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

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.

Interactions between Triatoma infestans and Triatoma sordida (Hemiptera: Reduviidae) in artificial ecotopes: population growth and age structure

Interaction characteristics between Triatoma infestans Klug, 1834 and Triatoma sordida Stal, 1859 populations were studied in artificial ecotopes for 16 mo. The experimental design involved simultaneous treatments with T. infestans and T. sordida together in the same experimental unit (EU) and each separately in two control units (CU) made of adobe bricks. Chickens were used as host animals. Each unit was dismantled monthly to estimate triatomine population size and age structure, rebuilt, and repopulated with the same insects. In both units, T. infestans population growth followed a logistic model, whereas T. sordida did not show this pattern. T. infestans completed a generation in 24 wk (EU) and 32 wk (CU1), whereas T. sordida did not complete one generation during this period. We concluded that T infestans showed a better colonizing success than T. sordida. After living together for 1 yr, an interference process took place that resulted in the extinction of T. sordida.

[Contribution to knowledge of reservoirs of Trypanosoma cruzi (Chagas, 1909) in Corrientes Province, Argentina]

In order to identify Trypanosoma cruzi reservoirs in transmission areas, 60 mammals in Capital and San Luis del Palmar Departments, Corrientes, Argentina were studied. Primates, rodents, carnivores, marsupials and edentates were investigated, 40 of them living in captivity and 20 caught with traps in a rural area. The mammals were examined by xenodiagnosis and third or fourth instars nymphs of Triatoma infestans starved for 2 weeks were used. The feces were microscopically observed (400x) for Trypanosoma cruzi infection at 30, 60 and 90 days after feeding. Trypanosoma cruzi-like parasites were identified in 2 Saimiri sciureus and 1 Cebus apella analyzed by xenodiagnosis. It was concluded that parasitemia was low. However, the presence in a forest area of Didelphis albiventris, potential reservoir of the parasite, indicates a risk factor and deserves further epidemiological study for a true diagnosis of this endemic infection.

[Clinical cross-sectional and epidemiologic study of Chagas disease in a rural area of the Argentinian northeast]

The main goal was to know the epidemiologic, clinical, electrocardiographic and radiologic characteristics among a population of seropositives and seronegatives to Trypanosoma cruzi in a rural area of the Department of San Miguel, province of Corrientes, Argentina. One hundred and thirty-two patients of different ages: 2-79 years old were researched (58 males, 74 females). In order to make a thorough assessment clinical evaluation and cardiologic testing were carried out. Signs and symptoms consistent with heart disease, blood pressure, 12-lead ECG registry and chest x-ray (PA view) were registered. In signs and symptoms, abnormal ECG patterns and radiologic abnormalities, non-significant statistic difference were observed. Although we were unable to find a significant relationship between chagasic infection and a higher prevalence for heart disease, it is important to stress the fact that 54.0% of the studied population was largely composed of very young patients whose ages were less than 20 years old, and 45.0% of those older than 41 years showed ECG abnormalities.

[Domestic infestation by Triatoma infestans and prevalence of Trypanosoma cruzi seropositives in a rural area of the Argentinian northeast]

An epidemiological study was carried out from April 1991 to December 1993 to obtain a general view of T. cruzi domestic transmission in rural areas of San Miguei Department, Corrientes. From 100 analyzed households, 50.0% was infested by T infestans (Klug, 1834) and 1.0% by T. sordida (Stal, 1859). Domiciliary colonization by T. sordida is reported for first time in Corrientes province. T. cruzi infection of T. infestans was 23.1%. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of anti T. cruzi antibodies in 388 human sera, 23.4% showed serological reactivity. An important high rate (12.9%) was observed in the age group of higher transmission risk. Seropositives percentages increased with age and reached 50.0% in 31-40 years old group. Domestic infestation by T. infestans, seropositive human prevalence to T. cruzi and householders precarious life conditions prove that this endemic disease is still a problem in the studied area.

[Population interactions between Triatoma infestans and Triatoma sordida]

Populations of T. infestans and T. sordida were studied between September 1988 and April 1989 with a view to discovering if any kind of interaction took place between them while they lives together in the same experimental unit and exploited the same food resource (chicken). The initial age structure for each species was: 27 N1, 7 N2, 11 N3, 3 N4, 8 N5, 4 males and 10 females. The population dynamics nutritional status, predation and gregarious behavior were estimated by means of a monthly census. The colonizing success of T. infestans was greater than that of T. sordida in view of the values obtained: fecundity (146 eggs/female), longevity (157.8 days) and mortality (39.4) compared with the values recorded for T. sordida: 118 eggs/female, 81.1 days and 54.0% respectively. The population growth of T. insfestans followed an exponential model, with a high nymphal recruitment rate, while the T. sordida population was early extinguished. In general, the average weight of T. infestans remained close to the initial values while that of T. sordida declined. Gregarious groups were formed principally in the inferior sector of wall 1 (near the host) with a higher aggregation in T. infestans. These results make it possible to propose the hypothesis of the competitive superiority of T. infestans.