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Christel Depienne, Eric LeGuern and colleagues report the identification of 5 de novo missense mutations in HCN1 in individuals with early-onset epileptic encephalopathy. Functional studies confirmed the pathogenic nature of these mutations. Hyperpolarization-activated, cyclic nucleotide–gated (HCN) channels contribute to cationic I h current in neurons and regulate the excitability of neuronal networks. Studies in rat models have shown that the Hcn1 gene has a key role in epilepsy, but clinical evidence implicating HCN1 mutations in human epilepsy is lacking. We carried out exome sequencing for parent-offspring trios with fever-sensitive, intractable epileptic encephalopathy, leading to the discovery of two de novo missense HCN1 mutations. Screening of follow-up cohorts comprising 157 cases in total identified 4 additional amino acid substitutions. Patch-clamp recordings of I h currents in cells expressing wild-type or mutant human HCN1 channels showed that the mutations had striking but divergent effects on homomeric channels. Individuals with mutations had clinical features resembling those of Dravet syndrome with progression toward atypical absences, intellectual disability and autistic traits. These findings provide clear evidence that de novo HCN1 point mutations cause a recognizable early-onset epileptic encephalopathy in humans.

Precision treatments for monogenic epilepsies, i.e. treatments that can at least partially reverse the biochemical consequences of a pathogenic gene variant, have been gradually emerging over the years. To date, however, information on the efficacy of these treatments is mostly based on case-reports and retrospective studies. As a result, utilisation of precision treatments often lack consistency and a pre-defined outcome monitoring plan. N-of-1 strategies in clinical care are pre-defined, individually tailored, repeated challenge-withdrawal therapeutic trials designed to assess the value of a treatment of interest for an individual. Despite their potential to improve clinical decision-making, N-of-1 strategies have been hampered by limited guidance on their implementation and lack of consensus on oversight procedures. To improve treatment selection for rare monogenic epilepsies, the PINPOINT initiative (Precision Treatments In MoNogenic EPilepsies: Observational Registry And N-of-1 Trial Recommendations) was set up as a collaborative effort within the European Reference Network for Rare and Complex Epilepsies. PINPOINT aims to develop recommendations for the design of N-of-1 strategies with off-label precision treatments for monogenic epilepsies. Using available N-of-1 trial manuals, different components of N-of-1 design were tailored to the context of epilepsy and oversight procedures were outlined. These efforts resulted in this guidance document—or blueprint for N-of-1 strategies for monogenic epilepsies in clinical care. This blueprint defines the characteristics of treatments and patients that would be suitable for N-of-1 strategies. Key principles for outcome measure selection, period duration and statistical analysis are defined. Consideration is given to interim assessment rules, which establish whether proceeding onto an additional treatment cycle is likely to provide significant advantages. Procedures for ethical oversight are proposed. This blueprint for N-of-1 strategies can be used as a basis for master protocols to optimise individualised clinical care in a standardised and consistent manner. We are confident that this document will provide physicians with the building blocks needed to elevate precision treatments for rare monogenic epilepsies out of their current landscape of inadequate evidence.

Background Fahr’s disease and syndrome are rare disorders leading to calcification of the small arteries in the basal ganglia of the brain, resulting in a wide range of symptoms comprising cognitive decline, movement disorders and neuropsychiatric symptoms. No disease-modifying therapies are available. Studies have shown the potential of treatment of ectopic vascular calcifications with bisphosphonates. This paper describes the rationale and design of the CALCIFADE trial which evaluates the effects of etidronate in patients with Fahr’s disease or syndrome. Methods The CALCIFADE trial is a randomised, placebo-controlled, double-blind trial which evaluates the effects of etidronate 20 mg/kg during 12 months follow-up in patients aged ≥ 18 years with Fahr’s disease or syndrome. Etidronate and placebo will be administered in capsules daily for two weeks on followed by ten weeks off. The study will be conducted at the outpatient clinic of the University Medical Center Utrecht, the Netherlands. The primary endpoint is the change in cognitive functioning after 12 months of treatment. Secondary endpoints are the change in mobility, neuropsychiatric symptoms, volume of brain calcifications, dependence in activities of daily living, and quality of life. Results Patient recruitment started in April 2023. Results are expected in 2026 and will be disseminated through peer-reviewed journals as well as presentations at national and international conferences. Conclusions Fahr’s disease and syndrome are slowly progressive disorders with a negative impact on a variety of health outcomes. Etidronate might be a new promising treatment for patients with Fahr’s disease or syndrome. Trial registration ClinicalTrials.gov, NCT05662111. Registered 22 December 2022, https://clinicaltrials.gov/ct2/show/NCT01585402 .

Colour agnosia is a disorder that impairs colour knowledge (naming, recognition) despite intact colour perception. Previously, we have identified the first and only-known family with hereditary developmental colour agnosia. The aim of the current study was to explore genomic regions and candidate genes that potentially cause this trait in this family. For three family members with developmental colour agnosia and three unaffected family members CGH-array analysis and exome sequencing was performed, and linkage analysis was carried out using DominantMapper, resulting in the identification of 19 cosegregating chromosomal regions. Whole exome sequencing resulted in 11 rare coding variants present in all affected family members with developmental colour agnosia and absent in unaffected members. These variants affected genes that have been implicated in neural processes and functions ( CACNA2D4 , DDX25 , GRINA , MYO15A ) or that have an indirect link to brain function, development or disease ( MAML2 , STAU1 , TMED3 , RABEPK ), and a remaining group lacking brain expression or involved in non-neural traits ( DEPDC7 , OR1J1 , OR8D4 ). Although this is an explorative study, the small set of candidate genes that could serve as a starting point for unravelling mechanisms of higher level cognitive functions and cortical specialization, and disorders therein such as developmental colour agnosia.

Objective Genetic causes are increasingly identified in patients with focal epilepsy. These genetic causes may be related to the effectiveness of epilepsy surgery. We aimed to assess the use and yield of genetic testing in a large cohort of patients who were evaluated for epilepsy surgery. Methods We performed a retrospective single‐center consecutive cohort study of patients who were evaluated for surgery between 1990 and 2016. Within this cohort, we assessed the use of genetic testing—either before or after presurgical decision‐making. We evaluated genetic results as well as the outcome of presurgical decision‐making and surgery, and compared these end points for different subgroups—especially MRI‐positive vs MRI‐negative patients. Patients with tuberous sclerosis (TSC) and KRIT1 mutations were excluded from analysis. Results Of the 2385 epilepsy patients who were evaluated for surgery, 1280 (54%) received surgical treatment in our center. Of the entire cohort, 325 (14%) underwent genetic testing, comprising 156 of 450 MRI‐negative patients (35%) vs 169 of 1935 MRI‐positive patients (9%). A genetic cause of epilepsy was found in 40 of the 325 patients (12%, 2% of the entire cohort), mainly consisting of mutations in ion channel function and synaptic transmission genes, and mTOR pathway gene mutations. Three of the seven patients with mTOR pathway gene mutations underwent surgery; two achieved complete seizure freedom. One of the 17 patients with germline mutations in ion channel function and synaptic transmission genes received resective surgery but was not rendered seizure‐free; two other patients underwent invasive intracranial EEG‐monitoring before being rejected. Significance This study shows that genetic testing is increasingly applied in focal epilepsy patients who are considered for epilepsy surgery. The diagnostic yield of genetic testing is highest in next generation sequencing techniques, and the outcome of genetic testing assists selecting eligible patients for invasive intracranial monitoring and resective surgery.

To determine the prevalence of Dravet syndrome, an epileptic encephalopathy caused by SCN1A-mutations, often with seizure onset after vaccination, among infants reported with seizures following vaccination. To determine differences in characteristics of reported seizures after vaccination in children with and without SCN1A-related Dravet syndrome. Data were reviewed of 1,269 children with seizures following immunization in the first two years of life, reported to the safety surveillance system of the Dutch national immunization program between 1 January 1997 and 31 December 2006. Selective, prospective follow-up was performed of children with clinical characteristics compatible with a diagnosis of Dravet syndrome. In 21.9% (n = 279) of children, a diagnosis of Dravet syndrome could not be excluded based on available clinical data (median age at follow-up 16 months). Additional follow-up data were obtained in 83.9% (n = 234) of these children (median age 8.5 years). 15 (1.2% of 1,269; 95%CI:0.6 to 1.8%) children were diagnosed with SCN1A-related Dravet syndrome. Of all reported seizures following vaccinations in the first year of life, 2.5% (95%CI:1.3 to 3.6%) were due to SCN1A-related Dravet syndrome, as were 5.9% of reported seizures (95%CI:3.1 to 8.7%) after 2(nd) or 3(rd) DTP-IPV-Hib vaccination. Seizures in children with SCN1A-related Dravet syndrome occurred more often with a body temperature below 38.5°C (57.9% vs. 32.6%, p = 0.020) and reoccurred more often after following vaccinations (26.7% vs. 4.0%, p = 0.003), than in children without a diagnosis of SCN1A-related Dravet Syndrome. Although Dravet syndrome is a rare genetic epilepsy syndrome, 2.5% of reported seizures following vaccinations in the first year of life in our cohort occurred in children with this disorder. Knowledge on the specific characteristics of vaccination-related seizures in this syndrome might promote early diagnosis and indirectly, public faith in vaccination safety.

The recent identification of copy-number variation in the human genome has opened up new avenues for the discovery of positional candidate genes underlying complex genetic disorders, especially in the field of psychiatric disease. One major challenge that remains is pinpointing the susceptibility genes in the multitude of disease-associated loci. This challenge may be tackled by reconstruction of functional gene-networks from the genes residing in these loci. We applied this approach to autism spectrum disorder (ASD), and identified the copy-number changes in the DNA of 105 ASD patients and 267 healthy individuals with Illumina Humanhap300 Beadchips. Subsequently, we used a human reconstructed gene-network, Prioritizer, to rank candidate genes in the segmental gains and losses in our autism cohort. This analysis highlighted several candidate genes already known to be mutated in cognitive and neuropsychiatric disorders, including RAI1, BRD1, and LARGE. In addition, the LARGE gene was part of a sub-network of seven genes functioning in glycobiology, present in seven copy-number changes specifically identified in autism patients with limited co-morbidity. Three of these seven copy-number changes were de novo in the patients. In autism patients with a complex phenotype and healthy controls no such sub-network was identified. An independent systematic analysis of 13 published autism susceptibility loci supports the involvement of genes related to glycobiology as we also identified the same or similar genes from those loci. Our findings suggest that the occurrence of genomic gains and losses of genes associated with glycobiology are important contributors to the development of ASD.

The aim of this study was to describe the epilepsy phenotype in a large international cohort of patients with KBG syndrome and to study a possible genotype-phenotype correlation. We collected data on patients with ANKRD11 variants by contacting University Medical Centers in the Netherlands, an international network of collaborating clinicians, and study groups who previously published about KBG syndrome. All patients with a likely pathogenic or pathogenic ANKRD11 variant were included in our patient cohort and categorized into an \"epilepsy group\" or \"non-epilepsy group\". Additionally, we included previously reported patients with (likely) pathogenic ANKRD11 variants and epilepsy from the literature. We included 75 patients with KBG syndrome of whom 26 had epilepsy. Those with epilepsy more often had moderate to severe intellectual disability (42.3% vs 9.1%, RR 4.6 [95% CI 1.7-13.1]). Seizure onset in patients with KBG syndrome occurred at a median age of 4 years (range 12 months - 20 years), and the majority had generalized onset seizures (57.7%) with tonic-clonic seizures being most common (23.1%). The epilepsy type was mostly classified as generalized (42.9%) or combined generalized and focal (42.9%), not fulfilling the criteria of an electroclinical syndrome diagnosis. Half of the epilepsy patients (50.0%) were seizure free on anti-seizure medication (ASM) for at least 1 year at the time of last assessment, but 26.9% of patients had drug-resistant epilepsy (failure of ≥2 ASM). No genotype-phenotype correlation could be identified for the presence of epilepsy or epilepsy characteristics. Epilepsy in KBG syndrome most often presents as a generalized or combined focal and generalized type. No distinctive epilepsy syndrome could be identified. Patients with KBG syndrome and epilepsy had a significantly poorer neurodevelopmental outcome compared with those without epilepsy. Clinicians should consider KBG syndrome as a causal etiology of epilepsy and be aware of the poorer neurodevelopmental outcome in individuals with epilepsy.

Objectives We ascertained the prevalence of ictal arrhythmias to explain the high rate of sudden unexpected death in epilepsy (SUDEP) in Dravet syndrome (DS). Methods We selected cases with clinical DS, ≥6 years, SCN1A mutation, and ≥1 seizure/week. Home‐based ECG recordings were performed for 20 days continuously. Cases were matched for age and sex to two epilepsy controls with no DS and ≥1 major motor seizure during video‐EEG. We determined the prevalence of peri‐ictal asystole, bradycardia, QTc changes, and effects of convulsive seizures (CS) on heart rate, heart rate variability (HRV), and PR/QRS. Generalized estimating equations were used to account for multiple seizures within subjects, seizure type, and sleep/wakefulness. Results We included 59 cases. Ictal recordings were obtained in 45 cases and compared to 90 controls. We analyzed 547 seizures in DS (300 CS) and 169 in controls (120 CS). No asystole occurred. Postictal bradycardia was more common in controls (n = 11, 6.5%) than cases (n = 4, 0.7%; P = 0.002). Peri‐ictal QTc‐lengthening (≥60ms) occurred more frequently in DS (n = 64, 12%) than controls (n = 8, 4.7%, P = 0.048); pathologically prolonged QTc was rare (once in each group). In DS, interictal HRV was lower compared to controls (RMSSD P = 0.029); peri‐ictal values did not differ between the groups. Prolonged QRS/PR was rare and more common in controls (QRS: one vs. none; PR: three vs. one). Interpretation We did not identify major arrhythmias in DS which can directly explain high SUDEP rates. Peri‐ictal QTc‐lengthening was, however, more common in DS. This may reflect unstable repolarization and an increased propensity for arrhythmias.

Background SCN1A is one of the most important epilepsy‐related genes, with pathogenic variants leading to a range of phenotypes with varying disease severity. Different modifying factors have been hypothesized to influence SCN1A‐related phenotypes. We investigate the presence of rare and more common variants in epilepsy‐related genes as potential modifiers of SCN1A‐related disease severity. Methods 87 patients with SCN1A‐related epilepsy were investigated. Whole‐exome sequencing was performed by the Beijing Genomics Institute (BGI). Functional variants in 422 genes associated with epilepsy and/or neuronal excitability were investigated. Differences in proportions of variants between the epilepsy genes and four control gene sets were calculated, and compared to the proportions of variants in the same genes in the ExAC database. Results Statistically significant excesses of variants in epilepsy genes were observed in the complete cohort and in the combined group of mildly and severely affected patients, particularly for variants with minor allele frequencies of <0.05. Patients with extreme phenotypes showed much greater excesses of epilepsy gene variants than patients with intermediate phenotypes. Conclusion Our results indicate that relatively common variants in epilepsy genes, which would not necessarily be classified as pathogenic, may play a large role in modulating SCN1A phenotypes. They may modify the phenotypes of both severely and mildly affected patients. Our results may be a first step toward meaningful testing of modifier gene variants in regular diagnostics for individual patients, to provide a better estimation of disease severity for newly diagnosed patients. Relatively common variants in epilepsy genes may play a large role in modulating SCN1A‐related phenotypes. They may modify the phenotypes of both severely and mildly affected patients.