Corpus callosotomy performed with laser interstitial thermal therapy

The changing landscape of palliative epilepsy surgery for Lennox Gastaut Syndrome

Lennox Gastaut Syndrome (LGS) is characterized by drug-resistant epilepsy that typically leads to decreased quality of life and deleterious neurodevelopmental comorbidities from medically refractory seizures. In recent years there has been a dramatic increase in the development and availability of novel treatment strategies for Lennox Gastaut Syndrome patient to improve seizure. Recent advances in neuromodulation and minimally invasive magnetic resonance guided laser interstitial thermal therapy (MRgLITT) have paved the way for new treatments strategies including deep brain stimulation (DBS), responsive neurostimulation (RNS), and MRgLITT corpus callosum ablation. These new strategies offer hope for children with drug-resistant generalized epilepsies, but important questions remain about the safety and effectiveness of these new approaches. In this review, we describe the opportunities presented by these new strategies and how each treatment strategy is currently being employed. Next, we will critically assess available evidence for these new approaches compared to traditional palliative epilepsy surgery approaches, such as vagus nerve stimulation (VNS) and open microsurgical corpus callosotomy (CC). Finally, we will describe future directions that would help define which of the available strategies should be employed and when.

A multi-center comparison of surgical techniques for corpus Callosotomy in pediatric drug-resistant epilepsy

OBJECTIVES

Corpus callosotomy (CC) is used to reduce seizures, primarily in patients with generalized drug-resistant epilepsy (DRE). The invasive nature of the procedure contributes to underutilization despite its potential superiority to other palliative procedures. The goal of this study was to use a multi-institutional epilepsy surgery database to characterize the use of CC across participating centers.

METHODS

Data were acquired from the Pediatric Epilepsy Research Consortium (PERC) Surgery Database, a prospective observational study collecting data on children 0-18 years referred for surgical evaluation of DRE across 22 U.S. pediatric epilepsy centers. Patient, epilepsy, and surgical characteristics were collected across multiple CC modalities. Outcomes and complications were recorded and analyzed statistically.

RESULTS

Eighty-three patients undergoing 85 CC procedures at 14 participating epilepsy centers met inclusion criteria. Mean age at seizure onset was 2.3 years (0-9.4); mean age for Phase I evaluation and surgical intervention were 9.45 (.1-20) and 10.46 (.2-20.6) years, respectively. Generalized seizure types were the most common (59%). Complete CC was performed in 88%. The majority of CC procedures (57%) were via open craniotomy, followed by laser interstitial thermal therapy (LiTT) (20%) and mini-craniotomy/endoscopic (mc/e) (22%). Mean operative times were significantly longer for LiTT, whereas mean estimated blood loss was greater in open cases. Complications occurred in 11 cases (13%) and differed significantly between surgical techniques (p < .001). There was no statistically significant difference in length of postoperative stay across approaches. Mean follow-up was 12.8 months (range 1-39). Favorable Engel outcomes were experienced by 37 (78.7%) of the patients who underwent craniotomy, 10 (58.8%) with LiTT, and 12 (63.2%) with mc/e; these differences were not statistically significant.

SIGNIFICANCE

CC is an effective surgical modality for children with DRE. Regardless of surgical modality, complication rates are acceptable and seizure outcomes generally favorable. Newer, less-invasive, surgical approaches may lead to increased adoption of this efficacious therapeutic option for pediatric DRE.

Novel Surgical Approaches in Childhood Epilepsy: Laser, Brain Stimulation, and Focused Ultrasound

Pediatric epilepsy has a worldwide prevalence of approximately 1% (Berg et al., Handb Clin Neurol 111:391-398, 2013) and is associated with not only lower quality of life but also long-term deficits in executive function, significant psychosocial stressors, poor cognitive outcomes, and developmental delays (Schraegle and Titus, Epilepsy Behav 62:20-26, 2016; Puka and Smith, Epilepsia 56:873-881, 2015). With approximately one-third of patients resistant to medical control, surgical intervention can offer a cure or palliation to decrease the disease burden and improve neurological development. Despite its potential, epilepsy surgery is drastically underutilized. Even today only 1% of the millions of epilepsy patients are referred annually for neurosurgical evaluation, and the average delay between diagnosis of Drug Resistant Epilepsy (DRE) and surgical intervention is approximately 20 years in adults and 5 years in children (Solli et al., Epilepsia 61:1352-1364, 2020). It is still estimated that only one-third of surgical candidates undergo operative intervention (Pestana Knight et al., Epilepsia 56:375, 2015). In contrast to the stable to declining rates of adult epilepsy surgery (Englot et al., Neurology 78:1200-1206, 2012; Neligan et al., Epilepsia 54:e62-e65, 2013), rates of pediatric surgery are rising (Pestana Knight et al., Epilepsia 56:375, 2015). Innovations in surgical approaches to epilepsy not only minimize potential complications but also expand the definition of a surgical candidate. In this chapter, three alternatives to classical resection are presented. First, laser ablation provides a minimally invasive approach to focal lesions. Next, both central and peripheral nervous system stimulation can interrupt seizure networks without creating permanent lesions. Lastly, focused ultrasound is discussed as a potential new avenue not only for ablation but also modulation of small, deep foci within seizure networks. A better understanding of the potential surgical options can guide patients and providers to explore all treatment avenues.

Corpus Callosotomy Is a Safe and Effective Procedure for Medically Resistant Epilepsy

Corpus callosotomy (CC) is an effective surgical treatment for medically resistant generalized or multifocal epilepsy (MRE). The premise of CC extrapolates from the observation that the corpus callosum is the predominant commissural pathway that allows spread and synchroneity of epileptogenic activity between the hemispheres. Candidacy for CC is typically reserved for patients seeking palliative epilepsy treatment with the goal of reducing the frequency of drop attacks, although reduction of other seizure semiologies (absence, complex partial seizures, and tonic-clonic) has been observed. A reduction in morbidity affiliated with evolution of surgical techniques to perform CC has improved the safety profile of the procedure without necessarily sacrificing efficacy.

Completion of disconnective surgery for refractory epilepsy in pediatric patients using robot-assisted MRI-guided laser interstitial thermal therapy

OBJECTIVE

Since 2007, the authors have performed 34 hemispherotomies and 17 posterior quadrant disconnections (temporoparietooccipital [TPO] disconnections) for refractory epilepsy at Sant Joan de Déu Barcelona Children's Hospital. Incomplete disconnection is the main cause of surgical failure in disconnective surgery, and reoperation is the treatment of choice. In this study, 6 patients previously treated with hemispherotomy required reoperation through open surgery. After the authors' initial experience with real-time MRI-guided laser interstitial thermal therapy (MRIgLITT) for hypothalamic hamartomas, they decided to use this technique instead of open surgery to complete disconnective surgeries. The objective was to report the feasibility, safety, and efficacy of MRIgLITT to complete hemispherotomies and TPO disconnections for refractory epilepsy in pediatric patients.

METHODS

Eight procedures were performed on 6 patients with drug-resistant epilepsy. Patient ages ranged between 4 and 18 years (mean 10 ± 4.4 years). The patients had previously undergone hemispherotomy (4 patients) and TPO disconnection (2 patients) at the hospital. The Visualase system assisted by a Neuromate robotic arm was used. The ablation trajectory was planned along the residual connection. The demographic and epilepsy characteristics of the patients, precision of the robot, details of the laser ablation, complications, and results were prospectively collected.

RESULTS

Four patients underwent hemispherotomy and 2 underwent TPO disconnection. Two patients, including 1 who underwent hemispherotomy and 1 who underwent TPO disconnection, received a second laser ablation because of persistent seizures and connections after the first treatment. The average precision of the system (target point localization error) was 1.7 ± 1.4 mm. The average power used was 6.58 ± 1.53 J. No complications were noted. Currently, 5 of the 6 patients are seizure free (Engel class I) after a mean follow-up of 20.2 ± 5.6 months.

CONCLUSIONS

According to this preliminary experience, laser ablation is a safe method for complete disconnective surgeries and allowed epilepsy control in 5 of the 6 patients treated. A larger sample size and longer follow-up periods are necessary to better assess the efficacy of MRIgLITT to complete hemispherotomy and TPO disconnection, but the initial results are encouraging.

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

BACKGROUND

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).

OBSERVATIONS

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.

LESSONS

Complete laser callosotomy is achievable and is a safe alternative to microsurgical or endoscopic approaches.

Decision-making in stereotactic epilepsy surgery

Surgery can cure or significantly improve both the frequency and the intensity of seizures in patients with medication-refractory epilepsy. The set of diagnostic and therapeutic interventions involved in the path from initial consultation to definitive surgery is complex and includes a multidisciplinary team of neurologists, neurosurgeons, neuroradiologists, and neuropsychologists, supported by a very large epilepsy-dedicated clinical architecture. In recent years, new practices and technologies have emerged that dramatically expand the scope of interventions performed. Stereoelectroencephalography has become widely adopted for seizure localization; stereotactic laser ablation has enabled more focal, less invasive, and less destructive interventions; and new brain stimulation devices have unlocked treatment of eloquent foci and multifocal onset etiologies. This article articulates and illustrates the full framework for how epilepsy patients are considered for surgical intervention, with particular attention given to stereotactic approaches.

Surgical Treatment of Drug-Resistant Generalized Epilepsy

PURPOSE OF REVIEW

To summarize current evidence and recent developments in the surgical treatment of drug-resistant generalized epilepsy.

RECENT FINDINGS

Current surgical treatments of drug-resistant generalized epilepsy include vagus nerve stimulation (VNS), deep brain stimulation (DBS) and corpus callosotomy (CC). Neurostimulation with VNS and/or DBS has been shown to be effective in reducing seizure frequency in patients with generalized epilepsy. DBS for generalized epilepsy is primarily consisted of open-loop stimulation directed at the centromedian (CM) nucleus in the thalamus, though closed-loop stimulation and additional targets are being explored. CC can be effective in treating some seizure types and can be performed using traditional surgical techniques or with the less invasive methods of laser ablation and radiosurgery. This current literature supports the use of VNS, DBS and CC, alone or in combination, as palliative treatments of drug-resistant generalized epilepsy.

Stereotactic laser interstitial thermal therapy for the treatment of pediatric drug-resistant epilepsy: indications, techniques, and safety

BACKGROUND

MRI-guided laser interstitial thermal therapy (MRgLITT) is a promising alternative to open surgery for treatment of drug-resistant epilepsy, offering significant advantages over traditional approaches for candidate patients, including minimally invasive approach, shorter hospitalization, and decreased patient post-operative discomfort. LITT uses a stereotactically placed fiber optic laser probe to ablate tissue under real-time MR thermometry.

METHODS

Retrospective chart review of intraoperative and perioperative characteristics was performed for 28 cases of MRgLITT in 25 pediatric patients, ages 4-21 years old, at our institution between 2019 and 2021. MRgLITT ablation of the mesial temporal lobe was performed in 8 cases, extratemporal epileptogenic foci in 9 cases, and for corpus callosotomy in 11 cases.

RESULTS

At 1 year of follow-up, 53% of all patients experienced improvement in seizure frequency (Engel I or II) (class I: 38%, class II: 15%, class III: 17%, class IV: 31%), including 37% of MTL ablations and 80% extratemporal SOZ ablations. After MRgLITT corpus callosotomy, 71% of patients were free from atonic seizures at most recent follow-up. Median length of hospitalization was 2 days (1-3), including a median ICU stay of 1 day (1-2).

CONCLUSION

This series demonstrates the safety of MRgLITT as an approach for seizure control in drug-resistant epilepsy. We provide additional evidence that MRgLITT is an effective procedure that is well-tolerated by pediatric patients and is accompanied by an acceptable rate of complications and relatively short hospital stay.

Surgical nuances in corpus callosotomy as a palliative epilepsy surgery

Background:

Corpus callosotomy is a well-established palliative procedure in selected patients with drug resistant epilepsy (DRE). It has a beneficial role in ameliorating generalized seizures mainly drop attacks. Here, we present some technical tips for performing callosotomy depending on the anatomical basis, to minimize craniotomy size and guard against inadvertently entering the lateral ventricles.

Methods:

This study was a retrospective review of patients who received corpus callosotomy at our institute as a palliative epilepsy surgery. We present our experience and surgical tips with the extraventricular technique of corpus callosotomy with comparison of surgery-related complications and operative time between extraventricular and conventional techniques in selected patients with DRE.

Results:

Our study included 34 patients. First group of patients included 14 patients who received conventional approach, while the extraventricular approach was done in 20 patients. Extraventricular approach showed significantly lower wound complications rate of 10% compared to 78% in intraventricular approach (P < 0.001). Mean operative time was significantly lower in extraventricular versus conventional technique with 52 min versus 94 min, respectively (P < 0.001). Planned extent of corpus callosotomy resection was achieved in all our patients using both approaches.

Conclusion:

The cleft of the septum pellucidum offers a natural pursuit to section corpus callosum strictly midline and completely extraventricular in well selected patients of DRE candidate for callosotomy. Performing corpus callosotomy in extraventricular approach provided better patients outcomes regarding surgery and wound-related complications when compared to conventional approach.

Stereotactic laser interstitial thermal therapy corpus callosotomy for the treatment of pediatric drug-resistant epilepsy

Objective

Corpus callosotomy is a safe and effective procedure for reducing the frequency of drop attacks. MR‐guided laser interstitial thermal therapy (MRgLITT) offers a minimally invasive alternative to conventional open craniotomy for callosotomy. We hypothesized that MRgLITT callosotomy could be safely performed in pediatric patients with similar seizure control.

Methods

We present an institutional case series of 11 procedures in 10 patients for the treatment of drop attacks in drug‐refractory primary generalized epilepsy. MRgLITT was used for complete callosotomy, anterior two‐thirds, posterior, or ablation of residual callosal fibers following prior callosotomy (open or MRgLITT). We retrospectively reviewed clinical course, operative details, radiographic imaging, clinical outcomes, and complications.

Results

Operative time ranged from 4‐8 hours, and median hospitalization was 2 days. No complications were encountered. Among the 7 patients with at least 3 months of follow‐up, 71% experienced freedom from drop attacks at longest follow‐up and 57% of cases showed improvement in their other seizure semiologies as well (Engel Class II: 28%, Class III: 28%, Class IV: 43%).

Significance

MR‐guided LITT callosotomy is safe and effective modality in the management of pediatric patients with medically intractable epilepsy characterized by drop attacks. While this is among the largest pediatric series to date, further studies are required to delineate its safety and efficacy among such patients.

Using a Robotic-Assisted Approach for Stereotactic Laser Ablation Corpus Callosotomy: A Technical Report

BACKGROUND

Corpus callosotomy for medically intractable epilepsy is an effective ablative procedure traditionally achieved using either standard open craniotomy or with less-invasive approaches. Advances in robotic-assisted stereotactic guidance for neurosurgery can be applied for LITT for corpus callosotomy.

CLINICAL PRESENTATIONS

Two patients were included in this study. One was a 25-year-old female patient with extensive bi-hemispheric malformations of cortical development and medically refractory epilepsy, and the other was an 18-year-old male with medically refractory epilepsy and atonic seizures, who underwent a complete corpus callosotomy using robotic-assisted stereotactic guidance for LITT.

RESULTS

Both patients underwent successful intended corpus callosotomy with volumetric analysis demonstrating a length disconnection of 74% and a volume disconnection of 55% for patient 1 and a length disconnection of 83% and a volume disconnection of 33% for patient 2. Postoperatively, both patients had clinical reductions in seizure.

CONCLUSION

Our experience demonstrates that robotic guidance systems can safely and effectively be adapted for minimally invasive LITT corpus callosotomy.

Emerging indications for stereotactic laser interstitial thermal therapy in pediatric neurosurgery

Surgical treatment of deep or difficult to access lesions represents a unique and significant challenge for pediatric neurosurgeons. The introduction of stereotactic magnetic resonance-guided laser interstitial thermal therapy (LITT) over the last decade has had a dramatic impact on the landscape of pediatric neurosurgery. LITT provides a safe and effective option for children with epilepsy from hypothalamic hamartoma that represents a ground-breaking new therapy for a condition which was historically very difficult to treat with previous neurosurgical techniques. LITT has also been used as an alternative surgical technique for mesial temporal sclerosis, focal cortical dysplasia, MR-negative epilepsy, cavernoma-related epilepsy, insular epilepsy, and corpus callosotomy among other epilepsy etiologies. In some cases, LITT has been associated with improved cognitive outcomes compared to standard techniques, as in mesial temporal lobe epilepsy. Initial experiences with LITT for neuro-oncologic processes are also promising. LITT is often attractive to patients and providers as a minimally invasive approach, but the differences in safety and clinical outcome between LITT and traditional approaches are still being studied. In this review, we examine the emerging indications and clinical evidence for LITT in pediatric neurosurgery.

Retrospective analysis of open surgical versus laser interstitial thermal therapy callosotomy in pediatric patients with refractory epilepsy

OBJECTIVE

Corpus callosotomy remains an established surgical treatment for certain types of medically refractory epilepsy in pediatric patients. While the traditional surgical approach is often well tolerated, the advent of MR-guided laser interstitial thermal therapy (LITT) provides a new opportunity to ablate the callosal body in a minimally invasive fashion and minimize the risks associated with an open interhemispheric approach. However, the literature is sparse regarding the comparative efficacy and safety profiles of open corpus callosotomy (OCC) and LITT callosotomy. To this end, the authors present a novel retrospective analysis comparing the efficacy and safety of these methods.

METHODS

Patients who underwent OCC and LITT callosotomy during the period from 2005 to 2018 were included in a single-center retrospective analysis. Patient demographic and procedural variables were collected, including length of stay, procedural blood loss, corticosteroid requirements, postsurgical complications, and postoperative disposition. Pre- and postoperative seizure frequency (according to seizure type) were recorded.

RESULTS

In total, 19 patients, who underwent 24 interventions (16 OCC and 8 LITT), were included in the analysis. The mean follow-up durations for the OCC and LITT cohorts were 83.5 months and 12.3 months, respectively. Both groups experienced reduced frequencies of seizure and drop attack frequency postoperatively. Additionally, LITT callosotomy was associated with a significant decrease in estimated blood loss and decreased length of pediatric ICU stay, with a trend of shorter length of hospitalization.

CONCLUSIONS

Longer-term follow-up and a larger population are required to further delineate the comparative efficacies of LITT callosotomy and OCC for the treatment of pediatric medically refractory epilepsy. However, the authors' data demonstrate that LITT shows promise as a safe and effective alternative to OCC.

Expanding the Treatment Landscape for Lennox-Gastaut Syndrome: Current and Future Strategies

Lennox-Gastaut syndrome (LGS), a childhood-onset severe developmental and epileptic encephalopathy (DEE), is an entity that encompasses a heterogenous group of aetiologies, with no single genetic cause. It is characterised by multiple seizure types, an abnormal EEG with generalised slow spike and wave discharges and cognitive impairment, associated with high morbidity and profound effects on the quality of life of patients and their families. Drug-refractory seizures are a hallmark and treatment is further complicated by its multiple morbidities, which evolve over the patient's lifetime. This review provides a comprehensive overview of the current and future options for the treatment of seizures associated with LGS. Six treatments are specifically indicated as adjunct therapies for the treatment of seizures associated with LGS in the US: lamotrigine, clobazam, rufinamide, topiramate, felbamate and most recently cannabidiol. These therapies have demonstrated reductions in drop seizures in 15%-68% of patients across trials, with responder rates (≥ 50% reduction in drop seizures) of 37%-78%. Valproate is still the preferred first-line treatment, generally in combination with lamotrigine or clobazam. Other treatments frequently used off-label include the broad spectrum anti-epileptic drugs (AED) levetiracetam, zonisamide and perampanel, while recent evidence from observational studies has indicated that a newer AED, the levetiracetam analogue brivaracetam, may be effective and well tolerated in LGS patients. Other treatments in clinical development include fenfluramine in late phase III, perampanel, soticlestat-OV953/TAK-953, carisbamate and ganaxolone. Non-pharmacologic interventions include the ketogenic diet, vagus nerve stimulation and surgical interventions; these are also expanding, with the potential for less invasive techniques for corpus callosotomy that have promise for reducing complications. However, despite these advancements, patients continue to experience a significant burden. Because LGS is not a single entity, tailoring of treatment is needed as opposed to a 'one size fits all' approach. Further research is needed into the underlying aetiologies and pathophysiology of LGS, together with advancements in treatments that encompass the spectrum of seizures associated with this complex syndrome.

Laser Interstitial Thermal Therapy Case Series: Choosing the Correct Number of Fibers Depending on Lesion Size

BACKGROUND

Laser interstitial thermal therapy (LITT) is being used for the treatment of recurrent glioblastoma multiforme (GBM). Lesions can be treated using 1 or multiple LITT fibers depending on the preference of surgeons. Usually, more fibers are needed for coverage of larger tumors.

OBJECTIVE

To investigate and analyze how tumor size affected the number of LITT fibers used.

METHODS

This is a retrospective review of patients undergoing treatment of recurrent GBM. Patients were treated with up to 4 LITT fibers for adequate tumor coverage. Patient demographics, tumor characteristics, length of stay, complications, and biopsy results were recorded.

RESULTS

A total of 43 cases were treated using LITT, and of these cases, 31 consisted of contiguous lesions. We used more fibers to treat larger tumor volumes. On average, for each 5 cc of tumor volume, a fiber was added for proper coverage (P = .554). Complications and length of stay were similar across the groups (P = .378, P = .941).

CONCLUSION

LITT can be used for the treatment of recurrent GBM. For each 5 cc of tumor volume, a LITT fiber can be added to the treatment plan.