MR-guided laser interstitial thermal therapy (MRgLITT) has emerged as a safe and effective treatment option for the ablation of epileptic foci. Its minimally invasive nature makes it attractive due to decreased morbidity and hospital stay.
Magnetic resonance guided laser induced thermal therapy for epilepsy is an exciting new minimally invasive technique 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 1).
The report of Willie et al., demonstrates the technical feasibility and encouraging early results of stereotactic laser amygdalohippocampotomy (SLAH), a novel approach to eliminating seizures while minimizing collateral injury in patients with MTLE. Efficacy appears to approach that of open resection, especially in patients with MTS. Such minimally invasive techniques may be more desirable to patients and result in increased use of epilepsy surgery among the large number of medically intractable epilepsy patients. A larger, longer term multicenter study of seizure and cognitive outcomes after SLAH is currently under way 2).
Treatment of medication-resistant epilepsy that accomplishes ablation of the seizure focus with real-time magnetic resonance thermal mapping. Rates of seizure freedom in early series suggest that SLA approaches and perhaps surpasses the effectiveness of open resection. SLA minimizes the neurocognitive and endocrine adverse effects of open surgery. Secondary benefits of SLA include decreased length of stay, elimination of intensive care unit stay, reduced procedure-related discomfort, and improved access to surgical treatment for patients less likely to consider an open resective procedure 3).
A retrospective review of patients who underwent MRgLITT via Visualase laser ablation at Department of Neurosurgery, MedStar Georgetown University Hospital, Children's National Medical Center, Washington, USA was performed. Demographic and outcome data were compiled and analyzed.
Twelve pediatric patients with a total 18 lesions underwent MRgLITT procedures between December 2013 and September 2017. Mean age at surgery was 11.1 years. Surgical substrates included 4 hypothalamic hamartomas, 3 periventricular heterotopias, 2 deep focal cortical dysplasias, 2 tuberous sclerosis, and 1 mesial temporal sclerosis. Methods of stereotaxy used included Leksell frame, BrainLab VarioGuide, ROSA robot guidance, and ClearPoint navigation. Mean procedure length was 250 min, and mean length of stay was 1.3 days. After treatment, 8 patients were seizure free (Engel I, 66.7%), 2 patients demonstrated significant improvement (Engel II, 16.7%), and 2 patients showed worthwhile improvement (Engel III, 16.7%). One patient developed a left superior quadrantanopsia postoperatively. Mean follow-up duration was 10 months.
This study contributes to the sparse literature in this field by demonstrating the high efficacy and low morbidity of MRgLITT as a minimally invasive method of ablation of epileptic foci in the pediatric population of medically refractory lesional epilepsy 4).
Between October 2014 and May 2016, 17 patients with mesial temporal sclerosis were selected by a multidisciplinary epilepsy board to undergo a selective amygdalohippocampal ablation for temporal lobe epilepsy using MRgLITT. The first 9 patients underwent standard laser ablation in 2 phases (operating room [OR] and MRI suite), whereas the next 8 patients underwent laser ablation entirely in the MRI suite with the ClearPoint platform. A checklist specific to the real-time MRI-guided laser amydalohippocampal ablation was developed and used for each case. For both cohorts, clinical and operative information, including average case times and accuracy data, was collected and analyzed. RESULTS There was a learning curve associated with using this real-time MRI-guided system. However, operative times decreased in a linear fashion, as did total anesthesia time. In fact, the total mean patient procedure time was less in the MRI cohort (362.8 ± 86.6 minutes) than in the OR cohort (456.9 ± 80.7 minutes). The mean anesthesia time was significantly shorter in the MRI cohort (327.2 ± 79.9 minutes) than in the OR cohort (435.8 ± 78.4 minutes, p = 0.02). CONCLUSIONS The real-time MRI platform for MRgLITT can be adopted in an expedient manner. Completion of MRgLITT entirely in the MRI suite may lead to significant advantages in procedural times 5).
Five patients with medically refractory epilepsy undergoing standard presurgical evaluation were found to have corresponding lesions fulfilling imaging characteristics of CCM and were prospectively enrolled. Each underwent stereotactic placement of a saline-cooled cannula containing an optical fiber to deliver 980-nm diode laser energy via twist drill craniostomy. MR anatomic imaging was used to evaluate targeting prior to ablation. MR imaging provided evaluation of targeting and near real-time feedback regarding extent of tissue thermocoagulation. Patients maintained seizure diaries, and remote imaging (6-21 months post-ablation) was obtained in all patients.
Imaging revealed no evidence of acute hemorrhage following fiber placement within presumed CCM. MRT during treatment and immediate post-procedure imaging confirmed desired extent of ablation. We identified no adverse events or neurological deficits. Four of 5 (80%) patients achieved freedom from disabling seizures after SLA alone (Engel class 1 outcome), with follow-up ranging 12-28 months. Reimaging of all subjects (6-21 months) indicated lesion diminution with surrounding liquefactive necrosis, consistent with the surgical goal of extended lesionotomy 6).
A novel technique is presented for the application of MRgLITT in a 6-month-old infant for the treatment of epilepsy associated with tuberous sclerosis complex (TSC) .
To Hooten et al. knowledge this is the youngest patient treated with laser ablation. They used a frameless navigation technique with a miniframe tripod system and intraoperative reference points. This technique expands the application of MRgLITT to younger patients, which may lead to safer surgical interventions and improved outcomes for these children 7).