Comparison of angle-to-angle distance and corneal diameter in pediatric eyes using ultrasound biomicroscopy.

OBJECTIVE: To investigate the relationship between corneal diameter and internal corneal span determined from angle-to-angle distance using ultrasound biomicroscopy (UBM) in an observational cross-sectional patient population comprised of 54 eyes (28 healthy control eyes, ages 0.1 to 11.3 years; 26 eyes with primary congenital glaucoma, ages 0.1 to 3.5 years) from 41 pediatric participants ages 0.1 to 11.3 years (mean age: 3±3 years, median age: 2 years). METHODS: Forty cornea photographs with reference ruler and 110 UBM images were obtained. Three observers measured horizontal and vertical corneal diameter and angle-to-angle distance in each cornea photo and UBM image using ImageJ and the average values were used. Main outcome measures were Pearson correlation coefficient, linear regression, mean difference between corneal diameter and angle-to-angle distance, and intra-class correlation coefficients among measurements from all three observers for each parameter. RESULTS: Corneal diameter and angle-to-angle distance had a strong positive correlation horizontally (Pearson r = 0.89, p<0.001) and vertically (r = 0.93, p<0.001). Correlation was consistent regardless of presence of primary congenital glaucoma and participant age. Regression analysis demonstrated a linear relationship between the parameters for horizontal (CD = 0.99*AA+0.28, R2 = 0.81, p<0.001) and vertical (CD = 0.91 *AA+1.32, R2 = 0.85, p<0.001) dimensions. Overall, reliability was good-excellent, ranging from an ICC of 0.76 for vertical corneal diameter to 0.90 for horizontal angle-to-angle distance. CONCLUSIONS: Based on the strong positive correlation found between corneal diameter and angle-to-angle distance in our study population, UBM image analysis can be used to accurately estimate corneal diameter from angle-to-angle distance in children with healthy eyes and primary congenital glaucoma. UBM may provide a useful intraocular alternative for estimating corneal diameter and monitoring diseases that affect the cornea in infants and children, such as congenital glaucoma.

Biallelic inherited SCN8A variants, a rare cause of SCN8A-related developmental and epileptic encephalopathy.

OBJECTIVE: Monoallelic de novo gain-of-function variants in the voltage-gated sodium channel SCN8A are one of the recurrent causes of severe developmental and epileptic encephalopathy (DEE). In addition, a small number of de novo or inherited monoallelic loss-of-function variants have been found in patients with intellectual disability, autism spectrum disorder, or movement disorders. Inherited monoallelic variants causing either gain or loss-of-function are also associated with less severe conditions such as benign familial infantile seizures and isolated movement disorders. In all three categories, the affected individuals are heterozygous for a SCN8A variant in combination with a wild-type allele. In the present study, we describe two unusual families with severely affected individuals who inherited biallelic variants of SCN8A. METHODS: We identified two families with biallelic SCN8A variants by diagnostic gene panel sequencing. Functional analysis of the variants was performed using voltage clamp recordings from transfected ND7/23 cells. RESULTS: We identified three probands from two unrelated families with DEE due to biallelic SCN8A variants. Each parent of an affected individual carried a single heterozygous SCN8A variant and exhibited mild cognitive impairment without seizures. In both families, functional analysis demonstrated segregation of one allele with complete loss-of-function, and one allele with altered biophysical properties consistent with partial loss-of-function. SIGNIFICANCE: These studies demonstrate that SCN8A DEE may, in rare cases, result from inheritance of two variants, both of which exhibit reduced channel activity. In these families, heterozygosity for the dominant variants results in less severe disease than biallelic inheritance of two variant alleles. The clinical consequences of variants with partial and complete loss of SCN8A function are variable and likely to be influenced by genetic background.

Prax330 reduces persistent and resurgent sodium channel currents and neuronal hyperexcitability of subiculum neurons in a mouse model of SCN8A epileptic encephalopathy.

SCN8A epileptic encephalopathy is a severe genetic epilepsy syndrome caused by de novo gain-of-function mutations of SCN8A encoding the voltage-gated sodium (Na) channel (VGSC) NaV1.6. Therapeutic management is difficult in many patients, leading to uncontrolled seizures and risk of sudden unexpected death in epilepsy (SUDEP). There is a need to develop novel anticonvulsants that can specifically target aberrant VGSC activity associated with SCN8A gain-of-function mutations. In this study, we investigate the effects of Prax330, a novel VGSC inhibitor, on the biophysical properties of wild-type (WT) NaV1.6 and the patient mutation p.Asn1768Asp (N1768D) in ND7/23 cells. The effects of Prax330 on persistent (INaP) and resurgent (INaR) Na currents and neuronal excitability in subiculum neurons from a knock-in mouse model of the Scn8a-N1768D mutation (Scn8aD/+) were also examined. In ND7/23 cells, Prax330 reduced INaP currents recorded from cells expressing Scn8a-N1768D and hyperpolarized steady-state inactivation curves. Recordings from brain slices demonstrated elevated INaP and INaR in subiculum neurons from Scn8aD/+ mutant mice and abnormally large action potential (AP) burst-firing events in a subset of neurons. Prax330 (1 µM) reduced both INaP and INaR and suppressed AP bursts, with a smaller effect on AP waveforms that had similar morphology to WT neurons. Prax330 (1 µM) also reduced synaptically-evoked APs in Scn8aD/+ subiculum neurons but not in WT neurons. Our results highlight the efficacy of targeting INaP and INaR and inactivation parameters in controlling subiculum excitability and suggest Prax330 as a promising novel therapy for SCN8A epileptic encephalopathy.

High sensitivity detection of HIV-1 using two genomic targets compared with single target PCR.

The genetic diversity of Human Immunodeficiency Virus type-1(HIV-1) has been shown to affect the performance of Nucleic Acid Testing (NAT) of Human Immunodeficiency Virus type-1. Although, majority NAT assays were designed to detect the conserved regions of HIV-1 mutations at the primer or probe binding regions may lead to false negatives. In this study, we evaluated the feasibility of detecting two genomic targets for enhanced sensitivity. A total of 180 tests using HIV-1 VQA RNA quantitation standard, 240 tests using EQAPOL HIV-1 viral diversity subtype panel, and 30 clinical plasma samples from Cameroon were evaluated. The analysis was based on probit and hit rate. The genomic targets LOD estimated by PROBIT for the gag target was 118 cps/ml (95%CI 64 cps/ml lower bound), Pol or POL/LTR was at 40 cps/ml (95%CI 17, 16 cps/ml), LTR 45 cps/ml (95%CI 20 cps/ml lower bound), and Gag/LTR at 67.8 cps/ml (95%CI 32 cps/ml lower bound). For HIV-1 subtypes the overall reactivity was 55-100% when tested at 100 and 1000 cps/ml and combination of genomic targets detection increased the reactivity to 100%. The plasma samples evaluation showed LTR or pol/LTR combination yielded higher sensitivity for patients with lower viral load (<40 cps/ml). We conclude that detection of two HIV-1 genomic targets improved sensitivity for detection of genetically diverse HIV-1 strains.