differences between the percentages of patients with Engel class I surgical outcomes (Figure B).…”

“…A major advantage of the laser ablation approach in the treatment of MTLE, is the reduction of cognitive deficits, especially in the language‐dominant hemisphere . The surgical outcomes following MRIgLITT, as discussed in recent review articles, have been viewed as inferior to those of traditional anterior mesial resections, but this is considered a trade‐off for better postsurgery cognitive performance . We observed a decline in some aspects of memory: CVLT–II short delayed cued recall, immediate memory from the Logical Memory subtest of WMS–III) and expressive language (Verbal IQ subtest of WASI).…”

The immediate and short‐term effects of bilateral intrahippocampal depth electrodes on verbal memory

“…At our center, we therefore restricted implantations to 1 hippocampus whenever possible and later we changed to stereotactic implantations with lateral depth electrodes, placed orthogonally to the long axis of the hippocampus, thereby minimizing the potential hippocampal damage. However, the question remains how to implant patients for intracranial EEG ahead of hippocampal thermocoagulation …”

Automated trajectory planning for laser interstitial thermal therapy in mesial temporal lobe epilepsy

“…The majority of the clinical experience surrounding LiTT in epilepsy uses the Visualase system (Medtronic Inc., Minneapolis, MN, USA). The extent of the thermal ablation volume is monitored in real‐time with MR thermography . A critical part to the process, both in terms of safety and efficacy, involves the planning of the laser trajectory because this determines ablation safety, location, and volume.…”