Laser Interstitial Thermal Therapy Procedures Research Articles

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.

Laser interstitial thermal therapy for first-line treatment of insular glioma.

Insular gliomas pose a significant surgical challenge due to the complex surrounding functional and vascular anatomy. The authors report their experience using a novel framework for the treatment of insular gliomas with laser interstitial thermal therapy (LITT) and provide representative case examples emphasizing indications, rationale, and technical pearls. A prospectively gathered institutional database was used to identify patients with newly diagnosed insular gliomas who underwent LITT between 2015 and 2023. The proposed framework of insular glioma management is guided by tumor size and extent of extra-insular tumor involvement. Patients with tumors localized to the insula (insula-only) were treated with single-session or staged LITT. Patients with insular tumors with frontotemporal involvement (insular+) were treated with insular LITT and standard frontotemporal resection of extra-insular tumor. Clinical and volumetric lesional characteristics were analyzed, with particular emphasis on extent of cytoreductive treatment and safety. Of the 261 patients treated at the authors' institution with LITT between 2015 and 2023, 33 LITT procedures were identified involving 22 unique patients with treatment-naive insular gliomas. Of the 22 patients, 12 had insular-only tumors and were treated with LITT alone, while 10 patients had insular+ lesions and were treated with LITT and resection. The median tumor volume for insular-only tumors was 13.4 cm3 (IQR 10.6, 26.3 cm3), with a median extent of treatment of 100% (IQR 92.1%, 100%). Insular+ lesions were significantly larger, with a median volume of 81.2 cm3 (IQR 51.9, 97 cm3) and median extent of treatment of 96.6% (IQR 93.7%, 100%). All patients with insular-only tumors were discharged the day after ablation, while insular+ patients had significantly longer hospital stays, with 50% staying more than 3 days. Overall, 8% of insular-only patients had permanent neurological deficits compared with 33% of insular+ patients. Two patients' tumors progressed during follow-up: one patient with WHO grade 4 astrocytoma and the other with diffuse glioma not otherwise specified. Patients with grade 4 tumors had the highest rate of permanent neurological deficit (43%) and a larger decline in postoperative Karnofsky Performance Status score (p = 0.046). The authors present their experience using a novel insular glioma treatment paradigm that incorporates LITT into the broader framework of insular glioma surgery. Their findings suggest that insular LITT is feasible and may allow for high rates of cytoreduction while potentially ameliorating the risks of conventional insular glioma surgery.

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.

High-Value Epilepsy Care in the United States: Predictors of Increased Costs and Complications from the National Inpatient Sample Database 2016–2019

IntroductionFor patients with medically refractory epilepsy newer minimally invasive techniques such as Laser Interstitial Thermal Therapy (LITT) have been developed in recent years. This study aims to characterize trends in the utilization of surgical resection versus LITT to treat medically refractory epilepsy, characterize complications, and understand the cost of this innovative technique to the public. MethodsThe National Inpatient Sample (NIS) database was queried from 2016 to 2019 for all patients admitted with a diagnosis of medically refractory epilepsy. Patient demographics, hospital length of stay, complications, and costs were tabulated for all patients who underwent LITT or surgical resection within these cohorts. ResultsA total of 6,019 patients were included, 223 underwent LITT procedures while 5,796 underwent resection. Significant predictors of increased patient charges for both cohorts included diabetes (OR 1.7, CI 1.44-2.19), infection (OR 5.12, CI 2.73-9.58), and hemorrhage (OR 2.95, CI 2.04-4.12). Procedures performed at non-teaching hospitals had 1.54 greater odds (CI 1.02-2.33) of resulting in a complication compared to teaching hospitals. Insurance status did significantly differ (p=0.001) between those receiving LITT (23.3% Medicare; 25.6% Medicaid; 44.4% Private insurance; 6.7 Other) and those undergoing resection (35.3% Medicare; 22.5% Medicaid; 34.7% Private Insurance; 7.5% other). When adjusting for patient demographics, LITT patients had shorter length of stay (2.3 vs 8.9 days, p < 0.001), lower complication rate (1.9% vs 3.1%, p=0.385), and lower mean hospital ($139,412.79 vs $233,120.99, p < 0.001) and patient ($55,394.34 vs $37,756.66, p < 0.001) costs. ConclusionThe present study highlights LITT’s advantages through its association with lower costs and shorter length of stay. The present study also highlights the associated predictors of LITT vs resection, such as that most LITT cases happen at academic centers for patients with private insurance. As the adoption of LITT continues, more data will become available to further understand these issues.

Laser Interstitial Thermal Therapy (LITT) for Neurosurgical Procedures: Facts You Need to Know About the Anesthetic Management of LITT Procedures.

The field of medicine is constantly advancing to improve patient care. As physicians, we must improve our knowledge by listening, reading, and practicing evidence-based medicine. Laser treatment has evolved over the years in many surgical specialties. Laser interstitial thermal therapy (LITT), also known as stereotactic laser ablation (SLA), was developed in neurosurgical procedures to treat recurrent or metastatic brain tumors, radiation necrosis, and epilepsy lesions. LITT procedures are advantageous in providing better patient outcomes, decreased hospital length of stay, and reduced total hospital cost. These procedures are performed as a multi-disciplinary approach; this article discusses the different types of LITT systems, indications, contraindications, types of anesthesia, perioperative anesthetic management,safety precautions, complications, recovery during and after LITT procedures, and the future of LITT procedures.

SURG-06. DEVELOPING A LASER INTERSTITIAL THERMAL THERAPY (LITT) PLATFORM FOR THE TREATMENT OF INTRACRANIAL LESIONS IN CANINES

Abstract Malignant gliomas are devastating intracranial tumors with dismal prognoses that impose unique therapeutic challenges. Treatment options include surgical resection, radiation, and chemotherapy, but efficacy is limited and carries associated morbidity. Promise persists for newer modalities, such as immune-based platforms, but obstacles include limited therapeutic access due to the blood-brain barrier (BBB) and the highly immunosuppressive tumor microenvironment. Laser interstitial thermal therapy (LITT) is a minimally invasive surgical intervention permitting thermal ablation of intracranial tumors. During LITT, a laser probe is stereotactically placed in the lesion through a skull burr hole. Real-time MRI is used to calculate thermal dosage zones to monitor ablation progress. LITT is not only cytoreductive but also opens the BBB and induces a powerful hyperthermia-driven anti-tumor immune response; it thus may synergize with other emerging therapies. Spontaneous canine glioma offers a matchless, optimally recapitulative appropriately sized tumor model, providing a unique opportunity to investigate and optimize the LITT platform. We adapted a commercially available LITT system (Monteris Medical) for application in canines with intracranial lesions. Initially, canine cadavers were used to optimize LITT procedures; we then performed LITT in live dogs. Our approach consists of 1. obtaining volumetric MRI studies for trajectory planning, 2. fixing canine patients to the surgical bed, 3. registering anatomic landmarks (Brainlab) to a volume rendered image, 4. using an integrated instrument holder (Varioguide, Brainlab) to guide drilling of 4.5 mm skull burr holes for placement of self-tapping titanium “mini-bolts” (Monteris Medical), and 5. introducing the laser through the mini-bolts for ablation in the MRI suite. This method allows for rigid stereotaxy, successful neuronavigation, and a minimally invasive approach. We have successfully performed LITT on four canine patients with intracranial gliomas. Future studies will explore immunologic mechanisms underlying the post-LITT anti-tumor response as well as combination therapeutic platforms, including nanoparticles and stereotactic radiotherapy.

MODL-14. IMAGING, HISTOLOGICAL AND MOLECULAR CHARACTERIZATION AND COMPARISON OF POST-ABLATION RECURRENT TUMOR WITH THE PRIMARY TUMOR IN A PRECLINICAL GLIOBLASTOMA MODEL

Abstract Recurrent glioblastoma (rGBM) is highly aggressive and invasive. A reliable preclinical model that recapitulates these features is not presently available. The objective was to generate a preclinical rGBM model, characterize and compare its imaging, histological and molecular signatures in comparison to the primary tumor. Immune-suppressed, RNU/RNU female rats were implanted with U251N tumor cells in one brain hemisphere (n=33). Tumor progression in all rats was followed by longitudinal dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI). In 24 rats the tumor was ablated under diffusion-weighted imaging (DWI)-guided laser interstitial thermal therapy (LITT) at post-implantation 2-weeks. Cohorts from twenty ablated rats were euthanized at post-LITT 24 h, 2- and 4-weeks and, along with 5 unablated controls, used for hematoxylin and eosin (H&amp;E) and Ki67 staining. Tissues from 4 other unablated and 4 recurrent tumors at post-LITT 2-weeks were used for RNAseq. All the rats survived the LITT procedure. Unablated controls showed increased tumor burden by post-implantation 2 weeks and were euthanized. In the LITT group, MRI showed little tumor tissue at 24 h, evidence of recurrence at 2 weeks and significant tumor tissue at 4 weeks and matched with histological evidence for tumor recurrence. Compared to the primary tumor, H&amp;E staining showed increased vascular hyperplasia, mitotic bodies and hypoxic regions with pseudopalisading necrosis in the recurrent tumor. Increased KI67 staining in recurrent tumors suggested higher rates of proliferation and evidence of infiltration into host tissue. Pathway analyses demonstrated differentially expressed genes in the canonical pathways of hypoxia-inducible factor-alpha (HIF-1α), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and OX40 signaling. The genes for the following functions were significantly affected: cell cycle, cellular movement and cell morphology. Reliable preclinical rGBM models are few. These data suggest that this model replicates the features of human rGBM and can be useful in testing putative anti-glioma therapies.

Laser interstitial thermal therapy compared with open resection for treating subependymal giant cell astrocytoma.

Subependymal giant cell astrocytomas (SEGAs) are WHO grade 1 tumors associated with tuberous sclerosis that classically arise from the ventricular wall near the caudate groove and foramen of Monro. Laser interstitial thermal therapy (LITT) is a minimally invasive surgical technique, which works by heating a stereotactically placed laser fiber to ablative temperatures under MRI thermometry monitoring. In this paper, the authors present LITT as a surgical alternative to open resection of SEGAs. Twelve patients with SEGAs who underwent 16 procedures between 2007 and 2022 at a single institution were retrospectively reviewed. These patients underwent either open resection or LITT. Clinical data, imaging, recurrence rate, further treatments, and related complications were analyzed. Among the 16 procedures, 9 were open resection and 7 were LITT. An external ventricular drain was placed in 66% (6/9) of open procedures and 57.1% (4/7) of LITT cases. A septostomy was performed in 56% (5/9) of open procedures and 29% (2/7) of LITT cases. Complication rates were higher in open cases than in LITT procedures (44% vs 0%, p < 0.05). Complications included hydrocephalus, transient venous ischemia, wound infection, and bone flap migration. The median length of hospital stay was 4 days (IQR 3.3-5.5 days) for open cases and 4 days (IQR 3.0-7.0 days) for LITT procedures. Recurrence or progression occurred after 3 open cases and 2 LITT cases (33% vs 33%, p = 0.803). For the recurrences, 2 open cases underwent stereotactic radiosurgery, 1 open case underwent LITT, and 1 LITT case underwent repeat LITT. Among the LITT cases, only the patients with no decrease in tumor size by 6 months experienced tumor progression afterward. The 2 LITT cases with progression were the only ones with calcification present on preoperative imaging. The median follow-up times for cases assessed for progression were 8.4 years (IQR 3.8-14.4 years) for open resection and 3.9 years (IQR 3.4-5.1 years) for LITT. The small size of this case series limits generalizability or adequate comparison of safety. However, this series adds to the literature supporting LITT as a less invasive surgical alternative to open resection of SEGAs and demonstrates that LITT has similar recurrence and/or progression rates to open resection. Additional studies with more data are necessary for comprehensive comparisons between open resection and LITT for treating SEGA.

Development of a Treatment Planning Framework for Laser Interstitial Thermal Therapy (LITT).

Develop a treatment planning framework for neurosurgeons treating high-grade gliomas with LITT to minimize the learning curve and improve tumor thermal dose coverage. Deidentified patient images were segmented using the image segmentation software Materialize MIMICS©. Segmented images were imported into the commercial finite element analysis (FEA) software COMSOL Multiphysics© to perform bioheat transfer simulations. The laser probe was modeled as a cylindrical object with radius 0.7 mm and length 100 mm, with a constant beam diameter. A modeled laser probe was placed in the tumor in accordance with patient specific patient magnetic resonance temperature imaging (MRTi) data. The laser energy was modeled as a deposited beam heat source in the FEA software. Penne's bioheat equation was used to model heat transfer in brain tissue. The cerebrospinal fluid (CSF) was modeled as a solid with convectively enhanced conductivity to capture heat sink effects. In this study, thermal damage-dependent blood perfusion was assessed. Pulsed laser heating was modeled based on patient treatment logs. The stationary heat source and pullback heat source techniques were modeled to compare the calculated tissue damage. The developed bioheat transfer model was compared to MRTi data obtained from a laser log during LITT procedures. The application builder module in COMSOL Multiphysics© was utilized to create a Graphical User Interface (GUI) for the treatment planning framework. Simulations predicted increased thermal damage (10-15%) in the tumor for the pullback heat source approach compared with the stationary heat source. The model-predicted temperature profiles followed trends similar to those of the MRTi data. Simulations predicted partial tissue ablation in tumors proximal to the CSF ventricle. A mobile platform-based GUI for bioheat transfer simulation was developed to aid neurosurgeons in conveniently varying the simulation parameters according to a patient-specific treatment plan. The convective effects of the CSF should be modeled with heat sink effects for accurate LITT treatment planning.

Technical Note: Advantages of a 2-Room Intraoperative 3-Tesla Magnetic Resonance Imaging Operating Suite for Performing Laser Interstitial Thermal Therapy in Pediatric Epilepsy and Tumor Surgery

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. 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. 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. 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.

LMAP-18 ADAPTING LASER INTERSTITIAL THERMAL THERAPY (LITT) FOR TREATMENT OF INTRACRANIAL LESIONS IN CANINES

Abstract Malignant gliomas are devastating intracranial tumors with dismal prognoses that impose unique therapeutic challenges. Treatment options include surgical resection, radiation, and chemotherapy, but efficacy is limited and carries associated morbidity. Promise persists for newer modalities, such as immune-based platforms, but the blood-brain barrier (BBB) restricts intracranial therapeutic access, limiting success. Laser interstitial thermal therapy (LITT) is a minimally invasive surgical intervention permitting thermal ablation of brain tumors and other intracranial lesions. During LITT, a laser probe is stereotactically introduced through a small skull burr hole into the lesion. Continuous MRI is used to conduct real-time temperature monitoring via software-based calculation of cumulative thermal dosage zones. LITT is not only capable of ablating neoplastic tissue, but can also open the BBB in peritumoral regions, and thus may synergize with other emerging therapies. We adapted a commercially available LITT system (Monteris Medical) for use in dogs with intracranial lesions. Canine cadavers were used to optimize LITT procedures before employing this platform in live dogs. Our approach consists of 1. obtaining volumetric, T1-weighted, MRI studies to plan trajectories to intracranial targets, 2. fixing canine patients to a surgical bed and registering them for surface matching to a volume rendered image, 3. using an integrated instrument holder (Varioguide, Brainlab) to guide drilling of 4.5 mm skull burr holes for placement of self-tapping titanium “mini-bolts” (Monteris Medical), and 4. introducing the laser catheter probe through the mini-bolts for lesion ablation in the MRI suite. This method allows for rigid stereotaxy, successful neuronavigation, and a minimally invasive approach. We have successfully performed LITT on four canine patients with spontaneously occurring intracranial gliomas and plan to treat additional canine patients with intracranial lesions. Future studies will explore combination therapeutic platforms, including immunotherapy and gold nanoparticles to improve the efficiency and specificity of tumor ablation.

Persistent Peri-Ablation Blood-Brain Barrier Opening After Laser Interstitial Thermal Therapy for Brain Tumors.

Purpose Laser interstitial thermal therapy (LITT) is a minimally invasive, image-guided, cytoreductive procedure to treat recurrent glioblastoma. This study implemented dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) methods and employed a model selection paradigm to localize and quantify post-LITT blood-brain barrier (BBB) permeability in the ablation vicinity. Serum levels of neuron-specific enolase (NSE), a peripheral marker of increased BBB permeability, were measured. Methods Seventeen patients were enrolled in the study. Using an enzyme-linked immunosorbent assay, serum NSE was measured preoperatively, 24 hours postoperatively, and at two, eight, 12, and 16 weeks postoperatively, depending on postoperative adjuvant treatment. Of the 17 patients, four had longitudinal DCE-MRI data available, from which blood-to-brain forward volumetric transfer constant (Ktrans) data were assessed. Imaging was performed preoperatively, 24 hours postoperatively, and between two and eight weeks postoperatively. Results Serum NSE increased at 24 hours following ablation (p=0.04), peaked at two weeks, and returned to baseline by eight weeks postoperatively. Ktrans was found to be elevated in the peri-ablation periphery 24 hours after the procedure. This increase persisted for two weeks. Conclusion Following the LITT procedure, serum NSE levels and peri-ablation Ktrans estimated from DCE-MRI demonstrated increases during the first two weeks after ablation, suggesting transiently increased BBB permeability.

Laser interstitial thermal therapy in the treatment of brain metastases: the relationship between changes in postoperative magnetic resonance imaging characteristics and tumor recurrence.

Laser interstitial thermal therapy (LITT) has been used to treat brain metastases (BMs) in several countries, and its safety and effectiveness have been confirmed. In most cases, magnetic resonance imaging (MRI) reveals an increase in tumor volume with an enhanced margin after LITT. However, little is known about the relationship between this MRI change and tumor recurrence. We report the first case series of BMs treated by LITT in China to evaluate the clinical characteristics and predictive factors of tumor recurrence. Patients with less than four brain metastatic lesions and a Karnofsky performance status (KPS) > 70 were eligible for study inclusion. Standard LITT procedures were performed, and a follow-up MRI was performed to analyze the radiographic changes, especially the volume ratio of the enhanced margin and the whole lesion on MRI at 30days postoperatively. All the volume-related data were delineated and calculated using 3D Slicer software. Related predictors were also collected to evaluate the correlation with local tumor control. Eighteen patients with nineteen lesions were enrolled for treatment and follow-up. Primary tumor histology included pulmonary carcinoma (n = 11) and breast cancer (n = 4). On average, the tumor size measured 3.01 cm3 (range, 0.40-7.40 cm3), the total ablation time was 13.58min (range, 2.88-37.15min), and the complete ablation rate was 92.4% (range, 29.2-100%). Comparing 3s0-day follow-up MRI results with preoperative MRI findings, 18 lesions showed a 2.28-fold (range, 1.21-4.88) volume increase; all the lesions displayed an enhanced component with a volume ratio of 42.35% (range, 10.14-100%). Five patients experienced tumor recurrence, and the local tumor control rates at 90days and 180days of follow-up were 68.4% and 66.7%, respectively. Univariate analysis indicated that the primary tumor, ablation rate, and enhanced volume ratio (EVR) > 40% in the 30-day MRI were associated with tumor recurrence, whereas multivariate analysis showed that only EVR > 40% was a predictive factor of local control. LITT is a minimally invasive method used to ablate brain metastases which can be used as the first-line treatment for BM patients under certain indications. After LITT, most tumors showed volume enlargement on the 30-day MRI scan, and EVR > 40% on the 30-day MRI may indicate late tumor recurrence.

Magnetic resonance imaging-guided laser interstitial thermal therapy for complete corpus callosotomy: technique and 1-year outcomes. Patient series.

Magnetic resonance imaging (MRI)-guided stereotactic laser interstitial thermal therapy (LITT) is a minimally invasive technique that has been described for the treatment of certain forms of epilepsy through partial or complete callosotomy, with few cases describing single-stage complete LITT callosotomy. The authors aimed to demonstrate this technique's feasibility and efficacy through description of the technique and 1-year outcomes in 3 cases of single-stage complete LITT callosotomy in patients with anatomically normal corpa callosa (CCs). The patients were aged 14-27 years and experienced atonic seizures. Completeness of callosotomy was determined from MRI scans obtained >3 months after LITT procedures. The estimated ablations of the CC were 94%, 89%, and 100%, respectively. The second patient had a catheter breach the lateral ventricle, resulting in the lowest estimated percentage of ablation in this series (89%), with minimal atonic seizure reduction. The first patient had significant reduction in atonic seizure frequency, and the third patient had complete resolution of atonic seizures. None of the patients experienced any long-term complications. Intensive care length of stay was 1 night for each patient, and total length of stay was between 2 and 7 nights. Postoperative follow-up was between 14 and 18 months. Complete laser callosotomy is achievable and is a safe alternative to microsurgical or endoscopic approaches.

SURG-22. STAGED LASER INTERSTITIAL THERAPY (LITT) FOR THE SURGICAL TREATMENT OF INSULAR GLIOMA: A CASE SERIES WITH A NOVEL TREATMENT PARADIGM

Abstract BACKGROUND Insular gliomas pose a significant surgical challenge due to the insula’s delicate surrounding functional and vascular anatomy. Insular gliomas are conventionally treated with open surgical resection augmented by several surgical adjuvants. Despite advancements in technology and surgical techniques, surgical resection of insular gliomas has been associated with frequent and potentially severe morbidity. Laser interstitial thermal therapy (LITT) is a novel, cytoreductive, and less-invasive treatment option for glioma. OBJECTIVE We describe the first-ever series of patients with insular glioma treated with staged LITT with or without subsequent craniotomy. METHODS A retrospective institutional database identified patients with insular glioma who underwent staged LITT treatments. Clinical, histopathological, and volumetric lesional characteristics were obtained. Procedural characteristics, morbidity, overall survival (OS), and progression-free survival (PFS) were determined. RESULTS Between 2019-2022, 11 patients with insular glioma were treated in stages with a total of 21 LITT procedures with or without subsequent craniotomy. Four patients had Diffuse Astrocytoma (IDHmt/TP53+), one Gemistocytic Astrocytoma (IDHmt/TP53+), three Anaplastic Astrocytoma (IDHmt/TP53+), one Anaplastic Oligodendroglioma (IDHmt/1p19q codel), one secondary GBM (IDHmt/TP53+), and one GBM (IDHwt/TP53-). Six patients were treated with LITT alone, while five patients were treated with LITT followed by a craniotomy for complete resection. Patients had a median tumor volume of 31.5 cm3 (9.58, 97) and a mean extent of ablation±resection of 97.68% (S.D. 5.4). At a median follow-up of 12.59 months, patients had a median PFS of 12.88 months and an OS of 14.46 months. No patients had a change in KPS following LITT. Two patients had a decrease in KPS following surgery. CONCLUSION We present the first-ever reported series of insular glioma treated with staged LITT with/without subsequent resection. We found that staged treatment of insular gliomas with LITT is safe, effective, and a minimally invasive option that avoids the potentially significant morbidity associated with conventional surgery.

DISP-15. TRENDS IN LASER INTERSTITIAL THERMAL THERAPY (LITT): HOW RACE AND SOCIOECONOMIC FACTORS IMPACT ACCESS

Abstract Introduction This study seeks to examine the trends of laser interstitial thermal therapy (LITT) access in the pre-and post-Medicaid expansion time periods; and more specifically, how racial and socioeconomic factors impact access. Methods The National Inpatient Sample (NIS) database was queried for all patients who received LITT from 2010 to 2019 for any indication. Age, gender, race, payer status, and median income by zip code were obtained and compared for the pre-Medicaid expansion (2010-2014), and post-Medicaid expansion (2015-2019) groups. Chi-square analysis was performed for categorical variables, and the student t-test was used to analyze continuous variables. Results The pre-Medicaid expansion (n = 915) and post-Medicaid (n = 3205) time periods were similar in that Whites were the overwhelming majority of LITT recipients (78.7% and 70.8%, p &amp;lt; 0.001). In 2010, all races had low rates of LITT, as would be expected with a new emerging treatment. Although the absolute value of the percentages seems similar, between 2013 and 2014, the proportion of Whites receiving LITT nearly doubled (from 45% to 75%); while all other groups had no significant increase in utilization. Utilization of LITT by Black Americans remained stable, 5.4% and 5.6% in the pre- and post-Medicaid expansion eras, while Hispanics and Others saw slight increases in utilization (8.8% to 10.1% and 7.1% to 13.4% respectively). Although Medicare and Medicaid usage increased over the years, private insurance remained the primary payer for LITT (53.8% and 49.3%, p 0.018). Lastly, patients within the highest income quartiles comprised over half of LITT procedures done in the study period (56.8% and 52.8%, p 0.029). Conclusion Despite nearly a decade and the effects of Medicaid expansion via the Affordable Care Act, LITT is still difficult to access for patients of color, Medicare and Medicaid users, and patients in low-income locales.

Technical challenges to anterior temporal lobectomy after laser interstitial thermal therapy for mesial temporal lobe epilepsy: technical note.

Mesial temporal sclerosis (MTS) is a frequent cause of medically refractory epilepsy, for which laser interstitial thermal therapy (LITT) is an effective treatment. However, experience with the technical considerations posed by additional surgery after an initial LITT procedure is lacking. The authors present the case of a 12-year-old female with medically refractory temporal lobe epilepsy and left MTS who underwent LITT at a separate institution prior to referral. This patient had no change in early postoperative seizure control (Engel class IVB) and then her seizures worsened despite ongoing medical treatment (Engel class IVC). Post-LITT MRI revealed sparing of the mesial hippocampus head, a poor prognostic factor. The authors describe the technical details illustrated by this case of secondary, stereotactic electroencephalography-guided mesial temporal resection following LITT. The case was managed with anterior temporal lobectomy including the resection of residual hippocampus and amygdala.

Laser Interstitial Thermal Therapy for Cavernous Malformations: A Systematic Review.

BackgroundMicrosurgical resection of intracranial cavernous malformations (CM) is regarded as the standard treatment, but in recent years, there has been a trend toward minimally invasive procedures like ablation of such lesions by using laser interstitial thermal therapy (LITT).MethodsA systematic search using keywords ‘laser interstitial thermal therapy’ OR ‘LITT’ AND ‘cavernoma’ OR ‘cavernous angiomas’ OR ‘cavernous malformations’ was conducted in MEDLINE (PubMed), Scopus, Embase, and Cochrane electronic bibliographic databases and studies reporting the outcome of LITT procedure on intracranial CM were included. The demographic data, symptoms of patients, location and size of the lesion, and surgical outcome were extracted from the articles.ResultSix studies, reporting the outcome of 33 patients were included in this review. In 26 patients, CM was identified as the epileptogenic foci and in others, CM was the source of headache or focal neurological deficits. LITT led to a satisfactory outcome in all patients except for three who achieved improvement in symptoms after the open resection of the lesion. Most of the post-operative complications were transient and resolved at the time of the last follow up. Cyst formation at the previous ablated CM site was reported as the long-term complication of LITT in one case.ConclusionLITT can provide a comparable outcome to the open resection of CMs, by having less invasiveness, even in deep and eloquent area lesions, and complications that are often temporary and disappear gradually. However, technical issues, such as thermal monitoring during the procedure, are considered a challenge for this procedure in CMs. Further studies with a larger population are needed to report this method's long-term outcome and complications on CMs.

Adaptation of laser interstitial thermal therapy for tumor ablation under MRI monitoring in a rat orthotopic model of glioblastoma.

Laser interstitial thermal therapy (LITT) under magnetic resonance imaging (MRI) monitoring is being increasingly used in cytoreductive surgery of recurrent brain tumors and tumors located in eloquent brain areas. The objective of this study was to adapt this technique to an animal glioma model. A rat model of U251 glioblastoma (GBM) was employed. Tumor location and extent were determined by MRI and dynamic contrast-enhanced (DCE) MRI. A day after assessing tumor appearance, tumors were ablated during diffusion-weighted imaging (DWI)-MRI using a Visualase LITT system (n = 5). Brain images were obtained immediately after ablation and again at 24h post-ablation to confirm the efficacy of tumor cytoablation. Untreated tumors served as controls (n = 3). Rats were injected with fluorescent isothiocyanate (FITC) dextran and Evans blue that circulated for 10min after post-LITT MRI. The brains were then removed for fluorescence microscopy and histopathology evaluations using hematoxylin and eosin (H&E) and major histocompatibility complex (MHC) staining. All rats showed a space-occupying tumor with T2 and T1 contrast-enhancement at pre-LITT imaging. The rats that underwent the LITT procedure showed a well-demarcated ablation zone with near-complete ablation of tumor tissue and with peri-ablation contrast enhancement at 24h post-ablation. Tumor cytoreduction by ablation as seen on MRI was confirmed by H&E and MHC staining. Data showed that tumor cytoablation using MRI-monitored LITT was possible in preclinical glioma models. Real-time MRI monitoring facilitated visualizing and controlling the area of ablation as it is otherwise performed in clinical applications.

Intracranial EEG and laser interstitial thermal therapy in MRI-negative insular and/or cingulate epilepsy: case series.

The goal of this study was to assess the success rate and complications of stereo-electroencephalogra-phy (sEEG) and laser interstitial thermal therapy (LITT) in the treatment of nonlesional refractory epilepsy in cingulate and insular cortex. The authors retrospectively analyzed the treatment response in 9 successive patients who underwent insular or cingulate LITT for nonlesional refractory epilepsy at their center between 2011 and 2019. Localization of seizures was based on inpatient video-EEG monitoring, neuropsychological testing, 3-T MRI, PET scan, magnetoencephalography scan, and/or ictal SPECT scan. Eight patients underwent sEEG, and 1 patient had implantation of both sEEG electrodes and subdural grids for localization of epileptogenic zones. LITT was performed in 5 insular cases (4 left and 1 right) and 3 cingulate cases (all left-sided). One patient also underwent both insular and cingulate LITT on the left side. All of the patients who underwent insular LITT as well as 2 of the 3 who underwent cingulate LITT were right-hand dominant. The patient who underwent insular plus cingulate LITT was also right-hand dominant. Following LITT, 67% of the patients were seizure free (Engel class I) at follow-up (mean 1.35 years, range 0.6-2.8 years). All patients responded favorably to treatment (Engel class I-III). Two patients developed small intracranial hemorrhages during the sEEG implantation that did not require surgical management. One patient developed a large intracranial hemorrhage during an insular LITT procedure that did require surgical management. That patient experienced aphasia, incoordination, and hemiparesis, which resolved with inpatient rehabilitation. No permanent neurological deficits were noted in any of the patients at last follow-up. Neuropsychological status was stable in this cohort before and after LITT. sEEG can be safely used to localize seizures originating from insular and cingulate cortex. LITT can successfully treat seizures arising from these deep-seated structures. The insula and cingulum should be evaluated more frequently for seizure onset zones.