Molecular and Phenotypic Characterization of the RORB-Related Disorder.

BACKGROUND AND OBJECTIVES: Heterozygous variants in RAR-related orphan receptor B (RORB) have recently been associated with susceptibility to idiopathic generalized epilepsy. However, few reports have been published so far describing pathogenic variants of this gene in patients with epilepsy and intellectual disability (ID). In this study, we aimed to delineate the epilepsy phenotype associated with RORB pathogenic variants and to provide arguments in favor of the pathogenicity of variants. METHODS: Through an international collaboration, we analyzed seizure characteristics, EEG data, and genotypes of a cohort of patients with heterozygous variants in RORB. To gain insight into disease mechanisms, we performed ex vivo cortical electroporation in mouse embryos of 5 selected variants, 2 truncating and 3 missense, and evaluated on expression and quantified changes in axonal morphology. RESULTS: We identified 35 patients (17 male, median age 10 years, range 2.5-23 years) carrying 32 different heterozygous variants in RORB, including 28 single-nucleotide variants or small insertions/deletions (12 missense, 12 frameshift or nonsense, 2 splice-site variants, and 2 in-frame deletions), and 4 microdeletions; de novo in 18 patients and inherited in 10. Seizures were reported in 31/35 (89%) patients, with a median age at onset of 3 years (range 4 months-12 years). Absence seizures occurred in 25 patients with epilepsy (81%). Nineteen patients experienced a single seizure type: absences, myoclonic absences, or absences with eyelid myoclonia and focal seizures. Nine patients had absence seizures combined with other generalized seizure types. One patient had presented with absences associated with photosensitive occipital seizures. Three other patients had generalized tonic-clonic seizures without absences. ID of variable degree was observed in 85% of the patients. Expression studies in cultured neurons showed shorter axons for the 5 tested variants, both truncating and missense variants, supporting an impaired protein function. DISCUSSION: In most patients, the phenotype of the RORB-related disorder associates absence seizures with mild-to-moderate ID. In silico and in vitro evaluation of the variants in our cohort, including axonal morphogenetic experiments in cultured neurons, supports their pathogenicity, showing a hypomorphic effect.

MONOZEB: Long-term observational study of eslicarbazepine acetate monotherapy.

AIM: The aim of the study was to evaluate the effectiveness and tolerability of eslicarbazepine acetate (ESL) when used as monotherapy for 1 year or more in routine clinical use in patients with focal seizures in epilepsy clinics in Spain. METHODS: This is a retrospective, observational, noninterventional study. Eligible patients were aged ≥18 years, had focal seizures, and started on ESL ≥1 year before database closure. Primary endpoint was the following: proportion seizure-free for ≥6 months at 1 and 2 years. Secondary endpoints included retention on ESL monotherapy at 1 and 2 years, seizure frequency change, seizure worsening, and side effects. Other analyses included seizure freedom from baseline to 1 and 2 years and outcomes in special populations. RESULTS: Four hundred thirty-five patients were included (127 on first-line monotherapy and 308 converting to ESL monotherapy): median daily dose was 800 mg at all time points; 63.2% were seizure-free at 1 year, 65.1% at 2 years, and 50.3% for the entire follow-up. Mean duration of ESL monotherapy was 66.7 months; retention was 88.0% at 1 year and 81.9% at 2 years. Mean reduction in seizure frequency was 75.5% at last visit. Over the entire follow-up, seizure worsening was seen in 22 patients (5.1%), side effects in 28.0%, considered severe in 1.8%, and leading to discontinuation in 5.7%. Dizziness, hyponatremia (sodium <135 mEq/l), and somnolence were the most frequent side effects. Outcomes in special populations (patients aged ≥65 years and those with psychiatric history or learning difficulty) were consistent with the overall population. CONCLUSIONS: Patients with focal seizures taking ESL monotherapy had excellent retention, high seizure-free rates, and good tolerability up to 2 years.

Hypoxemia following generalized convulsive seizures: Risk factors and effect of oxygen therapy.

OBJECTIVE: To analyze the factors that determine the occurrence or severity of postictal hypoxemia in the immediate aftermath of a generalized convulsive seizure (GCS). METHODS: We reviewed the video-EEG recordings of 1,006 patients with drug-resistant focal epilepsy included in the REPO2MSE study to identify those with ≥1 GCS and pulse oximetry (SpO2) measurement. Factors determining recovery of SpO2 ≥ 90% were investigated using Cox proportional hazards models. Association between SpO2 nadir and person- or seizure-specific variables was analyzed after correction for individual effects and the varying number of seizures. RESULTS: A total of 107 GCS in 73 patients were analyzed. A transient hypoxemia was observed in 92 GCS (86%). Rate of GCS with SpO2 <70% dropped from 40% to 21% when oxygen was administered early (p = 0.046). Early recovery of SpO2 ≥90% was associated with early administration of oxygen (p = 0.004), absence of postictal generalized EEG suppression (PGES) (p = 0.014), and extratemporal lobe epilepsy (p = 0.001). Lack of early administration of O2 (p = 0.003), occurrence of PGES (p = 0.018), and occurrence of ictal hypoxemia during the focal phase (p = 0.022) were associated with lower SpO2 nadir. CONCLUSION: Postictal hypoxemia was observed in the immediate aftermath of nearly all GCS but administration of oxygen had a strong preventive effect. Severity of postictal hypoxemia was greater in temporal lobe epilepsy and when hypoxemia was already observed before the onset of secondary GCS.

Drug-resistant epilepsy after treatment for childhood acute lymphocytic leukaemia: from focal epilepsy to Lennox-Gastaut syndrome.

Drug-resistant epilepsy, not associated with acute brain complications or central nervous system leukaemic involvement, can develop in patients treated for acute lymphocytic leukaemia during childhood. It has been postulated that this rare complication may be due to CNS oncological treatment neurotoxicity, related to intrathecal drugs, such as methotrexate, and brain radiotherapy. We report four patients who developed drug-resistant epilepsy sometime after receiving treatment for acute lymphocytic leukaemia. All patients were female and received intrathecal methotrexate. One received additional intrathecal cytarabine, and two concomitant brain radiotherapy. Two developed Lennox-Gastaut type syndrome, one multifocal epilepsy, and one focal epilepsy related to a radiotherapy-induced cavernous angioma. The development of drug-resistant epilepsy after treatment for acute lymphocytic leukaemia is a rare complication that may vary, from focal epilepsy to an epileptic encephalopathy. This may appear even years after the treatment has finished and is most likely associated with treatment-related neurotoxicity.