Resonance-guided Laser Interstitial Thermal Therapy Research Articles

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.

Negative MRI and a seizure onset zone close to eloquent areas in FCD type II: Application of MRg-LiTT after a SEEG re-evaluation in pediatric patients with a previous failed surgery

ObjectiveNegative MRI and an epileptogenic zone (EZ) adjacent to eloquent areas are two main issues that can be encountered during pre-surgical evaluation for epilepsy surgery. Focal Cortical Dysplasia type II (FCD type II) is the most common aetiology underlying a negative MRI.The objective of this study is to present three cases of pediatric patients exhibiting negative MRI and a seizure onset zone close to eloquent areas, who previously underwent traditional open surgery or SEEG-guided radiofrequency thermocoagulations (RF-TC). After seizure seizure recrudescence, pre-surgical SEEG was re-evaluated and Magnetic Resonance-guided laser interstitial thermal therapy (MRg-LiTT) was performed.We discuss the SEEG patterns, the planning of laser probes trajectories and the outcomes one year after the procedure. MethodsPediatric patients who underwent SEEG followed by MRg-LiTT for drug-resistant epilepsy associated with FCD type II at our Centre were included. Pre-surgical videoEEG (vEEG), stereoEEG (sEEG), and MRI were reviewed. Post-procedure clinical outcome (measured by Engel score) and complications rates were evaluated. ResultsThree patients underwent 3 MRg-LiTT procedures from January 2022 to June 2022. Epileptogenic zone was previously studied via SEEG in all the patients. All the three patients pre-surgical MRI was deemed negative. Mean age at seizure onset was 47 months (21–96 months), mean age at MRg-LiTT was 12 years (10 years 10 months – 12 years 9 months). Engel class Ia outcome was achieved in patients #2 and #3, Engel class Ib in patient #1. Mean follow-up length was of 17 months (13 months – 20 months). Complications occurred in one patient (patient #2, extradural hematoma). ConclusionsThe combined use of SEEG and MRg-LiTT in complex cases can lead to good outcomes both as a rescue therapy after failed surgery, but also as an alternative to open surgery after a successful SEEG-guided Radiofrequency Thermocoagulation (RF-TC). Specific SEEG patterns and a previous good outcome from RF-TC can be predictors of a favourable outcome.

Magnetic Resonance–Guided Laser Interstitial Thermal Therapy for Recurrent Glioblastoma and Radiation Necrosis: A Single-Surgeon Case Series

Evaluate long-term clinical outcomes among patients treated with laser interstitial thermal therapy (LITT) for predicted recurrent glioblastoma (rGBM). Patients with rGBM treated by LITT by a single surgeon (2013-2020) were evaluated for progression-free survival (PFS), overall survival (OS), and OS after LITT. Forty-nine patients (33 men, 16 women; mean [SD] age at diagnosis, 58.7 [12.5] years) were evaluated. Among patients with genetic data, 6 of 34 (18%) had IDH-1 R132 mutations, and 7 of 21 (33%) had MGMT methylation. Patients underwent LITT at a mean (SD) 23.8 (23.8) months after original diagnosis. Twenty of 49 (40%) had previous stereotactic radiosurgery, 37 (75%) intensity-modulated radiation therapy, and 49 (100%) chemotherapy. Patients had a mean 1.2 (0.7) previous resections before LITT. Mean preoperative enhancing and T2 FLAIR volumes were 13.1 (12.8) cm3 and 35.0 (32.8) cm3, respectively. Intraoperative biopsies confirmed rGBM in 31 (63%) and radiation necrosis in 18 (37%). Six perioperative complications occurred: 3 (6%) cases of worsening aphasia, 1 (2%) seizure, 1 (2%) epidural hematoma, and 1 (2%) intraparenchymal hemorrhage. For the rGBM group, median PFS was 2.0 (IQR, 4.0) months, median OS was 20.0 (IQR, 29.5) months, and median OS after LITT was 6.0 (IQR, 10.5) months. For the radiation necrosis group, median PFS was 4.0 (IQR, 4.5) months, median OS was 37.0 (IQR, 58.0) months, and median OS after LITT was 8.0 (IQR, 23.5) months. In a diverse rGBM cohort, LITT was associated with a short duration of posttreatment PFS.

A - 11 Cognitive and Clinical Correlates of Olfactory Function in Adults with Epilepsy.

Olfactory dysfunction is well-documented in epilepsy. We recently found that olfactory assessment may have clinical utility in identifying surgical candidates with intractable epilepsy who benefit from magnetic resonance-guided laser interstitial thermal therapy (MRgLiTT). However, the demographic, clinical, and cognitive correlates of olfaction in epilepsy remain unclear and could aid in understanding its potential utility in clinical examinations. We identified 60 outpatients with epilepsy (mean age = 38.22 ± 13.84years; 50% male; 89.3% right-handed; seizure location: 45.0% left, 33.3% right, 13.3% bilateral, 8.3% unspecified) referred for neuropsychological evaluation in the Johns Hopkins Division of Medical Psychology Clinic. Neuropsychological evaluation included the 16-item Sniffin' Sticks Odor Identification Test. Linear regression models were used to examine associations between 1) olfaction and demographic/clinical characteristics (age, sex, education, duration of illness, seizure laterality) and 2) olfaction and cognition (processing speed, language, auditory-verbal and visuospatial memory, executive functioning; adjusted for demographic/clinical characteristics). Olfactory performance was not significantly associated with demographic or clinical characteristics. Across all participants, better olfactory performance was associated with better auditory-verbal memory (B = 5.04, t(46) = 4.16, p < 0.001) and visual confrontation naming (B = 1.53, t(45) = 4.11, p < 0.001) with correction for multiple comparisons. In a subset with lateralizing epilepsy (n = 47), better odor identification performance remained a significant predictor of the aforementioned cognitive measures with adjustment for demographic and clinical characteristics. Consistent with work in other neurologic conditions, our preliminary findings indicate that olfactory function is associated with verbally-mediated neuropsychological measures in epilepsy. Future studies utilizing pre-surgical neuroimaging will examine the association between olfaction, cognition, and radiographic markers of tissue integrity in epilepsy.

Long-term outcomes of mesial temporal laser interstitial thermal therapy for drug-resistant epilepsy and subsequent surgery for seizure recurrence: a multi-centre cohort study

BackgroundMagnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive alternative to surgical resection for drug-resistant mesial temporal lobe epilepsy (mTLE). Reported rates of seizure freedom are variable and...

Correlating Thermodynamics with Cognitive Outcomes in Magnetic Resonance-guided Laser Interstitial Thermal Therapy (MRgLITT) of a Pediatric Hypothalamic Hamartoma

Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a commonly used clinical method of destroying intracranial brain foci. Our objective was to correlate the thermal damage estimate transition zone with cognitive outcomes in MRgLITT of a pediatric hypothalamic hamartoma. Uncomplicated MRgLITT was used to disconnect an 8-mm left Delalande grade II hypothalamic hamartoma (HH) revealed on neuroimaging of a 17-year-old male patient with drug-resistant epilepsy and a "gelastic+" semiology including both gelastic and tonic-clonic seizures. Despite meticulous planning, submillimetric stereotactic accuracy, and reassuring intraoperative thermography, the patient experienced transient, but profound, global amnesia. Retroactively, we applied a new iteration of thermographic software that overlays a magenta-colored transition zone (TZ) around the necrotic zone defined by the orange-pigmented thermal damage estimate (TDE). Clear involvement of the bilateral mesial circuits was demonstrated by the overlay of the TZ on the TDE. Involvement of the bilateral mesial circuits visualized with TDE and TZ could account for the neurocognitive outcomes of our patient. We highlight this case as our understanding of thermography analysis evolves, emphasizing principles of technique and trajectory planning, as well as considerations during thermablation to help inform surgical decision-making.

Craniofacial Encephalocele: Updates on Management.

Craniofacial encephaloceles are rare, yet highly debilitating neuroanatomical abnormalities that result from herniation of neural tissue through a bony defect and can lead to death, cognitive delay, seizures, and issues integrating socially. The etiology of encephaloceles is still being investigated, with evidence pointing towards the Sonic Hedgehog pathway, Wnt signaling, glioma-associated oncogene (GLI) transcription factors, and G protein-coupled receptors within primary cilia as some of the major genetic regulators that can contribute to improper mesenchymal migration and neural tube closure. Consensus on the proper approach to treating craniofacial encephaloceles is confounded by the abundance of surgical techniques and parameters to consider when determining the optimal timing and course of intervention. Minimally invasive approaches to encephalocele and temporal seizure treatment have increasingly shown evidence of successful intervention. Recent evidence suggests that a single, two-stage operation utilizing neurosurgeons to remove the encephalocele and plastic surgeons to reconstruct the surrounding tissue can be successful in many patients. The HULA procedure (H = hard-tissue sealant, U = undermine and excise encephalocele, L = lower supraorbital bar, A = augment nasal dorsum) and endoscopic endonasal surgery using vascularized nasoseptal flaps have surfaced as less invasive and equally successful approaches to surgical correction, compared to traditional craniotomies. Temporal encephaloceles can be a causative factor in drug-resistant temporal seizures and there has been success in curing patients of these seizures by temporal lobectomy and amygdalohippocampectomy, but magnetic resonance-guided laser interstitial thermal therapy has been introduced as a minimally invasive method that has shown success as well. Some of the major concerns postoperatively include infection, cerebrospinal fluid (CSF) leakage, infringement of craniofacial development, elevated intracranial pressure, wound dehiscence, and developmental delay. Depending on the severity of encephalocele prior to surgery, the surgical approach taken, any postoperative complications, and the age of the patient, rehabilitation approaches may vary.

Appearance and modeling of bubble artifacts in intracranial magnetic resonance-guided laser interstitial thermal therapy (MRg-LITT) temperature images

PurposeTo understand if unexplained signal artifacts in MRg-LITT proton resonance frequency- (PRF-) shift thermometry images are caused by air bubbles or hemorrhages, and to characterize their effects on temperature measurements. MethodsRetrospective image data from an IRB-approved clinical trial of intracranial MRg-LITT were inspected for asymmetric distortions observed in phase data during ablations, which have been previously reported as likely hemorrhages. A total of eight patient cases were selected: seven with artifact occurrence and one without. Mathematical image models for air bubbles or hemorrhages were implemented to estimate the size of the air bubble or hemorrhage needed to explain the clinically observed phase artifacts. Correlations and Bland-Altman analyses were used to determine if an air bubble model or a hemorrhage model was better correlated to the clinical data. The model was used to inject bubbles into clean PRF phase data without artifacts to examine how temperature profile distortions change with slice orientation. The simulated air-bubble injected data were compared to clinical data containing artifacts to examine the bubbles' effects on temperature and thermal damage estimates. ResultsThe model demonstrated that air bubbles up to approximately 1 cm in diameter could explain the clinically observed phase artifacts. The bubble model predicts that a hemorrhage would have to be 2.2 times as large as an air bubble in order to explain the same extent of phase distortion observed in clinical data. Air bubbles had 16% percent higher correlations to the clinical PRF phase data than hemorrhages, even after rescaling the hemorrhage phases to better match the data. The air bubble model also explains how the phase artifacts lead to both large positive and large negative temperature errors, up to ±100 °C, which could cascade to damage estimate errors of several millimeters. ConclusionResults showed that the artifacts are likely caused by air bubbles rather than hemorrhages, which may be introduced before heating or appear during heating. Manufacturers and users of devices that rely upon PRF-shift thermometry should be aware these phase distortions from bubble artifacts can result in large temperature errors.

Single-Institution Comparative Study of Magnetic Resonance–Guided Laser Interstitial Thermal Therapy and Open Corpus Callosotomy

Open corpus callosotomy (CC) poses a higher risk of perioperative morbidity than does magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) for treatment of drop and generalized seizures without documented superiority. We present a single-institution comparison between open and MRgLITT CC. A 2-year retrospective review was performed of patients who underwent open and MRgLITT CC (January 2019-January 2021). Demographics, surgical outcome data, hospital costs, and interhemispheric connectivity with diffusion tensor imaging were compared. The average age in years was 9.3 and 11.4 for CC (n= 4) and MRgLITT (n= 9), respectively. Preoperative drop seizure frequency was higher in CC (25 vs. 14.5 seizures/day; P= 0.59). At 10 months follow-up, the reduction in drop seizure frequency was better in open CC, but not statistically significant (93.8% vs. 64.3%; P= 0.21). The extent of CC ablation did not correlate with seizure reduction (Pearson coefficient= 0.09). An inverse correlation between interhemispheric connectivity change (diffusion tensor imaging analysis) and drop seizure frequency reduction was noted (Pearson coefficient= -0.97). Total hospital cost was significantly lower in MRgLITT ($67,754 vs. $107,111; P= 0.004), attributed to lower intensive care unit (1.1 vs. 4 days; P= 0.004) and total hospital stay (1.8 vs. 10.5 days; P= 0.0001). Postoperative hydrocephalus was present in 75% of patients in the CC group compared with zero in the MRgLITT group. Our middle-volume single-institution experience shows the safety, efficacy, and cost-effective benefit of MRgLITT compared with the traditional CC with therapeutic equipoise. This study is limited by the number of patients and, hence, further patient enrollment or multicenter study is warranted.

Insula in epilepsy – “untying the gordian knot”: A systematic review

PurposeDespite significant advances in epileptology, there are still many uncertainties about the role of the insula in epilepsy. Until recently, most insular onset seizures were wrongly attributed to the temporal lobe. Further, there are no standardised approaches to the diagnosis and treatment of insular onset seizures. This systematic review gathers the available information about insular epilepsy and synthesizes current knowledge as a basis for future research. MethodAdhering to the PRISMA guidelines, studies were meticulously extracted from the PubMed database. The empirical data pertaining to the semiology of insular seizures, insular networks in epilepsy, techniques of mapping the insula, and the surgical intricacies of non-lesional insular epilepsy were reviewed from published studies. The corpus of information available was then subjected to a process of concise summarization and astute synthesis. ResultsOut of 235 studies identified for full-text review, 86 studies were included in the systematic review. The insula emerges as a brain region with a number of functional subdivisions. The semiology of insular seizures is diverse and depends on the involvement of particular subdivisions. The semiological heterogeneity of insular seizures is explained by the extensive connectivity of the insula and its subdivisions with all four lobes of the brain, deep grey matter structures, and remote brainstem areas. The mainstay of the diagnosis of seizure onset in the insula is stereoelectroencephalography (SEEG). The surgical resection of the insular epileptogenic zone (when possible) is the most effective treatment. Open surgery on the insula is challenging but magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) also holds promise. ConclusionThe physiological and functional roles of the insula in epilepsy have remained obfuscated. The dearth of precisely defined diagnostic and therapeutic protocols acts as an impediment to scientific advancement. This review could potentially facilitate forthcoming research endeavours by establishing a foundational framework for uniform data collection protocols, thereby enhancing the feasibility of comparing findings across future studies and promoting progress in this domain.

Intraoperative electrocorticography during laser-interstitial thermal therapy predicts seizure outcome in mesial temporal lobe epilepsy

ObjectiveMagnetic resonance-guided laser interstitial thermal therapy (MRLiTT) for treating temporal lobe epilepsy has recently gained popularity. We aimed to investigate the predictive value of pre-and post-MRLiTT epileptiform discharges (EDs) on intraoperative electrocorticography (iECoG) in seizure outcomes for patients with mesial temporal lobe epilepsy (mTLE). MethodsWe conducted a pilot, prospective single-center cohort study on seven consecutive patients with mTLE that underwent MRLiTT. Pre- and post-MRLiTT iECoG was performed using a 1x8 contact depth electrode along the same trajectory used for the laser catheter. ResultsThe responders had a robust reduction in ED frequency compared to pre-MRLiTT iECoG (86% vs 13%, p < 0.01). Clinical characteristics, including risk factors for epilepsy, duration of epilepsy, presence of mesial temporal lobe sclerosis, prior intracranial monitoring, the absolute frequency of pre- or post-MRLiTT EDs, and ablation volume were not significantly associated with responder status. ConclusionsThis is the first demonstration that intraoperative reduction in EDs during mesial temporal lobe MRLiTT may potentially predict seizure outcomes and may serve as an intraoperative biomarker for satisfactory ablation. However, larger prospective studies are needed to confirm our findings and evaluate the utility of iECoG during MRLiTT. SignificanceiECoG during mesial temporal lobe MRLiTT may help assess seizure outcomes.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Management of Low-Grade Gliomas and Radiation Necrosis: A Single-Institution Case Series.

Laser interstitial thermal therapy (LITT) has emerged as a minimally invasive treatment modality for ablation of low-grade glioma (LGG) and radiation necrosis (RN). To evaluate the efficacy, safety, and survival outcomes of patients with radiographically presumed recurrent or newly diagnosed LGG and RN treated with LITT. The neuro-oncological database of a quaternary center was reviewed for all patients who underwent LITT for management of LGG between 1 January 2013 and 31 December 2020. Clinical data including demographics, lesion characteristics, and clinical and radiographic outcomes were collected. Kaplan-Meier analyses comprised overall survival (OS) and progression-free survival (PFS). Nine patients (7 men, 2 women; mean [SD] age 50 [16] years) were included. Patients underwent LITT at a mean (SD) of 11.6 (8.5) years after diagnosis. Two (22%) patients had new lesions on radiographic imaging without prior treatment. In the other 7 patients, all (78%) had surgical resection, 6 (67%) had intensity-modulated radiation therapy and chemotherapy, respectively, and 4 (44%) had stereotactic radiosurgery. Two (22%) patients had lesions that were wild-type IDH1 status. Volumetric assessment of preoperative T1-weighted contrast-enhancing and T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences yielded mean (SD) lesion volumes of 4.1 (6.5) cm3 and 26.7 (27.9) cm3, respectively. Three (33%) patients had evidence of radiographic progression after LITT. The pooled median (IQR) PFS for the cohort was 52 (56) months, median (IQR) OS after diagnosis was 183 (72) months, and median (IQR) OS after LITT was 52 (60) months. At the time of the study, 2 (22%) patients were deceased. LITT is a safe and effective treatment option for management of LGG and RN, however, there may be increased risk of permanent complications with treatment of deep-seated subcortical lesions.

Epilepsy Surgery in Young Children With Tuberous Sclerosis Complex: A Novel Hybrid Multimodal Surgical Approach.

Surgery has become integral in treating children with tuberous sclerosis complex (TSC)-related drug-resistant epilepsy (DRE). To describe outcomes of a multimodal diagnostic and therapeutic approach comprising invasive intracranial monitoring and surgical treatment and compare the complementary techniques of open resection and magnetic resonance-guided laser interstitial thermal therapy. Clinical and radiographic data were prospectively collected for pediatric patients undergoing surgical evaluation for TSC-related DRE at our tertiary academic hospital. Seizure freedom, developmental improvement, and Engel class were compared. Thirty-eight patients (20 females) underwent treatment in January 2016 to April 2019. Thirty-five underwent phase II invasive monitoring with intracranial electrodes: 24 stereoencephalography, 9 craniotomy for grid/electrode placement, and 2 grids + stereoencephalography. With the multimodal approach, 33/38 patients (87%) achieved >50% seizure freedom of the targeted seizure type after initial treatment; 6/9 requiring secondary treatment and 2/2 requiring a third treatment achieved >50% freedom. The median Engel class was II at last follow-up (1.65 years), and 55% of patients were Engel class I/II. The mean age was lower for children undergoing open resection (2.4 vs 4.9 years, P = .04). Rates of >50% reduction in seizures (86% open resection vs 88% laser interstitial thermal therapy) and developmental improvement (86% open resection vs 83% magnetic resonance-guided laser interstitial thermal therapy) were similar. This hybrid approach of using both open surgical and minimally invasive techniques is safe and effective in treating DRE secondary to TSC. Clinical trials focused on treatment method with longer follow-up are needed to determine the optimal candidates for each approach and compare the treatment modalities more effectively.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Hypothalamic Hamartoma: Surgical Approach and Treatment Outcomes.

Hypothalamic hamartoma (HH) is a rare lesion consisting of normal neurons and neuroglia arranged in an abnormal pattern which usually causes gelastic seizures (GS). Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has been developed as a minimally invasive approach to treat HH and gradually become a first-line treatment. In total, this study enrolled 47 consecutive HH patients that underwent one round of ablation. Patients were followed for at least one year. Patients' medical records and surgical information were carefully reviewed, and univariate analyses were performed. Of the treated patients, 72.3% remained GS-free in this study, with an overall Engel class I rate of 68.1%. Long-term postoperative complications occurred in six patients. Factors associated with GS prognosis included Delalande classification (p = 0.033), HH volume (p = 0.01), and the ablation rate of the HH body (p = 0.035). The disconnection rate was 0.73 ± 0.14 in the Engel class Ia group as compared to 0.62 ± 0.13 in the Engel Ib-Engel IV group (p = 0.046). MRgLITT represents a safe and effective surgical procedure. Patients with larger or Delalande type IV HH may require multiple rounds of ablation. In addition to assessing the degree of disconnection, ablation volume should also be carefully considered for patients undergoing this procedure.

Automated Detection and Surgical Planning for Focal Cortical Dysplasia with Multicenter Validation.

In patients with surgically amenable focal cortical dysplasia (FCD), subtle neuroimaging representation and the risk of open surgery lead to gaps in surgical treatment and delays in surgery. To construct an integrated platform that can accurately detect FCD and automatically establish trajectory planning for magnetic resonance-guided laser interstitial thermal therapy. This multicenter study included retrospective patients to train the automated detection model, prospective patients for model evaluation, and an additional cohort for construction of the automated trajectory planning algorithm. For automated detection, we evaluated the performance and generalization of the conventional neural network in different multicenter cohorts. For automated trajectory planning, feasibility/noninferiority and safety score were calculated to evaluate the clinical value. Of the 260 patients screened for eligibility, 202 were finally included. Eighty-eight patients were selected for conventional neural network training, 88 for generalizability testing, and 26 for the establishment of an automated trajectory planning algorithm. The model trained using preprocessed and multimodal neuroimaging displayed the best performance in diagnosing FCD (figure of merit = 0.827 and accuracy range = 75.0%-91.7% across centers). None of the clinical variables had a significant effect on prediction performance. Moreover, the automated trajectory was feasible and noninferior to the manual trajectory ( χ2 = 3.540, P = .060) and significantly safer (overall: test statistic = 30.423, P < .001). The integrated platform validated based on multicenter, prospective cohorts exhibited advantages of easy implementation, high performance, and generalizability, thereby indicating its potential in the diagnosis and minimally invasive treatment of FCD.

Association of intraoperative end-tidal carbon dioxide level with ablation volume during magnetic resonance-guided laser interstitial thermal therapy for mesial temporal lobe epilepsy.

Maximal safe ablation of target structures during magnetic resonance-guided laser interstitial thermal therapy (MRgLiTT) is critical to achieving good seizure outcome in patients with mesial temporal lobe epilepsy (mTLE). The authors sought to determine whether intraoperative physiological variables are associated with ablation volume during MRgLiTT. Patients with mTLE who underwent MRgLiTT at our institution from 2014 to 2019 were retrospectively analyzed. Ablation volume was determined with volumetric analysis of intraoperative postablation MR images. Physiological parameters (systolic blood pressure [SBP], diastolic blood pressure [DBP], mean arterial pressure [MAP], end-tidal carbon dioxide [ETCO2]) measured 40 minutes prior to ablation were analyzed. Univariate and multivariate regression analyses were performed to determine independent predictors of ablation volume. Forty-four patients met the inclusion criteria. The median (interquartile range) ablation volume was 4.27 (2.92-5.89) cm3, and median ablation energy was 7216 (6402-8784) J. The median MAP, SBP, DBP, and ETCO2 values measured during the 40-minute period leading up to ablation were 72.8 (66.2-81.5) mm Hg, 104.4 (96.4-114.4) mm Hg, 62.4 (54.1-69.8) mm Hg, and 34.1 (32.0-36.2) mm Hg, respectively. In univariate analysis, only total laser energy (r = 0.464, p = 0.003) and 40-minute average ETCO2 (r = -0.388, p = 0.012) were significantly associated with ablation volume. In multivariate analysis, only ETCO2 ≤ 33 mm Hg (p = 0.001) was significantly associated with ablation volume. Total ablation energy and ETCO2, but not blood pressure, may significantly affect ablation volume in mTLE patients undergoing MRgLiTT. Mild hypocapnia was associated with increased extent of ablation. Intraoperative monitoring and modulation of ETCO2 may help improve extent of ablation, prediction of ablation volume, and potentially seizure outcome.

342 Long-Term Follow-up of 54 Cases of Recurrent Glioblastoma Treated with Magnetic Resonance-Guided Laser Interstitial Thermal Therapy

INTRODUCTION: Magnetic resonance guided laser-induced thermal therapy (MRgLITT) is a novel minimally invasive procedural treatment for progressive cerebral lesions and cerebral edema related to post-radiation treatment effect. METHODS: We conducted a single-center retrospective study of pre-operative imaging, clinical characteristics and survival outcomes of 54 patients with previously treated (WHO Grade IV) between January 2013 to December 2020. RESULTS: The average age of patients was 58.7 ± 12.0 years. Patients underwent MRgLITT a median time of 21.6 ± 23.7 months from original diagnosis. 20% (n = 11) of patients had previous history of stereotactic radiosurgery, 61% (n = 33) intensity-modulated radiation therapy, and 80% (n = 43) chemotherapy. There was an average of 1.2 ± 0.7 prior surgical resections before MRgLITT was performed. 41% (n = 22) of patients were on dexamethasone at the time of treatment. The median pre-operative enhancing lesion volume on T1 gadolinium-enhanced magnetic resonance imaging (MRI) was 9.7 cm3 (standard error [SE], 2.0 cm3) and 27.0 cm3 (SE, 5.6 cm3) on T2 fluid-attenuated inversion recovery MRI. The pathology of the biopsies taken during MRgLITT confirmed tumor recurrence in 61% (n = 33) of patients, and treatment effect or reactive changes in 37% (n = 20) of patients. 67% (n = 28) experienced radiographic evidence of progression of the previously treated lesion, while 21% (n =9) and 12% (n = 5) experienced progression of a new lesion or both, respectively. Progression-free survival after MRgLITT was 3.5 months (standard error [SE], 0.6; 95% CI, 2.4-4.6). At the time of the study, 78% (n = 42) of patients were deceased. Mean overall survival time was 29.9 months (SE, 4.3; 95% CI, 21.4-38.3). Mean survival time after MRgLITT was 8.3 months (SE, 1.2; 95% CI, 5.9-10.6. Of the 12 remaining living patients, 36% (n = 4) had a decline in their clinical status at the time of last follow up, while 64% (n = 7) and 9% (n = 1) were stable or improved, respectively. Patients were followed for a mean time interval of 9.25 ± 12.2 months from MRgLITT. CONCLUSION: MRgLITT may be a viable, minimally invasive option for patients with glioblastoma but is associated with relatively short post-treatment progression-free survival.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Brainstem Pathologies

Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive and effective treatment option that can potentially treat deep-seated pathologies in cases without safe open surgical corridors. In the present report, we have described our experience using MRgLITT for brainstem pathologies. A retrospective medical record review and analysis were conducted for all patients who had undergone MRgLITT for pathologies within or closely surrounding the brainstem between 2011 and 2020. The patients had undergone stereotactic laser placement in the operating suite and were transported to the magnetic resonance imaging suite for laser ablation with real-time monitoring. The demographics, operative parameters, and complications were recorded. A total of 12 patients had undergone MRgLITT for brainstem pathologies. The average age of the patients was 47.6 years (range, 4-75 years). The pathologies included both primary and metastatic intracranial tumors. The average preablation volume of the targets was 2.4±0.50 cm3. The average ablation time was 324.3 ± 60.7 seconds, and the average postablation volume was 2.92±0.53 cm3. One perioperative mortality was directly related to the procedure and 7 patients developed postoperative deficits. Two patients had experienced a recurrence after MRgLITT and opted to undergo additional alternative treatment. The brainstem represents formidable territory even for minimally invasive procedures. The overall morbidity and mortality has remained high, and the probability of achieving a meaningful outcome must be carefully assessed.

Magnetic resonance-guided laser interstitial thermal therapy (MR-gLiTT) in pediatric epilepsy surgery: experience at Giannina Gaslini Children’s Hospital (Genoa, Italy)

Magnetic resonance-guided laser interstitial thermal therapy (MR-gLiTT) in pediatric epilepsy surgery: experience at Giannina Gaslini Children’s Hospital (Genoa, Italy)

Controlling Signal Artifact With Software Threshold Imaging for Magnetic Resonance-Guided Laser Interstitial Thermal Therapy.

Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) uses intraoperative temperature mapping and thermal damage estimates to guide ablations of intracranial targets. In select cases, signal artifact presents at the target site and impairs intraprocedural decision-making by obscuring the visualization of both temperature imaging and the thermal damage estimate calculation. To date, the etiology and impact of signal artifact are unknown. However, user-selected MRgLITT software settings may play a role in generating artifact. To assess the effect of the thresholding feature in MRgLITT software on signal artifact generation during intracranial ablations. Ablations were performed with the Visualase MRI-guided Laser Ablation System (Medtronic). For each LITT procedure, raw thermal data were extracted at a reference threshold of 40 and reprocessed at 5 additional threshold values ranging from 35 to 60. Artifact growth rates relative to threshold values were derived using simple linear regressions and then assessed within the context of laser power and duration using Pearson correlations. A total of 33 patients were included, with 28 artifact-containing and 5 artifact-free cases. For artifact-containing cases, a 13% increase in artifact area occurred for every 1-point increase in threshold (R2 > 0.99). Artifact growth rates were not correlated with laser power (r = 0.15, P = .44) or duration (r = 0.0049, P = .98). One of the 5 artifact-free cases developed artifact at a threshold of 60. Artifact generation is likely multifactorial involving tissue properties and software settings. Operators can minimize software-introduced artifact by reducing threshold values.