Epilepsy surgery in tuberous sclerosis complex (TSC): emerging techniques and redefinition of treatment goals

Molecular Neurosurgery: Introduction to Gene Therapy and Clinical Applications

To date, more than 100 clinical trials have used sequence-based therapies to address diseases of the pediatric central nervous system. The first targeted pathologies share common features: the diseases are severe; they are due (mostly) to single variants; the variants are well characterized within the genome; and the interventions are technically feasible. Interventions range from intramuscular and intravenous injection to intrathecal and intraparenchymal infusions. Whether the therapeutic sequence consists of RNA or DNA, and whether the sequence is delivered via simple oligonucleotide, nanoparticle, or viral vector depends on the disease and the involved cell type(s) of the nervous system. While only one active trial targets an epilepsy disorder—Dravet syndrome—experiences with aromatic L-amino acid decarboxylase deficiency, spinal muscular atrophy, and others have taught us several lessons that will undoubtedly apply to the future of gene therapy for epilepsies. Epilepsies, with their diverse underlying mechanisms, will have unique aspects that may influence gene therapy strategies, such as targeting the epileptic zone or nodes in affected circuits, or alternatively finding ways to target nearly every neuron in the brain. This article focuses on the current state of gene therapy and includes its history and premise, the strategy and delivery vehicles most commonly used, and details viral vectors, current trials, and considerations for the future of pediatric intracranial gene therapy.

Minimally Invasive Destructive, Ablative, and Disconnective Epilepsy Surgery

Conventional epilepsy surgery performed by microsurgical dissection typically requires large cranial working windows created with high-speed drills and lengthy incisions. In the past few decades, minimally invasive techniques have been developed with smaller incisions, comparable efficacy, shorter hospitalizations, and better safety profiles. These minimally invasive alternatives utilize stereotactic, ultrasonic, radiotherapeutic, and endoscopic techniques. Although not able to completely replace conventional surgery for all etiologies of epilepsy, these minimally invasive techniques have revolutionized modern epilepsy surgery and have been an invaluable asset to the neurosurgeon's repertoire. The endoscope has allowed for surgeons to have adequate visualization during resective and disconnective epilepsy surgeries using keyhole or miniature craniotomies. Modern stereotactic techniques such as laser interstitial thermal therapy and radiofrequency ablation can be used as viable alternatives for mesial temporal lobe epilepsy and can destroy lesional tissue deep areas without the approach-related morbidity of microsurgery such as with hypothalamic hamartomas. These stereotactic techniques do not preclude future surgery in the settings of treatment failure and have been used successfully after failed conventional surgery. Multiple ablation corridors can be performed in a single procedure that can be used for lesioning of large targets or to simplify treating multifocal epilepsies. These stereotactic techniques have even been used successfully to perform disconnective procedures such as hemispherotomies and corpus callosotomies. In patients unable to tolerate surgery, stereotactic radiosurgery is a minimally invasive option that can result in improved seizure control with minimal procedural risks. Advances in minimally invasive neurosurgery provide viable treatment options for drug-resistant epilepsy with quicker recovery, less injury to functional brain, and for patients that may otherwise not choose conventional surgery.

[Epilepsy surgery in children with tuberous sclerosis]

Most children with tuberous sclerosis (TS) present with intractable seizures. Various factors including demography, clinical data and surgery option are mentioned to affect the outcome after epilepsy surgery in these cases.

OBJECTIVE

To evaluate some demographic and clinical variables probably related to seizure outcome.

MATERIAL AND METHODS

Thirty-three children, median age 4.2 ys (7.5 mths-16 ys), with TS and DR-epilepsy underwent surgery. Within overall 38 procedures (redo surgery was needed in 5 cases), tuberectomy (with or without perituberal cortectomy) was performed in 21 cases, lobectomy - 8, callosotomy - 3, various disconnections (anterior frontal, TPO and hemispherotomy) - 6 patients. Standard preoperative evaluation included MRI and video-EEG. Invasive recordings were used in 8 cases, coupled by MEG and SISCOM SPECT in some cases. ECOG and neuronavigation were used routinely during tuberectomies, and stimulation and mapping were employed in cases with lesions overlapping or near to eloquent cortex. Surgical complications: wound CSF leak (n=1) and hydrocephalus (n=2) were noted in 7.5% of cases. Postoperative neurological deficit (most frequently hemiparesis) developed in 12 patients, being temporary in majority of them. At the last FU (med 5.4 ys) favorable outcome (Engel I) has been achieved in 18 cases (54%), while 7 patients (15%) with persisting seizures reported less common attacks and their milder form (Engel Ib-III). Six patients were able to discontinue AED-treatment and 15 children resumed development and markedly improved in cognition and behavior.

RESULTS AND CONCLUSION

Among different variables potentially influencing the outcome after epilepsy surgery in cases with TS, the most important one is seizure type. If prevalent, focal type may be a biomarker of favorable outcomes and probability to become free of seizures.

An Introduction to Minimally Invasive Pediatric Epilepsy Surgery

The field of minimally invasive surgery has evolved over the past 50 years, including neurosurgery, with an evolution to “minimally invasive neurosurgery” when feasible. Epilepsy surgery has followed this trend, with a transition from standard neurosurgical techniques to minimally invasive techniques in all phases of neurosurgical involvement. These include the diagnostic intracranial electroencephalogram with a subdural exploration to stereoelectroencephalography, the actual resection from an open craniotomy to a less destructive technique, or the multiple modalities of neuromodulation instead of a destructive surgery.

The influence of these minimally invasive techniques has resulted in a change in the overall philosophy of pediatric epilepsy surgery. The expectations of what is considered “successful” epilepsy surgery has changed from total seizure control, in other words, a “cure,” to palliative epilepsy surgery with a decrease in the targeted seizures, especially “disabling seizures.” This has led to an overall greater acceptance of epilepsy surgery. This article summarizes the major reasons behind the explosion of minimally invasive pediatric epilepsy surgery, which are amplified in the subsequent articles. Some of this chapter includes the authors' opinions.

Overview of therapeutic options for epilepsy

Tuberous sclerosis (TSC) epilepsy includes infantile spasms and focal seizures before the age of 2 years, whereas focal seizures are predominant over 2 years and generalized seizures may occasionally be part of Lennox-Gastaut syndrome. The better and earlier the seizure control, the better the child's subsequent cognitive and behavioral prognosis. As for epilepsy of other causes, therapeutic options depend on the type of seizure/epilepsy, age and drug resistance, but there are significant specificities for TSC. (1) As first-line treatment, vigabatrin is unanimously recommended for infantile spasms and focal seizures before 2 years and is also widely used for seizures over 2 years, as are levetiracetam and carbamazepine. (2) If seizures persist (about 40% of children and adolescents), cannabidiol and everolimus, an inhibitor of the mTOR pathway, have recently been approved as adjunctive therapy to the arsenal of antiseizure medications authorized for this age group and to the ketogenic diet. (3) Surgery is an essential treatment option in cases of drug resistance and should be discussed as soon as two treatments have failed. Presurgical investigations and operating techniques have recently progressed spectacularly, for example laser thermocoagulation with stereotactic location. A particularity of TSC is the possibility of sequential interventions on several epileptogenic tubers. (4) Finally, the innovative principle of initiating "pre-seizure" treatment with vigabatrin from the first months of life has just proven effective on the subsequent development of epilepsy in TSC. © 2022 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Multidisciplinary neurocutaneous syndrome clinics: a systematic review and institutional experience

OBJECTIVE

Neurocutaneous syndromes have variable multisystem involvement. The multiorgan involvement, potential pathologies, and various treatment options necessitate collaboration and open discussion to ensure optimal treatment in any given patient. These disorders provide quintessential examples of chronic medical conditions that require a lifelong, multidisciplinary approach. The objectives of this study were to 1) perform a systematic review, thoroughly assessing different multidisciplinary clinic layouts utilized in centers worldwide; and 2) characterize an institutional experience with the management of these conditions, focusing on the patient demographics, clinical presentation, complications, and therapeutic strategies seen in a patient population.

METHODS

A systematic review of studies involving multidisciplinary clinics and their reported structure was performed according to PRISMA guidelines using the PubMed database. Then a retrospective chart review of patients enrolled in the Oklahoma Children’s Hospital Neurocutaneous Syndromes Clinic was conducted.

RESULTS

A search of the PubMed database yielded 251 unique results. Of these, 15 papers were included in the analysis, which identified 16 clinics that treated more than 2000 patients worldwide. The majority of these clinics treated patients with neurofibromatosis (13/16). The remaining clinics treated patients with von Hippel–Lindau syndrome (n = 1), tuberous sclerosis complex (n = 1), and multiple neurocutaneous syndromes (n = 1). The most commonly represented subspecialties in these clinics were genetics (15/16) and neurology (13/16). Five clinics (31%) solely saw pediatric patients, 10 clinics saw a combination of children and adults, and the final clinic had separate pediatric and adult clinics. The retrospective chart review of the Neurocutaneous Syndromes Clinic demonstrated that 164 patients were enrolled and seen in the clinic from April 2013 to December 2021. Diagnoses were made based on clinical findings or results of genetic testing; 115 (70%) had neurofibromatosis type 1, 9 (5.5%) had neurofibromatosis type 2, 35 (21%) had tuberous sclerosis complex, 2 (1%) had von Hippel–Lindau syndrome, 2 (1%) had Gorlin syndrome, and the remaining patient (0.6%) had Aarskog-Scott syndrome. Patient demographics, clinical presentation, complications, and therapeutic strategies are also discussed.

CONCLUSIONS

To the best of the authors’ knowledge, this is the first detailed description of a comprehensive pediatric neurocutaneous clinic in the US that serves patients with multiple syndromes. There is currently heterogeneity between described multidisciplinary clinic structures and practices. More detailed accounts of clinic compositions and practices along with patient data and outcomes are needed in order to establish the most comprehensive and efficient multidisciplinary approach for neurocutaneous syndromes.

Optimization and high-density array of stereoelectroencephalography-guided radiofrequency thermocoagulation for the treatment of pediatric tuberous sclerosis complex with epilepsy

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous syndrome involved in many organ systems. At the same time, epilepsy is the most common manifestation and more than 50% of TSC patients present with intractable epilepsy. This study investigated the efficacy and safety of optimized and high-density stereoelectroencephalography (SEEG) guided radiofrequency thermocoagulation (RF-TC) in treating TSC-related epilepsy.

METHODS

Nine TSC children with refractory epilepsy were treated with first-stage SEEG-Guided RF-TC, and four underwent second-stage-optimized high-density array of SEEG-Guided RF-TC. Patients' clinical data and postoperative outcomes were analyzed retrospectively.

RESULTS

The patients' median age at surgery was 4 years and 2 month (range from 3 years and 5 month to 16 years and 7 month). The mean age at surgery was 6.7 years old. Eight in 9 (88.9%) patients achieved complete remission after the final operation at half-year follow-up. Of seven patients with final postoperative time beyond 1 year, 6 (85.7%) reached completely seizure-free. No severe or long-term neurologic impairment existed in all nine patients.

CONCLUSION

Optimized high-density array of SEEG-guided RF-TC is a safe and highly effective approach and can be an alternative application applied for TSC patients with refractory epilepsy.

Epilepsy Management in Tuberous Sclerosis Complex: Existing and Evolving Therapies and Future Considerations

Tuberous sclerosis complex (TSC) is a rare autosomal dominant condition that affects multiple body systems. Disruption of the mammalian target of rapamycin (mTOR) pathway results in abnormal cell growth, proliferation, protein synthesis, and cell differentiation and migration in TSC. In the central nervous system, mTOR disruption is also believed to influence neuronal excitability and promote epileptogenesis. Epilepsy is the most common neurological manifestation of TSC and affects 80% to 90% of individuals with high rates of treatment resistance (up to 75%). The onset of epilepsy in the majority of individuals with TSC occurs before the age of two years, which is a critical time in neurodevelopment. Both medically refractory epilepsy and early-onset epilepsy are associated with intellectual disability in TSC, while seizure control and remission are associated with lower rates of cognitive impairment. Our current knowledge of the treatment of epilepsy in TSC has expanded immensely over the last decade. Several new therapies such as preemptive vigabatrin therapy in infants, cannabidiol, and mTOR inhibitors have emerged in recent years for the treatment of epilepsy in TSC. This review will provide clinicians with a comprehensive overview of the pharmacological and nonpharmacological therapies available for the treatment of epilepsy related to TSC.

Updated International Tuberous Sclerosis Complex Diagnostic Criteria and Surveillance and Management Recommendations

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disease affecting multiple body systems with wide variability in presentation. In 2013, Pediatric Neurology published articles outlining updated diagnostic criteria and recommendations for surveillance and management of disease manifestations. Advances in knowledge and approvals of new therapies necessitated a revision of those criteria and recommendations.

METHODS

Chairs and working group cochairs from the 2012 International TSC Consensus Group were invited to meet face-to-face over two days at the 2018 World TSC Conference on July 25 and 26 in Dallas, TX, USA. Before the meeting, working group cochairs worked with group members via e-mail and telephone to (1) review TSC literature since the 2013 publication, (2) confirm or amend prior recommendations, and (3) provide new recommendations as required.

RESULTS

Only two changes were made to clinical diagnostic criteria reported in 2013: "multiple cortical tubers and/or radial migration lines" replaced the more general term "cortical dysplasias," and sclerotic bone lesions were reinstated as a minor criterion. Genetic diagnostic criteria were reaffirmed, including highlighting recent findings that some individuals with TSC are genetically mosaic for variants in TSC1 or TSC2. Changes to surveillance and management criteria largely reflected increased emphasis on early screening for electroencephalographic abnormalities, enhanced surveillance and management of TSC-associated neuropsychiatric disorders, and new medication approvals.

CONCLUSIONS

Updated TSC diagnostic criteria and surveillance and management recommendations presented here should provide an improved framework for optimal care of those living with TSC and their families.

Smaller Knife, Fewer Seizures? Recent Advances in Minimally Invasive Techniques in Pediatric Epilepsy Surgery

Children with drug-resistant epilepsy are at high risk for developmental delay, increased mortality, psychiatric comorbidities, and requiring assistance with activities of daily living. Despite the advent of new and effective pharmacologic therapies, about one in 5 children will develop drug-resistant epilepsy, and most of these children continue to have seizures despite trials of other medication. Epilepsy surgery is often a safe and effective option which may offer seizure freedom or at least a significant reduction in seizure burden in many children. However, despite published evidence of safety and efficacy, epilepsy surgery remains underutilized in the pediatric population. Patient and family fears about the risks of surgery may contribute to this gap. Less invasive surgical techniques may be more palatable to children with epilepsy and their caregivers. In this review, we present recent advances in minimally invasive techniques for the surgical treatment of epilepsy as well as intriguing possibilities for the future. We describe the indications for, benefits of, and limits to minimally-invasive techniques including Stereo-encephalography, laser interstitial thermal ablation, deep brain stimulation, focused ultrasound, stereo-encephalography-guided radiofrequency ablation, endoscopic disconnections, and responsive neurostimulation.

Review of the treatment options for epilepsy in tuberous sclerosis complex: towards precision medicine

Tuberous sclerosis complex (TSC) is a rare genetic disorder caused by mutations in the TSC1 or TSC2 genes, which encode proteins that antagonise the mammalian isoform of the target of rapamycin complex 1 (mTORC1) - a key mediator of cell growth and metabolism. TSC is characterised by the development of benign tumours in multiple organs, together with neurological manifestations including epilepsy and TSC-associated neuropsychiatric disorders (TAND). Epilepsy occurs frequently and is associated with significant morbidity and mortality; however, the management is challenging due to the intractable nature of the seizures. Preventative epilepsy treatment is a key aim, especially as patients with epilepsy may be at a higher risk of developing severe cognitive and behavioural impairment. Vigabatrin given preventatively reduces the risk and severity of epilepsy although the benefits for TAND are inconclusive. These promising results could pave the way for evaluating other treatments in a preventative capacity, especially those that may address the underlying pathophysiology of TSC, including everolimus, cannabidiol and the ketogenic diet (KD). Everolimus is an mTOR inhibitor approved for the adjunctive treatment of refractory TSC-associated seizures that has demonstrated significant reductions in seizure frequency compared with placebo, improvements that were sustained after 2 years of treatment. Highly purified cannabidiol, recently approved in the US as Epidiolex® for TSC-associated seizures in patients ⩾1 years of age, and the KD, may also participate in the regulation of the mTOR pathway. This review focusses on the pivotal clinical evidence surrounding these potential targeted therapies that may form the foundation of precision medicine for TSC-associated epilepsy, as well as other current treatments including anti-seizure drugs, vagus nerve stimulation and surgery. New future therapies are also discussed, together with the potential for preventative treatment with targeted therapies. Due to advances in understanding the molecular genetics and pathophysiology, TSC represents a prototypic clinical syndrome for studying epileptogenesis and the impact of precision medicine.