Boricua Founder Variant in FRRS1L Causes Epileptic Encephalopathy With Hyperkinetic Movements.

OBJECTIVE: To describe a founder mutation effect and the clinical phenotype of homozygous FRRS1L c.737_739delGAG (p.Gly246del) variant in 15 children of Puerto Rican (Boricua) ancestry presenting with early infantile epileptic encephalopathy (EIEE-37) with prominent movement disorder. BACKGROUND: EIEE-37 is caused by biallelic loss of function variants in the FRRS1L gene, which is critical for AMPA-receptor function, resulting in intractable epilepsy and dyskinesia. METHODS: A retrospective, multicenter chart review of patients sharing the same homozygous FRRS1L (p.Gly246del) pathogenic variant identified by clinical genetic testing. Clinical information was collected regarding neurodevelopmental outcomes, neuroimaging, electrographic features and clinical response to antiseizure medications. RESULTS: Fifteen patients from 12 different families of Puerto Rican ancestry were homozygous for the FRRS1L (p.Gly246del) pathogenic variant, with ages ranging from 1 to 25 years. The onset of seizures was from 6 to 24 months. All had hypotonia, severe global developmental delay, and most had hyperkinetic involuntary movements. Developmental regression during the first year of life was common (86%). Electroencephalogram showed hypsarrhythmia in 66% (10/15), with many older children evolving into Lennox-Gastaut syndrome. Six patients demonstrated progressive volume loss and/or cerebellar atrophy on brain magnetic resonance imaging (MRI). CONCLUSIONS: We describe the largest cohort to date of patients with epileptic encephalopathy. We estimate that 0.76% of unaffected individuals of Puerto Rican ancestry carry this pathogenic variant due to a founder effect. Children homozygous for the FRRS1L (p.Gly246del) Boricua variant exhibit a very homogenous phenotype of early developmental regression and epilepsy, starting with infantile spasms and evolving into Lennox-Gastaut syndrome with hyperkinetic movement disorder.

A case of 5,10-methenyltetrahydrofolate synthetase deficiency due to biallelic null mutations with novel findings of elevated neopterin and macrocytic anemia.

We describe a case of 5,10-methenyltetrahydrofolate synthetase (MTHFS) deficiency characterized by microcephaly, global developmental delay, epilepsy, and cerebral hypomyelination. Whole exome sequencing (WES) demonstrated homozygosity for the R74X mutation in the MTHFS gene. The patient had the unexpected finding of elevated cerebrospinal fluid (CSF) neopterin. The novel finding of macrocytic anemia in this patient may provide a clue to the diagnosis of this rare neurometabolic disorder.

Outcomes of vagal nerve stimulation in a pediatric population: a single center experience.

OBJECTIVE: To evaluate the efficacy of vagus nerve stimulation (VNS) in pediatric patients with medically refractory epilepsy. METHOD: We reviewed the medical records of 252 consecutive patients who underwent VNS implantation at a single center over a 5-year period. Patients with complete 6- and 12-month follow-up data were included. Analysis was also done across various subgroups including gender, age at implantation, seizure type, abnormal MRI findings pre-implantation, number of medications at baseline, history of SE, and duration of epilepsy. RESULTS: Complete follow-up data were available for 69 patients. Median seizure reduction for these patients was 50% (Q1: 0%; Q3: 73%) at 6 months and 40% (Q1: -25%; Q3: 75%) at 12 months. When stratified by baseline seizure frequency, there was a significant reduction from baseline of 61% at 6 months and 69% at 12 months for patients in the high-baseline frequency group. There were no significant reductions at month 6 or 12 months for the lower-baseline frequency group. Adverse events were reported in 40.6% (28 out of 69 patients). Six patients had the VNS removed for reasons including lack of efficacy and side effects and were excluded from the study group. CONCLUSION: VNS provides significant seizure reduction, in particular in pediatric patients with a higher baseline seizure frequency.

Short-term response of sleep-potentiated spiking to high-dose diazepam in electric status epilepticus during sleep.

We describe the short-term effects of high-dose oral diazepam on sleep-potentiated epileptiform activity in patients with electric status epilepticus during sleep. We enrolled patients treated with high-dose oral bedtime diazepam from 2001-2009. We defined spike percentage as the percentage of 1-second bins containing at least one spike, and calculated it during three randomly selected 5-minute samples of wakefulness throughout the day and during the first 5 minutes of every hour of non-rapid eye movement sleep at night. In this study, patients were considered to demonstrate sleep-potentiated epileptiform activity when their spike percentage during sleep was increased by ≥50% compared with wakefulness. Twenty-nine children (18 boys) were included (median age, 7.4 years). Twenty-four hours after receiving high-dose diazepam, epileptiform activity was significantly reduced (76.7% at baseline vs 40.8% 24 hours after high-dose diazepam; Wilcoxon signed ranks test, Z = -4.287, P < 0.0001). Seven patients (24.1%) manifested mild, reversible side effects during the first 48 hours after diazepam administration. High-dose oral diazepam effectively and safely reduced epileptiform activity in patients with electric status epilepticus during sleep.