Laser Interstitial Thermal Therapy Research Articles

Patient-specific temperature distribution prediction in laser interstitial thermal therapy: single-irradiation data-driven method

Laser interstitial thermal therapy (LITT) is popular for treating brain tumours and epilepsy. The strict control of tissue thermal damage extent is crucial for LITT. Temperature prediction is useful for predicting thermal damage extent. Accurately predicting in vivo brain tissue temperature is challenging due to the temperature dependence and the individual variations in tissue properties. Considering these factors is essential for improving the temperature prediction accuracy. Objective. To present a method for predicting patient-specific tissue temperature distribution within a target lesion area in the brain during LITT. Approach. A magnetic resonance temperature imaging (MRTI) data-driven estimation model was constructed and combined with a modified Pennes bioheat transfer equation (PBHE) to predict patient-specific temperature distribution. In the PBHE for temperature prediction, the individual specificity and temperature dependence of thermal tissue properties and blood perfusion, as well as the individual specificity of optical tissue properties were considered. Only MRTI data during one laser irradiation were required in the method. This enables the prediction of patient-specific temperature distribution and the resulting thermal damage region for subsequent ablations. Main results. Patient-specific temperature prediction was evaluated based on clinical data acquired during LITT in the brain, using intraoperative MRTI data as the reference standard. Our method significantly improved the prediction performance of temperature distribution and thermal damage region. The average root mean square error was decreased by 69.54%, the average intraclass correlation coefficient was increased by 37.5%, the average Dice similarity coefficient was increased by 43.14% for thermal damage region prediction. Significance. The proposed method can predict temperature distribution and thermal damage region at an individual patient level during LITT, providing a promising approach to assist in patient-specific treatment planning for LITT in the brain.

Laser interstitial thermal therapy (LITT) for pediatric low-grade glioma-case presentations and lessons learned.

The surgical treatment of brain tumors has developed over time, offering customized strategies for patients and their specific lesions. One of the most recent advances in pediatric neuro-oncological surgery is laser interstitial thermal therapy (LITT). However, its effectiveness and indications are still being evaluated. The aim of this work is to review the current literature on LITT for pediatric low-grade gliomas (pLGG) and evaluate our initial results in this context. We retrospectively reviewed our pediatric neurosurgery database for patients who received LITT treatment between November 2019 and December 2023. We collected data on the indications for LITT, technical issues during the procedure, and clinical and radiological follow-up. Three patients underwent 5 LITT procedures for pLGG. The lesion was thalamo-peduncular in one patient, cingulate in one, and deep parietal in one patient. Two patients had a previous open resection done and were diagnosed with pLGG. One patient underwent a stereotaxic biopsy during the LITT procedure that was non-diagnostic. The same patient underwent a later open resection of the tumor in the cingulate gyrus. There were no surgical complications and all patients were discharged home on the first post-operative day. The follow-up period was between 20 and 40 months. Radiological follow-up showed a progressive reduction of the tumor in patients with LGG. Laser interstitial thermal therapy is a minimally invasive treatment that shows promise in treating deep-seated pLGG in children. The treatment has demonstrated a reduction in tumor volume, and the positive results continue over time. LITT can be used as an alternative treatment for tumors located in areas that are difficult to access surgically or in cases where other standard treatment options have failed.

Intraoperative changes in large-scale thalamic circuitry following laser ablation of hypothalamic hamartomas

Background and objectivesGelastic seizures due to hypothalamic hamartomas (HH) are challenging to treat, in part due to an incomplete understanding of seizure propagation pathways. Although magnetic resonance imaging-guided laser interstitial thermal therapy (MRgLITT) is a promising intervention to disconnect HH from ictal propagation networks, the optimal site of ablation to achieve seizure freedom is not known. In this study, we investigated intraoperative post-ablation changes in resting-state functional connectivity to identify large-scale networks associated with successful disconnection of HH. MethodsChildren who underwent MRgLITT for HH at two institutions were consecutively recruited and followed for a minimum of one year. Seizure freedom was defined as Engel score of 1A at the last available follow-up. Immediate pre- and post- ablation resting-state functional MRI scans were acquired while maintaining a constant depth of general anesthetic. Multivariable generalized linear models were used to identify intraoperative changes in large-scale connectivity associated with seizure outcomes. ResultsTwelve patients underwent MRgLITT for HH, five of whom were seizure-free at their last follow-up. Intraprocedural changes in thalamocortical circuitry involving the anterior cingulate cortex were associated with seizure-freedom. Children who were seizure-free demonstrated an increase and decrease in connectivity to the pregenual and dorsal anterior cingulate cortices, respectively. In addition, children who became seizure-free demonstrated increased thalamic connectivity to the periaqueductal gray immediately following MRgLITT. DiscussionSuccessful disconnection of HH is associated with intraoperative, large-scale changes in thalamocortical connectivity. These changes provide novel insights into the large-scale basis of gelastic seizures and may represent intraoperative biomarkers of treatment success.

Outcomes of stereoelectroencephalography following failed epilepsy surgery in children.

Stereoelectroencephalography (SEEG) is valuable for delineating the seizure onset zone (SOZ) in pharmacoresistant epilepsy when non-invasive presurgical techniques are inconclusive. Secondary epilepsy surgery after initial failure is challenging and there is limited research on SEEG following failed epilepsy surgery in children. The objective of this manuscript is to present the outcomes of children who underwent SEEG after failed epilepsy surgery. In this single-institution retrospective study, demographics, previous surgery data, SEEG characteristics, management, and follow-up were analyzed for pediatric patients who underwent SEEG after unsuccessful epilepsy surgery between August 2016 and February 2023. Fifty three patients underwent SEEG investigation during this period. Of this, 13 patients were identified who had unsuccessful initial epilepsy surgery (24%). Of these 13 patients, six patients (46%) experienced unsuccessful resective epilepsy surgery that targeted the temporal lobe, six patients (46%) underwent surgery involving the frontal lobe, and one patient (8%) had laser interstitial thermal therapy (LITT) of the right insula. SEEG in two thirds of patients (4/6) with initial failed temporal resections revealed expanded SOZ to include the insula. All 13 patients (100%) had a subsequent surgery after SEEG which was either LITT (54%) or surgical resection (46%). After the subsequent surgery, a favorable outcome (Engel class I/II) was achieved by eight patients (62%), while five patients experienced an unfavorable outcome (Engel class III/IV, 38%). Of the six patients with secondary surgical resection, four patients (67%) had favorable outcomes, while of the seven patients with LITT, two patients (29%) had favorable outcomes (Engel I/II). Average follow-up after the subsequent surgery was 37 months ±23 months. SEEG following initial failed resective epilepsy surgery may help guide next steps at identifying residual epileptogenic cortex and is associated with favorable seizure control outcomes.

The Impact of Perilesional Heatsink Structures on Ablation Volumes in Laser Interstitial Thermal Therapy for Brain Metastases

BACKGROUND AND OBJECTIVES: Laser interstitial thermal therapy (LITT) has demonstrated promise in surgical neuro-oncology because of its effectiveness in delivering precise thermal energy to lesions. The extent of ablation (EOA) is a prognostic factor in improving patient outcomes but is often affected by perilesional heatsink structures, which can lead to asymmetric ablations. The purpose of this study was to quantitatively evaluate the impact of various perilesional heatsink structures on the EOA in LITT for brain metastases. METHODS: Twenty-seven procedures for 22 unique patients with brain metastases fit the inclusion criteria. Intracranial heatsink structures were identified: sulci, meninges, cerebrospinal fluid (CSF) spaces, and vasculature. Asymmetric ablation was determined by measuring 3 pairs of orthogonal distances from the proximal, midpoint, and distal locations along the laser catheter to the farthest edge of the ablation zone bilaterally. Distances from the same points on the laser catheter to the nearest heatsink were also recorded. The Heatsink Effect Index was created to serve as a proxy for asymmetric ablation. Pearson correlations, t-tests, and analysis of variance were the statistical analyses performed. RESULTS: From the midpoint of the catheter, the 27 heatsinks were meninges (40.7%), sulci (22.2%), vasculature (22.2%), and CSF spaces (14.8%). Across all points along the catheter track, there was a significant generalized heatsink effect on asymmetric ablations (P < .0001). There was a negative correlation observed between asymmetric ablations and EOA from the midpoint of the laser catheter (r = −0.445, P = .020). Compared with sulci, CSF spaces trended toward a greater effect on asymmetric ablation volumes (P = .069). CONCLUSION: This novel quantitative analysis shows that perilesional heatsinks contribute to asymmetric ablations. CSF spaces trended toward higher degrees of asymmetric ablations. Importantly, neurosurgeons may anticipate asymmetric ablations preoperatively if heatsinks are located within 13.3 mm of the laser probe midpoint. These preliminary results may guide surgical decision-making in LITT for metastatic brain lesions.

Commentary: The Impact of Perilesional Heatsink Structures on Ablation Volumes in Laser Interstitial Thermal Therapy for Brain Metastases

Commentary: The Impact of Perilesional Heatsink Structures on Ablation Volumes in Laser Interstitial Thermal Therapy for Brain Metastases

Laser interstitial thermal therapy for recurrent glioblastomas: a systematic review and meta-analysis.

We aim to investigate the efficacy and safety of laser interstitial thermal therapy (LITT) in treating recurrent glioblastomas (rGBMs). A comprehensive search was conducted in four databases to identify studies published between January 2001 and June 2022 that reported prognosis information of rGBM patients treated with LITT as the primary therapy. The primary outcomes of interest were progression-free survival (PFS) and overall survival (OS) at 6 and 12 months after LITT intervention. Adverse events and complications were also evaluated. Eight eligible non-comparative studies comprising 128 patients were included in the analysis. Seven studies involving 120 patients provided data for the analysis of PFS. The pooled PFS rate at 6 months after LITT was 25% (95% CI 15-37%, I2 = 53%), and at 12 months, it was 9% (95% CI 4-15%, I2 = 24%). OS analysis was performed on 54 patients from six studies, with an OS rate of 92% (95% CI 84-100%, I2 = 0%) at 6 months and 42% (95% CI 13-73%, I2 = 67%) at 12 months after LITT. LITT demonstrates a favorable safety profile with low complication rates and promising tumor control and overall survival rates in patients with rGBMs. Tumor volume and performance status are important factors that may influence the effectiveness of LITT in selected patients. Additionally, the combination of LITT with immune-based therapy holds promise. Further well-designed clinical trials are needed to expand the application of LITT in glioma treatment.

Comparative analysis of bevacizumab and LITT for treating radiation necrosis in previously radiated CNS neoplasms: a systematic review and meta-analysis.

Radiation necrosis (RN) is a local inflammatory reaction that arises in response to radiation injury and may cause significant morbidity. This study aims to evaluate and compare the efficacy of bevacizumab and laser interstitial thermal therapy (LITT) in treating RN in patients with previously radiated central nervous system (CNS) neoplasms. PubMed, Cochrane, Scopus, and EMBASE databases were screened. Studies of patients with radiation necrosis from primary or secondary brain tumors were included. Indirect meta-analysis with random-effect modeling was performed to compare clinical and radiological outcomes. Twenty-four studies were included with 210 patients in the bevacizumab group and 337 patients in the LITT group. Bevacizumab demonstrated symptomatic improvement/stability in 87.7% of cases, radiological improvement/stability in 86.2%, and steroid wean-off in 45%. LITT exhibited symptomatic improvement/stability in 71.2%, radiological improvement/stability in 64.7%, and steroid wean-off in 62.4%. Comparative analysis revealed statistically significant differences favoring bevacizumab in symptomatic improvement/stability (p = 0.02), while no significant differences were observed in radiological improvement/stability (p = 0.27) or steroid wean-off (p = 0.90). The rates of adverse reactions were 11.2% for bevacizumab and 14.9% for LITT (p = 0.66), with the majority being grade 2 or lower (72.2% for bevacizumab and 62.5% for LITT). Both bevacizumab and LITT exhibited favorable clinical and radiological outcomes in managing RN. Bevacizumab was found to be associated with better symptomatic control compared to LITT. Patient-, diagnosis- and lesion-related factors should be considered when choosing the ideal treatment modality for RN to enhance overall patient outcomes.

Combinatorial Checkpoint Blockade and Laser Interstitial Thermal Therapy: A Single Center Study

INTRODUCTION: Immune checkpoint blockade (ICB) has gained acceptance as a life-extending therapy in a variety of solid tumor types. For patients with brain metastases, combination stereotactic radiosurgery (SRS) and ICB remains an area of clinical equipoise. Similarly, for recurrent or difficult-to-access intracranial lesions, safety and synergy of laser interstitial thermal therapy (LITT) and ICB has yet to be explored. METHODS: In accordance with an IRB-approved protocol, all patients undergoing LITT at a tertiary center from 2015-2022 were retrospectively reviewed. Patients who received ICB within 6 weeks of LITT were included in the LITT + ICB cohort. Demographic, clinical, and survival data were collected. RESULTS: Combination LITT and ICB occurred in 25 patients with clinically recurrent tumors. The median cohort age was 62 (40-78) and 12 (48%) were female. The median KPS was 80 (50-100). The most common primary pathology was non-small cell lung cancer (NSCLC) in 15 patients (60%), followed by melanoma in 3 (12%); two high-grade gliomas were additionally treated. The majority of the cohort (24 patients, 96%) recieved single agent ICB in combination with LITT, with pembrolizumab (12, 48%) and nivolumab (6, 24%) most common. Median duration between ICB dosing and LITT was 2.85 (0.85-5.84) weeks. Ten patients (40%) had evidence of immune-related adverse events attributable to ICB, with only 1 event > grade 3 according to Common Terminology Criteria; 17 (68%) had a pre-LITT steroid requirement. Intracranial adverse events related to LITT were rare, with median overall survival for the cohort of 8.6 months (1.4-26.4 months). CONCLUSIONS: Combination LITT and ICB appears safe and feasible. No prospective studies have compared cytoreduction with LITT to LITT + ICB; construction of a matched NSCLC cohort is ongoing. Exploration of the immune consequences of LITT + ICB is needed.

Treatment Plan Optimization Following Laser Interstitial Thermal Therapy (LITT) for Recurrent Metastasis Using Cleveland Clinic Scaling System (CCSS)

INTRODUCTION: Laser interstitial thermal therapy (LITT) is an effective treatment option for recurrent metastasis (RM). However, determining the best treatment approach for each patient following LITT remains challenging due to mixed pathology and lack of consensus. The Cleveland Clinic Scaling System (CCSS) has been proposed to facilitate decision-making in patients with radiation necrosis (RN) and/or RM following LITT. METHODS: We conducted a retrospective analysis of data from 20 patients who underwent LITT for RN and/or RM between 2019 and 2022 at Cleveland Clinic. Based on the symptomatic RN and/or RM which was confirmed by MRI, LITT, and biopsy were carried out. Three samples were acquired from the superficial, middle, and deep parts of each patient’s lesion. The samples were then classified into three main categories: RN, RM, or a mixture of the two, based on pathological results. Patient management was guided by our novel CCSS. According to CCSS, patients with 100% RN underwent continued observation with a 3-month MRI, individuals with >20% tumor component received a low-dose or standard-dose radiation therapy ± CNS-penetrating targeted therapy, while those with <20% tumor underwent short-term observation with 6-week MRIs ± CNS-penetrating targeted therapy. RESULTS: Among the patients, 57% were females, lung cancer was the most prevalent malignancy (61.4%), and the median age was 52 years (ranging from 25 to 83 years). Our analysis demonstrated that the application of the CCSS protocol significantly improved treatment outcomes after LITT, resulting in 93% lesion control at the 10-month follow-up. CONCLUSIONS: The use of the CCSS protocol can refine the treatment plan for patients with RN and/or RM following LITT. This approach has the potential to enhance patient safety by improving tumor control and minimizing unnecessary radiation.

204 Laster Interstitial Thermal Therapy for Primary and Recurrent Meningioma: A Prospective and Retrospective Multi-institutional Study

INTRODUCTION: Meningiomas are a common central nervous system tumor, and a subset are aggressive lesions resistant to standard therapies. Laser interstitial thermal therapy (LITT) has been successfully applied to other brain tumors, but its role in meningioma treatment is understudied. METHODS: Eight United States-based hospitals enrolled patients with meningioma in the prospective multicenter registry and pooled additional retrospective enrollments for this cohort study. Demographics, procedural, safety, and outcomes data were collected and analyzed using standard statistical methods. RESULTS: Twenty adult patients (12 prospective, 8 retrospective) with LITT-targeted meningiomas were accrued. Patients underwent LITT for primary (6 patients) and recurrent tumors (14 patients, ranging from 1st to 12th recurrence). Twenty percent of patients (4/20) had exhausted all other treatment options. Median length of follow-up was 1.3 years. One-third of primary (2/6) and one-half of recurrent meningiomas (7/14) recurred during follow-up. Of those with grading information, grade 2 meningiomas were most common (9/18), followed by Grade 1(5/18), and Grade 3 (4/18). Sixty percent (60%) of patients (12/20) had convexity meningiomas treated with LITT. 2 patients (10%) had post-procedural complications, of which one resolved. One-year estimated local control (LC), progression-free survival, and overall survival were 55.3%, 48.4%, and 86.3%, respectively. In the 10 patients who had 91% ablative coverage, 1-year estimated LC was 64.8%. High grade (Grades 2 and 3) patients (n = 13) treated with LITT had a 1-year LC of 46.3%. CONCLUSIONS: This cohort represents the largest series of patients with meningioma undergoing LITT and supports the safety of the procedure in this tumor type. LITT can offer a much-needed treatment option, especially for those with multiply recurrent meningiomas and where heavy pretreatment limits remaining treatment options. LITT should be considered in the armamentarium of treatment options for meningiomas.

376 Laser Interstitial Thermal Therapy for Deep-Seated Perivascular Brain Tumors: Evaluating the Risk of Distal Ischemia

INTRODUCTION: Laser interstitial thermal therapy (LITT) is a novel minimally invasive cytoreductive treatment option for primary and metastatic brain tumors. By relying on stereotactic guidance, the use of LITT carries a risk for direct and thermal vascular injury, especially when targeting deep-seated tumors with surrounding critical vasculature. It is thought that nearby blood vessels act as heat sinks from thermal injury, however, the risk of ablation causing an ischemic stroke is not well reported. METHODS: A retrospective review identified patients who underwent LITT between 2013 – 2021 for brain tumors located within the insula, basal ganglia, and thalamus. Demographic, clinical, and volumetric characteristics were collected. The primary outcome was radiographic evidence of distal ischemia on post-ablation imaging. RESULTS: A total of 50 patients underwent 59 ablations for perivascular brain tumors located in the insula (52%), basal ganglia (24%), and thalamus (24%). Of the tumors treated, 22 (37%) were low-grade gliomas, 32 (54%) were high-grade gliomas, and 5 (8%) were metastatic. No coagulopathies were identified in any patient. A biopsy was performed in 72% of patients. The mean volume of ablation was 12.4 cm3 (S.D. 13.9) with a median extent of ablation of 92% (IQR 30%, 100%). Two patients developed symptomatic intracerebral hemorrhage. One developed a tract hemorrhage attributed to vessel injury from fiber insertion. The other presented with delayed onset hemorrhage one week later due to uncontrolled hypertension. In all patients, there was no radiographic evidence of distal ischemia following LITT on DWI sequencing . The median length of stay was 2 days with 81% of patients being discharged home. CONCLUSIONS: We demonstrate that LITT has minimal risk for new onset distal ischemia for deep-seated perivascular brain tumors.

497 Superficial MRI-guided Laser Interstitial Thermal Therapy (LITT) for Intracranial Metastasis Is Associated With a Significantly Higher Rate of Leptomeningeal Disease

INTRODUCTION: Evolving brain metastases treatment standards has led to shifting intracranial recurrence patterns, especially with respect to pachymeningeal and leptomeningeal disease (PMD/LMD). As an emerging technique, it remains unclear if the depth of magnetic resonance imaging-guided laser interstitial thermal therapy (LITT) is associated with frequency of iatrogenic PMD/LMD. METHODS: A single-institute retrospective analysis of patients who underwent LITT surgery between 2014 and 2022 was conducted to investigate the development of PMD/LMD. P-values <0.05 were considered statistically significant. RESULTS: Eleven patients undergoing thirteen LITT procedures were analyzed. Mean age was 62.6 (±11.7), and 69.2% of patients were female. PMD/LMD developed in 4/13 cases (30.8%). There was no significant difference between superficial vs. deep LITT ablation in terms of age, sex, follow-up time, and primary cancer site. Superficial LITT ablation had a significantly higher frequency of PMD/LMD compared to deep LITT ablation (p = 0.02). Time to PMD/LMD development among patients who underwent superficial LITT ablation was significantly shorter compared to that among patients who had deep LITT ablation (p = 0.02). CONCLUSIONS: Superficial LITT ablation was associated with significantly higher frequency and shorter time to PMD/LMD development compared to deep LITT ablation. These results suggest that iatrogenic PMD/LMD spread during superficial LITT ablation may increase the proportion of PMD/LMD and accelerate disease timeline.

1248 Optimal Connectivity Map Predicts Seizure Freedom Rates After Laser Interstitial Thermal Therapy in Mesial Temporal Lobe Epilepsy

INTRODUCTION: Laser Interstitial Thermal Therapy (LiTT) is increasingly becoming a first-line surgical therapy for mesial temporal lobe epilepsy (mTLE). While promising, its seizure outcomes have also been highly variable, presumably due to an incomplete understanding of mechanisms behind LiTT. Epilepsy is a network disorder, and therefore it is crucial to account for both the effect on local destruction of epileptogenic foci, as well as global intervention of limbic circuitry, to elucidate the circuit-level mechanisms of LiTT and devise improved ablation strategies. In this study, we explore LiTT's network-level effect by investigating functional connectivity patterns and identifying optimal connectivity patterns predictive of seizure freedom. METHODS: 27 mTLE patients who underwent unilateral LiTT were classified as seizure-free (ILAE Class I) or seizure-present (ILAE Class II–VI) cohort based on one-year postoperative outcomes. Individual ablation volumes were segmented from intraoperative MRI sequences. Ablation volumes were seeded into a normative functional connectome (Brain Genomics Superstruct Project) to extract patient-specific connectivity profiles associated with ablation volumes. FC patterns were compared between the two cohorts to produce voxel-wise “t-maps” to identify local and global differences in connectivity strengths predictive of seizure freedom. RESULTS: Ten mTLE patients achieved complete seizure freedom. In seizure-free patients, right ablated volumes shared higher FC with regions such as calcarine, cuneus, and thalamic anterior pulvinar nucleus than patients with seizure presence. CONCLUSIONS: For the right-sided ablations, seizure freedom was associated with a distinctive whole-brain connectivity pattern beyond the local surgical target. Further investigation is required to explore if this pattern is specific between the two surgical sides in mTLE population.

488 National Trends in the Treatment of Refractory Epilepsy: A Nationwide Inpatient SampleBased Propensity Score Matching Analysis

INTRODUCTION: Epilepsy is considered one of the most prevalent and severe chronic neurological disorders worldwide. METHODS: Using the NIS database from 2010-2020, patients with focal intractable epilepsy who underwent Laser Interstitial Thermal Therapy (LITT), open surgical resection, Vagal Nerve Stimulation (VNS), or Responsive Neuro-Stimulation (RNS) were identified. Outcomes such as discharge disposition, length of stay, complications, and mortality were analyzed. Propensity score matching was used to compare outcomes between pre-pandemic and pandemic (first peak of COVID-19) periods. RESULTS: A total of 33,969 focal intractable epilepsy cases were found with 3,343 patients receiving different treatment modalities including surgical resection (77.83%), VNS (8.21%), RNS (7.83%), and LITT (6.13%). Most of these patients (89.32%) were treated during the pre-COVID pandemic era (2010-2019), while a minority (10.67%) underwent treatment during the COVID pandemic (2020). Among all treated patients, 2.7% had postoperative neurologic complications and 0.3% died. After propensity-score matching, 658 patients (329 in each group) were included. During the pandemic period, 7% presented with preoperative paralysis/aphasia, and 0.6% had subarachnoid hemorrhages, which was significantly higher than the pre-pandemic rate (1.8%; p < 0.001). There were no statistical differences in neurologic complications, discharge disposition, or LOS between the pre-pandemic and pandemic periods. On the other hand, the mortality rate was slightly higher during the pandemic compared to the pre-pandemic period (N = 4; 1.2% vs. N = 1; 0.2%; p = 0.026). CONCLUSIONS: Our study shows an increase in the diagnosis of focal intractable epilepsy and a decrease in resections, while LITT and RNS usage is rising. Improving access to surgery and encouraging newer treatment modalities for DRE is crucial. Further research is needed to optimize patient outcomes and identify factors that influence treatment choices.

1229 Leveraging Machine Learning for Pre-operative Prediction of Supralesional Ablation in Laser Interstitial Thermal Therapy (LITT) for Brain Tumors

INTRODUCTION: Although maximizing the extent of ablation (EOA) following laser interstitial thermal therapy (LITT) can improve outcomes in patients with brain tumors, the pre-operative factors that predict a supralesional ablation (EOA >100%) remain unclear. METHODS: A retrospective study of patients with glioblastoma, metastasis, or radiation necrosis receiving LITT at a tertiary care referral center between 2013 to 2023 was conducted. Using the EOA >100% as a primary outcome, several clinical and radiographic pre-operative factors were evaluated. Five ML models, Decision Trees, Random Forest, Gradient Boosting, XGBoost, and AdaBoost, were trained using an 80/20 training/testing split and 5-fold cross validation. The models were optimized using hyperparameter tuning and evaluated against traditional logistic regression. The area under the receiver operating characteristic curve (AUC-ROC) was used to evaluate model performance. The optimal pre-operative volume cutoff for constituting an EOA >100% was also explored. RESULTS: 201 patients were included in the final cohort. Multivariate logistic regression showed that lower pre-operative volume (p < 0.001) and deep-seated lesions (p = 0.041) have a greater likelihood to undergo a supralesional ablation. Of the five ML models analyzed, Random Forest had the highest F1-score of 0.889, and XGBoost had the highest AUC-ROC of 0.74. Additionally, Random Forest (p = 0.02), Gradient Boosting (p < 0.001) and XGBoost (p = 0.01) showed statistically improved predictive performance compared to logistic regression. Features of importance were pre-operative volume, deep-seated lesions, and ellipsoid ratio. The pre-operative lesion volume cutoff for achieving an EOA >100% was 4.38 cc. CONCLUSIONS: This study shows the improved predictive ability of ML models over a traditional regression model in determining pre-operative factors for a supralesional ablation of brain tumors following LITT. Notably, the ML models identified pre-operative tumor volume, deep-seated tumors, and ellipsoid tumors as important factors, which could optimize treatment decisions and patient outcomes.

924 Corpus Callosotomy for Intractable Epilepsy: A Contemporary Series of Operative Factors and Overall Complication Rate

INTRODUCTION: Corpus callosotomy is an effective treatment for atonic seizures in medically refractory epilepsy. Recently, laser interstitial thermal therapy has been adapted as a less invasive method to achieve similar results, yet technical challenges associated with this nascent approach persist. A modern series of corpus callosotomies performed by open craniotomy is lacking in the literature, a fact which highlights the importance of establishing contemporary complication rates for this operation to compare with newer methodologies. METHODS: We retrospectively reviewed institutional data for patients who underwent first time open callosotomy from 2005 to 2022. Demographic and clinical variables were collected and analyzed with a focus on operative factors and complication rates. RESULTS: 105 patients were included in the study with a mean age of 9.39 years (0.67-24.17 years). 58.1% of patients were male (61), and one surgeon performed a majority (76.20%, 80) of the operations with two other surgeons performing the remainder (21.9% and 1.90%, respectively). In total, 63 complete, 31 subtotal (anterior 70-99%), and 1 posterior (40%) callosotomies were performed. Blood loss was available for 102/105 patients with a mean of 96.67 mL (10-500 mL), and mean operative time was calculated as 226.76 minutes (45-504 minutes) from 76/105 patients by excluding those patients who underwent concurrent vagal nerve stimulator placement or revision. Operative complication rate was determined to be 6.67% and was comprised of 3 pseudomeningoceles, 3 superficial wound infections, and 1 delayed intraparenchymal hemorrhage. No venous infarcts were observed on postoperative MRI. CONCLUSIONS: This the largest single center series of open callosotomy patients describes important updated metrics to help evaluate new techniques being developed for the surgical treatment of atonic seizures in medically intractable epilepsy.

Temporo-Parieto-Occipital Disconnection by Robot-Assisted Magnetic Resonance Imaging–Guided Laser Interstitial Thermal Therapy for Refractory Epilepsy in a Pediatric Patient: Proof-of-Principle Case Report and Surgical Nuances

Magnetic resonance imaging-guided laser interstitial thermal therapy (MRIgLITT) has been proven safe and effective for the treatment of focal epilepsy of different etiologies. It has also been used to disconnect brain tissue in more extensive or diffuse epilepsy, such as corpus callosotomy and hemispherotomy. In this study, we report a case of temporo-parieto-occipital disconnection (TPO) surgery performed using MRIgLITT assisted by a robotic arm for refractory epilepsy of the posterior quadrant. A highly realistic cadaver simulation was performed before the actual surgery. The patient was a 14-year-old boy whose seizures began at the age of eight. The epilepsy was a result of a left perinatal ischemic event that caused a porencephalic cyst, and despite receiving multiple antiepileptic drugs, the patient continued to experience daily seizures which led to the recommendation of surgery. A Wada test lateralized language in the right hemisphere. Motor and sensory function was confirmed in the left hemisphere through MRI functional studies and NexStim®. The left MRIgLITT TPO disconnection was achieved using five laser fibers. The patient followed an excellent postoperative course and was seizure-free, with no additional neurological deficits 24 months after the surgery.

Impact of Previous Surgery on Success of Magnetic Resonance-guided Laser Interstitial Thermal Therapy (MRgLITT) to Treat Pediatric Epilepsy: An Institutional Experience

There is an emerging role for minimally invasive magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) in the treatment of pediatric epilepsy refractory to medication. To date, predictors of MRgLITT success have not been established in a sizeable singular experience. Correspondingly the aim of this study was to elucidate if previous surgical history predicts MRgLITT success in this setting. A retrospective review was conducted of our MRgLITT procedures for pediatric (aged <19 years) epilepsy from 2011-2020 with documented seizure outcomes at 1- and 2-years after procedure. Categorical and continuous data were compared using Chi-squared and student's t-test respectively. A total of 41 patients satisfied all criteria with 16 (39%) females and 25 (61%) males. Following MRgLITT, seizure-freedom at 1-year was achieved in 15 (37%) patients. In the cohort, there were 14 (34%) patients who had undergone previous open surgery for epilepsy at mean age of 9.4 ± 5.5 years. Patients with a previous open surgery history were found to statistically experience longer length of hospitalization after MRgLITT (P=0.04) with a statistically lower proportion of seizure-freedom at 1-year after MRgLITT (14% vs 48%, P=0.03). However, there was no difference in the rate of seizure-freedom at 2-years (29% vs 41%, P=0.44), as well as no difference in subsequent surgical interventions for seizure management between groups. Based on our institutional experience, patients with previous open surgery history may experience longer length of hospitalization after MRgLITT for pediatric epilepsy and lesser response in seizure-freedom within the first year but with non-inferior seizure-freedom by the second year.

Unilateral Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy Thalamotomy for Essential Tremor.

Essential tremor (ET) affects numerous adults, impacting quality of life (QOL) and often defying pharmacological treatment. Surgical interventions like deep brain stimulation (DBS) and lesional approaches, including radiofrequency, gamma-knife radiosurgery, and magnetic resonance imaging (MRI)-guided focused ultrasound, offer solutions but are not devoid of limitations. This retrospective, single-center, single-blinded pilot study aimed to assess the safety and efficacy of unilateral MRI-guided laser interstitial thermal therapy (MRIg-LITT) thalamotomy for medically intractable ET. Nine patients with ET, unresponsive to medications and unsuitable for DBS, underwent unilateral MRIg-LITT thalamotomy. We assessed tremor severity, QOL, cognitive function, and adverse events (AE) over a 12-month period. Tremor severity significantly improved, with a reduction of 83.37% at 12 months post-procedure. QOL scores improved by 74.60% at 12 months. Reported AEs predominantly included transient dysarthria, proprioceptive disturbances, and gait balance issues, which largely resolved within a month. At 3 months, 2 patients (22%) exhibited contralateral hemiparesis requiring physiotherapy, with 1 patient (11%) exhibiting persistent hemiparesis at 12 months. No significant cognitive impairment was detected post-procedure. Unilateral MRIg-LITT thalamotomy yielded substantial and enduring tremor alleviation and enhanced QOL in patients with ET that is resistant to medication. The AE profile was acceptable. Our findings support the need for additional research with expanded patient cohorts and extended follow-up to corroborate these outcomes and to refine the role of MRIg-LITT as a targeted and minimally invasive approach for ET management. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.