Magnetic resonance image-guided laser interstitial thermal therapy for epilepsy
Authoritative guidelines
The American Society for Stereotactic and Functional Neurosurgery (ASSFN), which acts as the joint section representing the field of stereotactic and functional neurosurgery on behalf of the Congress of Neurological Surgeons and the American Association of Neurological Surgeons, provides an expert consensus opinion on evidence-based best practices for the use and implementation of this treatment modality. Indications for treatment are outlined, consisting of failure to respond to, or intolerance of, at least 2 appropriately chosen medications at appropriate doses for disabling, localization-related epilepsy in the setting of well-defined epileptogenic foci, or critical pathways of seizure propagation accessible by MRgLITT. Applications of MRgLITT in mesial temporal lobe epilepsy and hypothalamic hamartoma, along with its contraindications in the treatment of epilepsy, are discussed based on current evidence. To put this position statement in perspective, they detail the evidence and authority on which this ASSFN position statement is based 1).
Review
In 2013 a report includes an overview of the development and practice of an MR-guided laser ablation therapy known as MRI-guided laser interstitial thermal therapy (MRgLITT). The role of modern image-guided trajectory planning in MRgLITT will also be discussed, with particular emphasis on the treatment of refractory epilepsy using this novel, minimally invasive technique.
MRI-guided laser-induced thermal ablation for epilepsy is an exciting new minimally invasive technology that finds potential new applications every day in the neurosurgical field. It certainly brings a new perspective on the way we practice epilepsy surgery even though long-term results should be properly collected and analyzed 2).
Retrospective single-center cohort studies
Magnetic Resonance Imaging guided Laser Interstitial Thermal Therapy is a promising drug-resistant epilepsy treatment (DRE) and an alternative to open surgery. However, the relationship between clinical and radiological factors and postoperative outcomes is unclear. This study explores the indications, technical challenges, and outcomes of MRIgLITT in terms of seizure control and cognitive changes across various pathologies.
A retrospective single-center analysis included 32 MRIgLITT procedures performed between January 2019 and December 2023. Procedures used the Visualase® system for laser ablation, with stereotactic robotic guidance for fiber placement. Data included demographics, clinical and surgical details (ablated volume, timing, power and accuracy), and postoperative follow-up assessed seizure outcomes and complications. Cognitive changes were analyzed using a Reliable Change Index (RCI) before and one year after the procedure.
The 32 procedures involved 28 patients with MRI-diagnosed pathologies: 14 hippocampal sclerosis (HS), 7 hypothalamic hamartoma (HH), 3 focal cortical dysplasia (FCD), 2 periventricular heterotopia (PVH), 1 tuberous sclerosis complex (TSC), and 1 low-grade glioma. Some cases required multiple approaches. Postoperative follow-up averaged 33 months. Among HS patients, 71.42% achieved Engel I, and 21.43% Engel II. In HH, 85.7% initially became gelastic seizure-free, with complete freedom after additional treatment. Engel I outcomes were 28.6%, while 57.2% showed significant improvement (Engel I + II). FCD patients had a 66.6% Engel I success rate. One PVH patient became seizure-free, while the TSC patient was Engel III at last follow-up. RCI analysis showed that 71.44% of patients experienced cognitive stability (RCI > -1.64) or improvement (RCI > 1.64) at one-year post-procedure.
MRIgLITT is a safe, minimally invasive alternative for epilepsy surgery, offering quicker recovery and showing better performance preserving cognitive function. It is particularly effective for deep or complex epileptic focus and patients who might refuse open surgery 3).
Technical notes
Magnetic resonance thermography-guided laser interstitial thermal therapy (LITT) provides a minimally invasive treatment option in children with central nervous system tumors or medically intractable epilepsy. However, transporting anesthetized children between an operating room (OR) and a radiologic suite creates logistical challenges. Thus we describe advantages of using a 2-room intraoperative magnetic resonance imaging (MRI) concept for LITT.
Methods: Patients were pinned in a head frame that doubles as the lower part of the MRI head coil. Preoperative MRI was performed for accurate neuronavigation, after which laser fibers were stereotactically implanted. Transport between OR and MRI was achieved by sliding the top of the OR table onto a trolly.
Results: We performed 12 procedures in 11 children, mean age 7.1 years (range: 2 to 14 years). Ten children suffered from medically intractable epilepsy, and 1 child had a pilocytic midbrain astrocytoma. Two fibers were placed in 8 and 1 fiber in 4 procedures. Mean entry point and target errors were 2.8 mm and 3.4 mm, respectively. Average transfer time from OR to MRI and vice versa was 9 minutes (±1 minute, 40 seconds). Altogether, 50% of the seizure patients were seizure free (Engel grade I) at 22 months' follow-up time. One hemorrhagic event, which could be managed nonoperatively, occurred. We recorded no surgical site or intracranial infections.
Conclusions: All LITT procedures were successfully carried out with head frame in the sterile environment. The intraoperative MRI suite proved to be advantageous for minimally invasive procedures, especially in young children resulting in short transports while maintaining high accuracy and safety 4).