mTOR-therapy and targeted treatment opportunities in mTOR-related epilepsies associated with cortical malformations.

Dysregulation of the mTOR pathway is now well documented in several neurodevelopmental disorders associated with epilepsy. Mutations of mTOR pathway genes are involved in tuberous sclerosis complex (TSC) as well as in a range of cortical malformations from hemimegalencephaly (HME) to type II focal cortical dysplasia (FCD II), leading to the concept of "mTORopathies" (mTOR pathway-related malformations). This suggests that mTOR inhibitors (notably rapamycin (sirolimus), and everolimus) could be used as antiseizure medication. In this review, we provide an overview of pharmacological treatments targeting the mTOR pathway for epilepsy based on lectures from the ILAE French Chapter meeting in October 2022 in Grenoble. There is strong preclinical evidence for the antiseizure effects of mTOR inhibitors in TSC and cortical malformation mouse models. There are also open studies on the antiseizure effects of mTOR inhibitors, as well as one phase III study showing the antiseizure effect of everolimus in TSC patients. Finally, we discuss to which extent mTOR inhibitors might have properties beyond the antiseizure effect on associated neuropsychiatric comorbidities. We also discuss a new way of treatment on the mTOR pathways.

Non-pharmacological medical treatment in pediatric epilepsies.

The ketogenic diet is a high-fat, low-protein, low-carbohydrate diet that has been employed as a non-pharmacologic therapy for refractory epilepsy. Several multicenter and two randomized studies have demonstrated the efficacy of the ketogenic diet and the modified Atkins diet for children and adolescent with pharmacoresitant epilepsy. In order to facilitate patient tolerability and palatability, the diet protocols are gradually modified including changes in ratios of the fat versus non-fat components and the initiation of the diet with or without fasting. The modified Atkins diet is now used as an alternative diet. A randomized trial establishing the efficacy of the modified Atkins diet is now available. More recently, the low glycemic index diet seems to be used successfully for pharmacoresistant epilepsy but there are currently only open studies. Looking at the clinical efficacy of dietary treatments, the studies usually report a greater than 50% reduction in seizure frequency in about half of patients at 3 months under diet. Most of the patients who are responders to the ketogenic diet exhibited a decrease in seizure frequency within two months of treatment onset. Efficacy of the ketogenic diet has also been reported for teenager and adult patients. Dietary treatment of epilepsy should not be considered as a last chance treatment. It can be used during the investigation for epilepsy surgery even in case of structural abnormalities. In some epilepsy syndromes such as infantile spasms, myoclonic-astatic epilepsy and refractory status epilepticus, an early use seems helpful. The exact underlying mechanisms are unknown and remain a topic of active research.

[Myoclonic astatic seizures in a child with Sturge-Weber syndrome]. / Crises myoclonoastatiques chez un patient présentant un syndrome de Sturge-Weber.

INTRODUCTION: Sturge-Weber syndrome is a neurocutaneous disease associating facial and pial angioma. Focal epilepsy is a common sign. In a few cases, generalized seizures have been reported. CASE REPORT: We report on a four-year-old girl with Sturge-Weber syndrome. The first focal seizures occurred at three years of age. She developed refractory status epilepticus. At discharge from the PICU, she was on a ketogenic diet and received three antiepileptic drugs. No seizures were observed for four months. The patient then developed several types of seizures: myoclonic seizures, focal clonic seizures, and sudden falls. We were unable to determine the etiology of the falls. Typical myoclonic astatic seizures were identified on video-electroencephalographic recordings. CONCLUSION: Seizures in Sturge-Weber syndrome are usually focal. Four patients with Sturge-Weber syndrome and myoclonoastatic seizures are reported in the literature. We discuss the pathophysiological mechanisms leading from a focal lesion to generalized myoclonoastatic seizures.

Small vessel abnormalities in alternating hemiplegia of childhood: pathophysiologic implications.

BACKGROUND: The pathophysiology of alternating hemiplegia of childhood (AHC) is unclear. The authors evaluated the skin and muscle biopsies from patients with AHC for vascular abnormalities. METHODS: Skin biopsy specimens from four patients ages 18 months, 8 years, 9 years, and 18 years and muscle biopsies from two of these patients were examined by electron microscopy and compared with healthy controls. RESULTS: Vascular abnormalities were found in both skin and muscle. Skin biopsies showed similar abnormalities in all four patients. Vacuoles were visible in the endothelium. The most striking abnormality was the presence in the tunica media of small and unevenly shaped vascular smooth muscle cells (VSMCs) containing intracytoplasmic vacuoles and, occasionally, apoptotic nuclei, with variations according to patient age. Moreover, most VSMCs had lost junctions with neighboring cells, and some were completely isolated. In vessels from muscle biopsies, the VSMCs showed vacuoles, residual osmiophilic deposits, and myofilament loss with substitution by vacuoles. CONCLUSIONS: The vascular abnormalities in our patients suggest a primary or secondary vascular pathophysiology to alternating hemiplegia of childhood. The vascular smooth muscle cells may be the initial target of the disease process.