The landscape of epilepsy-related GATOR1 variants.

PURPOSE: To define the phenotypic and mutational spectrum of epilepsies related to DEPDC5, NPRL2 and NPRL3 genes encoding the GATOR1 complex, a negative regulator of the mTORC1 pathway METHODS: We analyzed clinical and genetic data of 73 novel probands (familial and sporadic) with epilepsy-related variants in GATOR1-encoding genes and proposed new guidelines for clinical interpretation of GATOR1 variants. RESULTS: The GATOR1 seizure phenotype consisted mostly in focal seizures (e.g., hypermotor or frontal lobe seizures in 50%), with a mean age at onset of 4.4 years, often sleep-related and drug-resistant (54%), and associated with focal cortical dysplasia (20%). Infantile spasms were reported in 10% of the probands. Sudden unexpected death in epilepsy (SUDEP) occurred in 10% of the families. Novel classification framework of all 140 epilepsy-related GATOR1 variants (including the variants of this study) revealed that 68% are loss-of-function pathogenic, 14% are likely pathogenic, 15% are variants of uncertain significance and 3% are likely benign. CONCLUSION: Our data emphasize the increasingly important role of GATOR1 genes in the pathogenesis of focal epilepsies (>180 probands to date). The GATOR1 phenotypic spectrum ranges from sporadic early-onset epilepsies with cognitive impairment comorbidities to familial focal epilepsies, and SUDEP.

Correction: The landscape of epilepsy-related GATOR1 variants.

The original version of this article contained an error in the spelling of the author Erik H. Niks, which was incorrectly given as Erik Niks. This has now been corrected in both the PDF and HTML versions of the article.

Correction to: The landscape of epilepsy-related GATOR1 variants.

The original version of this Article contained an error in the author list where the corresponding author Stéphanie Baulac was repeated twice. This has now been corrected in the HTML, the PDF was correct at the time of publication.

De novo loss-of-function mutations in CHD2 cause a fever-sensitive myoclonic epileptic encephalopathy sharing features with Dravet syndrome.

Dravet syndrome is a severe epilepsy syndrome characterized by infantile onset of therapy-resistant, fever-sensitive seizures followed by cognitive decline. Mutations in SCN1A explain about 75% of cases with Dravet syndrome; 90% of these mutations arise de novo. We studied a cohort of nine Dravet-syndrome-affected individuals without an SCN1A mutation (these included some atypical cases with onset at up to 2 years of age) by using whole-exome sequencing in proband-parent trios. In two individuals, we identified a de novo loss-of-function mutation in CHD2 (encoding chromodomain helicase DNA binding protein 2). A third CHD2 mutation was identified in an epileptic proband of a second (stage 2) cohort. All three individuals with a CHD2 mutation had intellectual disability and fever-sensitive generalized seizures, as well as prominent myoclonic seizures starting in the second year of life or later. To explore the functional relevance of CHD2 haploinsufficiency in an in vivo model system, we knocked down chd2 in zebrafish by using targeted morpholino antisense oligomers. chd2-knockdown larvae exhibited altered locomotor activity, and the epileptic nature of this seizure-like behavior was confirmed by field-potential recordings that revealed epileptiform discharges similar to seizures in affected persons. Both altered locomotor activity and epileptiform discharges were absent in appropriate control larvae. Our study provides evidence that de novo loss-of-function mutations in CHD2 are a cause of epileptic encephalopathy with generalized seizures.

Biallelic CACNA1A mutations cause early onset epileptic encephalopathy with progressive cerebral, cerebellar, and optic nerve atrophy.

The CACNA1A gene encodes the transmembrane pore-forming alpha-1A subunit of the Cav 2.1 P/Q-type voltage-gated calcium channel. Several heterozygous mutations within this gene, including nonsense mutations, missense mutations, and expansion of cytosine-adenine-guanine repeats, are known to cause three allelic autosomal dominant conditions-episodic ataxia type 2, familial hemiplegic migraine type 1, and spinocerebellar ataxia type 6. An association with epilepsy and CACNA1A mutations has also been described. However, the link with epileptic encephalopathies has emerged only recently. Here we describe two patients, sister and brother, with compound heterozygous mutations in CACNA1A. Exome sequencing detected biallelic mutations in CACNA1A: A missense mutation c.4315T>A (p.Trp1439Arg) in exon 27, and a seven base pair deletion c.472_478delGCCTTCC (p.Ala158Thrfs*6) in exon 3. Both patients were normal at birth, but developed daily recurrent seizures in early infancy with concomitant extreme muscular hypotonia, hypokinesia, and global developmental delay. The brain MRI images showed progressive cerebral, cerebellar, and optic nerve atrophy. At the age of 5, both patients were blind and bedridden with a profound developmental delay. The elder sister died at that age. Their parents and two siblings were heterozygotes for one of those pathogenic mutations and expressed a milder phenotype. Both of them have intellectual disability and in addition the mother has adult onset cerebellar ataxia with a slowly progressive cerebellar atrophy. Compound heterozygous mutations in the CACNA1A gene presumably cause early onset epileptic encephalopathy, and progressive cerebral, cerebellar and optic nerve atrophy with reduced lifespan. © 2016 Wiley Periodicals, Inc.

CDKL5 Gene-Related Epileptic Encephalopathy in Estonia: Four Cases, One Novel Mutation Causing Severe Phenotype in a Boy, and Overview of the Literature.

Cyclin-dependent kinase-like 5 (CDKL5) gene mutations have mainly been found in females with early infantile epileptic encephalopathy (EIEE), severe intellectual disability, and Rett-like features. To date, only 22 boys have been reported, presenting with far more severe phenotypic features. We report the first cases of CDKL5 gene-related EIEE in Estonia diagnosed using panels of epilepsy-associated genes and describe the phenotype-genotype correlations in three male and one female patient. One of the mutations, identified in a male patient, was a novel de novo hemizygous frameshift mutation (NM_003159.2:c.2225_2228del (p.Glu742Afs*41)) in exon 15 of CDKL5. All boys have a more severe phenotype than the female patient. In boys with early onset of seizures and poor development with absent or poor eye contact, CDKL5 gene-related EIEE can be suspected and epilepsy-associated genes should be analyzed for early etiological diagnosis. Early genetic diagnosis would be the cornerstone in personalized treatment in the future.

Resting-State Functional Connectivity and Cognitive Impairment in Children with Perinatal Stroke.

Perinatal stroke is a leading cause of congenital hemiparesis and neurocognitive deficits in children. Dysfunctions in the large-scale resting-state functional networks may underlie cognitive and behavioral disability in these children. We studied resting-state functional connectivity in patients with perinatal stroke collected from the Estonian Pediatric Stroke Database. Neurodevelopment of children was assessed by the Pediatric Stroke Outcome Measurement and the Kaufman Assessment Battery. The study included 36 children (age range 7.6-17.9 years): 10 with periventricular venous infarction (PVI), 7 with arterial ischemic stroke (AIS), and 19 controls. There were no differences in severity of hemiparesis between the PVI and AIS groups. A significant increase in default mode network connectivity (FDR 0.1) and lower cognitive functions (p < 0.05) were found in children with AIS compared to the controls and the PVI group. The children with PVI had no significant differences in the resting-state networks compared to the controls and their cognitive functions were normal. Our findings demonstrate impairment in cognitive functions and neural network profile in hemiparetic children with AIS compared to children with PVI and controls. Changes in the resting-state networks found in children with AIS could possibly serve as the underlying derangements of cognitive brain functions in these children.

Valproic acid-induced pancreatitis in a 15-year-old boy with juvenile myoclonic epilepsy.

Drug-induced acute pancreatitis is a rare condition in childhood, and information about the incidence of valproic acid-induced acute pancreatitis in the pediatric population is scarce. In this clinical case, we report a first documented pediatric case of valproic acid-induced pancreatitis in Estonia. A 15-year-old boy with juvenile myoclonic epilepsy developed acute pancreatitis after 2-month therapy with valproic acid. The symptoms of pancreatitis subsided within 1 week after the discontinuation of treatment with valproic acid. Acute pancreatitis should be suspected in any pediatric patient with gastrointestinal symptoms during valproate treatment.

SLCO5A1 and synaptic assembly genes contribute to impulsivity in juvenile myoclonic epilepsy.

Elevated impulsivity is a key component of attention-deficit hyperactivity disorder (ADHD), bipolar disorder and juvenile myoclonic epilepsy (JME). We performed a genome-wide association, colocalization, polygenic risk score, and pathway analysis of impulsivity in JME (n = 381). Results were followed up with functional characterisation using a drosophila model. We identified genome-wide associated SNPs at 8q13.3 (P = 7.5 × 10-9) and 10p11.21 (P = 3.6 × 10-8). The 8q13.3 locus colocalizes with SLCO5A1 expression quantitative trait loci in cerebral cortex (P = 9.5 × 10-3). SLCO5A1 codes for an organic anion transporter and upregulates synapse assembly/organisation genes. Pathway analysis demonstrates 12.7-fold enrichment for presynaptic membrane assembly genes (P = 0.0005) and 14.3-fold enrichment for presynaptic organisation genes (P = 0.0005) including NLGN1 and PTPRD. RNAi knockdown of Oatp30B, the Drosophila polypeptide with the highest homology to SLCO5A1, causes over-reactive startling behaviour (P = 8.7 × 10-3) and increased seizure-like events (P = 6.8 × 10-7). Polygenic risk score for ADHD genetically correlates with impulsivity scores in JME (P = 1.60 × 10-3). SLCO5A1 loss-of-function represents an impulsivity and seizure mechanism. Synaptic assembly genes may inform the aetiology of impulsivity in health and disease.

Epileptic laughter: 2 case reports.

Two cases of gelastic epilepsy in a 6-year-old girl with attacks of mirthful laughter and a 38-year-old male patient with episodes of laughter without any positive emotions are presented. Temporal lobe epilepsy was diagnosed in the first case and possible frontal lobe epilepsy in the second case. It is concluded that that this rare form of epilepsy can be difficult to diagnose and treat, and can clinically be accompanied by urinary incontinence.

The Birth Prevalence of Spinal Muscular Atrophy: A Population Specific Approach in Estonia.

Background: Rare diseases are an important population health issue and many promising therapies have been developed in recent years. In light of novel genetic treatments expected to significantly improve spinal muscular atrophy (SMA) patients' quality of life and the urgent need for SMA newborn screening (NBS), new epidemiological data were needed to implement SMA NBS in Estonia. Objective: We aimed to describe the birth prevalence of SMA in the years 1996-2020 and to compare the results with previously published data. Methods: We retrospectively analyzed clinical and laboratory data of SMA patients referred to the Department of Clinical Genetics of Tartu University Hospital and its branch in Tallinn. Results: Fifty-seven patients were molecularly diagnosed with SMA. SMA birth prevalence was 1 per 8,286 (95% CI 1 per 6,130-11,494) in Estonia. Patients were classified as SMA type 0 (1.8%), SMA I (43.9%), SMA II (22.8%), SMA III (29.8%), and SMA IV (1.8%). Two patients were compound heterozygotes with an SMN1 deletion in trans with a novel single nucleotide variant NM_000344.3:c.410dup, p.(Asn137Lysfs*11). SMN2 copy number was assessed in 51 patients. Conclusion: In Estonia, the birth prevalence of SMA is similar to the median birth prevalence in Europe. This study gathered valuable information on the current epidemiology of SMA, which can guide the implementation of spinal muscular atrophy to the newborn screening program in Estonia.

Linkage-specific deubiquitylation by OTUD5 defines an embryonic pathway intolerant to genomic variation.

Reversible modification of proteins with linkage-specific ubiquitin chains is critical for intracellular signaling. Information on physiological roles and underlying mechanisms of particular ubiquitin linkages during human development are limited. Here, relying on genomic constraint scores, we identify 10 patients with multiple congenital anomalies caused by hemizygous variants in OTUD5, encoding a K48/K63 linkage-specific deubiquitylase. By studying these mutations, we find that OTUD5 controls neuroectodermal differentiation through cleaving K48-linked ubiquitin chains to counteract degradation of select chromatin regulators (e.g., ARID1A/B, histone deacetylase 2, and HCF1), mutations of which underlie diseases that exhibit phenotypic overlap with OTUD5 patients. Loss of OTUD5 during differentiation leads to less accessible chromatin at neuroectodermal enhancers and aberrant gene expression. Our study describes a previously unidentified disorder we name LINKED (LINKage-specific deubiquitylation deficiency-induced Embryonic Defects) syndrome and reveals linkage-specific ubiquitin cleavage from chromatin remodelers as an essential signaling mode that coordinates chromatin remodeling during embryogenesis.

Trait impulsivity in Juvenile Myoclonic Epilepsy.

OBJECTIVE: Impulsivity is a multidimensional construct that can predispose to psychopathology. Meta-analysis demonstrates an association between response impulsivity and Juvenile Myoclonic Epilepsy (JME), a common genetic generalized epilepsy. Here, we test the hypotheses that trait impulsivity is (i) elevated in JME compared to controls; (ii) moderated by specific seizure characteristics; and (iii) associated with psychiatric adverse effects of antiepileptic drugs (AEDs). METHODS: 322 participants with JME and 126 age and gender-matched controls completed the Barratt's Impulsiveness Scale (BIS-brief) alongside information on seizure history and AED use. We compared group BIS-brief scores and assessed associations of JME BIS-brief scores with seizure characteristics and AED adverse effects. RESULTS: The mean BIS-brief score in JME was 18.1 ± 4.4 compared with 16.2 ± 4.1 in controls (P = 0.0007). Elevated impulsivity was associated with male gender (P = 0.027), frequent absence seizures (P = 0.0004) and lack of morning predominance of myoclonus (P = 0.008). High impulsivity significantly increased the odds of a psychiatric adverse event on levetiracetam (P = 0.036), but not any other psychiatric or somatic adverse effects. INTERPRETATION: Trait impulsivity is elevated in JME and comparable to scores in personality and neurotic disorders. Increased seizure frequency and absence of circadian seizure pattern moderate BIS score, suggesting disruption of both cortico-striatal and thalamocortical networks as a shared mechanism between seizures and impulsivity in JME. These findings warrant consideration of impulsivity as a distinct target of intervention, and as a stratifying factor for AED treatment in JME, and perhaps other types of epilepsy. The role of impulsivity in treatment adherence and psychosocial outcome requires further investigation.

Predictive value of clinical and radiological findings in inflicted traumatic brain injury.

AIMS: The aim of this study is to evaluate the value of early radiological investigations in predicting the long-term neurodevelopmental outcome of infants with inflicted traumatic brain injury (ITBI). METHODS: Clinical and radiological investigations of 24 infants with ITBI were performed during the acute phase of injury (1-3 days), and during the early (4 days up to 3 months) and late (>9 months) postinjury phases. The clinical outcome in survivors (n = 22) was based on the Rankin Disability Scale and the Glasgow Outcome Score. RESULTS: Five out of 24 infants (21%) had a poor neurodevelopmental outcome (death and severe disability), 17 infants (71%) had different developmental problems and 2 infants were normal at the mean age of 62 (54-70) (95% CI) months. A low initial Glasgow Coma Scale score of 8 or below [p < 0.05, OR 13.0 (1.3-133.3)], the development of brain oedema [p < 0.005, OR 13.0 (1.6-773)], focal changes in the basal ganglia during the acute phase [p < 0.01, OR 45 (2.1-937.3)], the development of new intracerebral focal changes early postinjury [p < 0.05, OR 24.1(1.0-559.1)], a decrease in white matter [p < 0.01, OR 33 (1.37-793.4)] and the development of severe atrophy before 3 months postinjury [p < 0.05, OR 24 (11.0-559.1)] were significantly correlated with a poor neurodevelopmental outcome. CONCLUSIONS: Early clinical and radiological findings in ITBI are of prognostic value for neurodevelopmental outcome.

Vehicle-associated closed trauma-induced stroke in a 27-day-old girl.

Birth trauma, but not postnatal trauma, has been recognized as a cause of cerebral infarction in newborns. We report a case of cerebral infarction in a 27-day-old girl after a car accident. During the car accident, the child was properly restrained to the child's safety seat. The patient was admitted to the hospital for observation because of pronounced irritability. There were no focal neurological symptoms on admission. Twenty-eight hours after the accident, the child developed focal tonic-clonic seizures and mild right-sided hemiparesis. The seizures were successfully treated with phenobarbital at a dose of 30 mg per day. Computed tomography and magnetic resonance imagining performed on the second and third days after the accident, respectively, showed subdural hemorrhage in the occipital regions and cerebral ischemia in the left parieto-occipital region. Control imaging 10 days later showed signs of reperfusion. Persistent child irritability after head trauma is one of the indicating factors for performing an emergency computed tomography scan of the head.

Three-year follow-up of a girl with chronic paroxysmal hemicrania.

This is a follow-up report of a girl, 5 years 4 months old, with classic symptoms of chronic paroxysmal hemicrania from the age of 2 years 3 months who had a complete response to indomethacin therapy. The patient suffered from frequent episodes of severe unilateral headaches for 1 year and 10 months before the diagnosis of chronic paroxysmal hemicrania was established. Indomethacin treatment lasted for 2 years and 6 months. During the first year of treatment, several doses of indomethacin were missed, which was followed by immediate return of hemicrania episodes and then quick resolution of symptoms after administration of indomethacin. After 2 years and 6 months of treatment, the parents missed the treatment for 1 week and the episodes did not recur. The treatment was discontinued. The patient was free from pain and off the medication 1 year later.

Low cerebral blood flow velocity and head circumference in infants with severe hypoxic ischemic encephalopathy and poor outcome.

AIMS: To evaluate long-term changes in cerebral blood flow velocity (CBFV) and head circumference in asphyxiated infants. METHODS: CBFV was measured in 83 asphyxiated and 115 healthy term infants in anterior and middle cerebral, basilar and internal carotid artery (ICA) up to the age of 60-149 days. The psychomotor development and head circumference was followed for 18 months. RESULTS. Mean CBFV was increased (p < 0.05) during the first days after asphyxia in infants with severe hypoxic-ischemic encephalopathy (HIE) (n = 25) compared to control group or infants with mild to moderate HIE (n = 58) with maximum values found at the age of 36-71.9 h: in ICA (mean [95% CI]) 31.2 (25.5-36.6) cm/s in severe HIE infants compared to 13.0 (12.2-13.9) cm/s in controls. Decreased (p < 0.0001) mean CBFV developed in severe HIE infants by the age of 21-59 days: in ICA 14.1 (11.5-16.8) cm/s compared to 22.9 (21.4-24.4) cm/s in controls. Infants with severe HIE had similar mean height but lower head circumferences compared to controls (p < 0.05) at the age of 21-59 days. CONCLUSION: The high mean CBFV found in infants with severe HIE during the first days after asphyxia is temporary and low CBFV and head circumference develops by the age of 21-59 days.

Changes in cerebral and visceral blood flow velocities in asphyxiated term neonates with hypoxic-ischemic encephalopathy.

OBJECTIVE: The purpose of this study was to evaluate changes in the Doppler blood flow velocity (BFV) in the cerebral and visceral arteries in asphyxiated term neonates. METHODS: The BFV was measured in 47 asphyxiated and 37 healthy term neonates in the anterior cerebral artery, middle cerebral artery, basilar artery, internal carotid artery, celiac artery (CA), superior mesenteric artery (SMA), and renal artery (RA) up to the age of 60 to 149 days. RESULTS: At the age of 12 to 120 hours after asphyxia, the mean BFV had increased, and the resistive index (RI) had decreased (P < .05) in all cerebral arteries in neonates with severe hypoxic-ischemic encephalopathy (HIE) compared with the control group. In neonates with severe HIE, the mean BFV in the RA had significantly decreased at the age of 3 to 240 hours, and the RI had increased at the age of 24 to 240 hours, normalizing by the age of 21 to 59 days compared with the control group (P < .05). In the SMA, a decreased mean BFV was found in neonates with severe HIE compared with those with mild to moderate HIE only at the age of 24 to 36 hours. In neonates with mild to moderate HIE, the mean BFV had increased in the SMA and CA compared with the control group at the age of 2 to 11.9 hours. CONCLUSIONS: A severe alteration of the cerebral and visceral BFV takes place during the first days after asphyxia in neonates with different severities of HIE.

The incidence of childhood traumatic brain injury in Tartu and Tartu County in Estonia.

BACKGROUND: Traumatic brain injury (TBI) is a major health problem in childhood. Estonia and other Baltic states have the highest trauma-related mortality in the European Union. There are no data on the incidence and causes of TBI for children in Estonia. The aim of this study was to estimate the incidence, structure and main causes of TBI in Tartu and Tartu County. METHODS: The study was carried out at Tartu University Hospital, between January 1, 2001, and December 31, 2005. For inclusion in the study the following criteria had to be fulfilled: age 0-14 years, documented brain trauma and neurological symptoms and residency in Tartu or Tartu County. Over the study period the inclusion criteria were fulfilled in 478 cases [272 boys (57%) and 206 girls (43%)]. RESULTS: The incidence of TBI in childhood in Tartu and Tartu County was 369:100,000 (405:100,000 for boys, 330:100,000 for girls). The incidence was highest among children from 0 to 4 years of age - 566:100,000. The main cause of TBI in all age groups was falling - 63.6%. According to severity, 82% of the cases were mild and 18% were moderate and severe. CONCLUSIONS: There is an urgent need for governmental prevention programs for TBI in children in Estonia.

Long-term neurodevelopmental outcome after perinatal arterial ischemic stroke and periventricular venous infarction.

BACKGROUND: Long-term follow-up data after different vascular types of ischemic perinatal stroke is sparse. Our aim was to study neurodevelopmental outcomes following neonatal and presumed perinatal ischemic middle cerebral artery territory stroke (arterial ischemic stroke, AIS) and periventricular venous infarction (PVI). METHODS: A prospective consecutive cohort of 40 term-born children with perinatal stroke (21 AIS, 19 PVI) was identified through the Estonian Paediatric Stroke Database. While 48% of the children with AIS were diagnosed during the neonatal period, all the children with PVI had presumed perinatal stroke. Outcomes based on the Paediatric Stroke Outcome Measure (PSOM) and Kaufman Assessment Battery for Children - Second Edition (K-ABC-II), in relation to extent and laterality of stroke, were defined. RESULTS: At a median age of 7 years 6 months (range 3.6-13y), there was a trend towards worse neurodevelopmental outcome in participants with AIS when compared to PVI (mean total PSOM scores 3.1 and 2.2, respectively; p = 0.06). Combined deficits of motor, language and cognitive/behavioural functions were significantly more common among children with AIS (90%) when compared to children with PVI (53%, p = 0.007). General cognitive ability (by K-ABC-II) was significantly lower in the AIS subgroup (mean 79.6; 95% CI 72.3-87.0), but children with PVI (91.6; 95% CI 85.5-97.8) also had poorer performance than the age-equivalent normative mean. Large extent of stroke was associated with poorer neurodevelopmental outcome and lower cognitive performance in children following AIS but not in PVI. CONCLUSION: In this national cohort, poor long-term neurodevelopmental outcome after perinatal ischemic stroke was seen irrespective of the vascular type or time of diagnosis of stroke. However, the spectrum of neurological deficits is different after perinatal AIS and PVI, with combined deficits more common among children following AIS.