Modulation index predicts the effect of ethosuximide on developmental and epileptic encephalopathy with spike-and-wave activation in sleep.

PURPOSE: In developmental and epileptic encephalopathy with spike-and-wave activation in sleep (DEE-SWAS), the thalamocortical network is suggested to play an important role in the pathophysiology of the progression from focal epilepsy to DEE-SWAS. Ethosuximide (ESM) exerts effects by blocking T-type calcium channels in thalamic neurons. With the thalamocortical network in mind, we studied the prediction of ESM effectiveness in DEE-SWAS treatment using phase-amplitude coupling (PAC) analysis. METHODS: We retrospectively enrolled children with DEE-SWAS who had an electroencephalogram (EEG) recorded between January 2009 and September 2022 and were prescribed ESM at Okayama University Hospital. Only patients whose EEG showed continuous spike-and-wave during sleep were included. We extracted 5-min non-rapid eye movement sleep stage N2 segments from EEG recorded before starting ESM. We calculated the modulation index (MI) as the measure of PAC in pair combination comprising one of two fast oscillation types (gamma, 40-80 Hz; ripples, 80-150 Hz) and one of five slow-wave bands (delta, 0.5-1, 1-2, 2-3, and 3-4 Hz; theta, 4-8 Hz), and compared it between ESM responders and non-responders. RESULTS: We identified 20 children with a diagnosis of DEE-SWAS who took ESM. Fifteen were ESM responders. Regarding gamma oscillations, significant differences were seen only in MI with 0.5-1 Hz slow waves in the frontal pole and occipital regions. Regarding ripples, ESM responders had significantly higher MI in coupling with all slow waves in the frontal pole region, 0.5-1, 3-4, and 4-8 Hz slow waves in the frontal region, 3-4 Hz slow waves in the parietal region, 0.5-1, 2-3, 3-4, and 4-8 Hz slow waves in the occipital region, and 3-4 Hz slow waves in the anterior-temporal region. SIGNIFICANCE: High MI in a wider area of the brain may represent the epileptic network mediated by the thalamus in DEE-SWAS and may be a predictor of ESM effectiveness.

Epileptic spasms in clusters without hypsarrhythmia in infancy and childhood: A single age-dependent type of epilepsy or well-defined epileptic syndrome?

OBJECTIVE: In this study, we present the electroclinical features and outcomes of 92 patients with epileptic spasms (ES) in clusters without modified or classical hypsarrhythmia that started in either in infancy or in childhood; we compared both groups in terms of electroclinical features, etiology, treatment, evolution, and outcome. METHODS: Between June 2000 and July 2022, 92 patients met the electroclinical diagnostic criteria of ES in clusters without hypsarrhythmia. Patients with ES associated with other epileptic encephalopathies including West Syndrome, as well as those with the specific etiology of ES and developmental and epileptic encephalopathy associated with CDKL5 were excluded. RESULTS: The patients were divided into two groups based on the age at ES onset: those with ES onset before (Group 1) and those with ES onset after 2 years of age (Group 2). The features of ES and the type of associated seizures before and after ES onset, as well as the interictal and ictal EEG and electromyography findings were similar in both groups. The etiologies were mainly structural (40.2%), genetic (11.9%), and unknown (44.6%) in majority of the patients in both groups. Thirty-one patients were seizure-free, while in the remaining patients the seizures continued. Nine patients (9.8%) with unilateral structural lesions underwent surgery with good results. The neurological abnormalities and developmental findings prior to ES onset depended on the underlying etiology. CONCLUSION: Our series of patients may represent a well-defined epileptic syndrome or type of epilepsy with onset in infancy or childhood characterized by ES in clusters without hypsarrhythmia associated with focal and generalized seizures and EEG paroxysms without neurological deterioration.

The timing of auditory sensory deficits in Norrie disease has implications for therapeutic intervention.

Norrie disease is caused by mutation of the NDP gene, presenting as congenital blindness followed by later onset of hearing loss. Protecting patients from hearing loss is critical for maintaining their quality of life. This study aimed to understand the onset of pathology in cochlear structure and function. By investigating patients and juvenile Ndp-mutant mice, we elucidated the sequence of onset of physiological changes (in auditory brainstem responses, distortion product otoacoustic emissions, endocochlear potential, blood-labyrinth barrier integrity) and determined the cellular, histological, and ultrastructural events leading to hearing loss. We found that cochlear vascular pathology occurs earlier than previously reported and precedes sensorineural hearing loss. The work defines a disease mechanism whereby early malformation of the cochlear microvasculature precedes loss of vessel integrity and decline of endocochlear potential, leading to hearing loss and hair cell death while sparing spiral ganglion cells. This provides essential information on events defining the optimal therapeutic window and indicates that early intervention is needed. In an era of advancing gene therapy and small-molecule technologies, this study establishes Ndp-mutant mice as a platform to test such interventions and has important implications for understanding the progression of hearing loss in Norrie disease.

Two types of early epileptic encephalopathy in a Pitt-Hopkins syndrome patient with a novel TCF4 mutation.

INTRODUCTION: Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by mutations in TCF4. Seizures have been found to vary among patients with PTHS. We report the case of a PTHS patient with a novel missense mutation in the gene TCF4, presenting with two types of early epileptic encephalopathy. CASE REPORT: The patient was a Japanese boy. His first seizure was reported at 17 days of age, with twitching of the left eyelid and tonic-clonic seizures on either side of his body. An ictal electroencephalogram (EEG) showed epileptic discharges arising independently from both hemispheres, occasionally resembling migrating partial seizures of infancy (MPSI) that migrated from one side to the other. Brain magnetic resonance imaging revealed agenesis of the corpus callosum. His facial characteristics included a distinctive upper lip and thickened helices. His seizures were refractory, and psychomotor development was severely delayed. At the age of 10 months, he developed West syndrome with spasms and hypsarrhythmia. After being prescribed topiramate (TPM), his seizures and EEG abnormalities dramatically improved. Also, psychomotor development progressed. Whole-exome sequencing revealed a novel de novo missense mutation in exon 18 (NM_001083962.2:c.1718A > T, p.(Asn573Ile)), corresponding to the basic region of the basic helix-loop-helix domain, which may be a causative gene for epileptic encephalopathy. CONCLUSIONS: To our knowledge, this is the first report of a patient with PTHS treated with TPM, who presented with both MPSI as well as West syndrome. This may help provide new insights regarding the phenotypes caused by mutations in TCF4.

Epilepsy Is Heterogeneous in Early-Life Tuberous Sclerosis Complex.

BACKGROUND: Epilepsy in tuberous sclerosis complex (TSC) typically presents with early onset, multiple seizure types, and intractability. However, variability is observed among individuals. Here, detailed individual data on seizure characteristics collected prospectively during early life were used to define epilepsy profiles in this population. METHODS: Children aged zero to 36 months were followed longitudinally. Caregivers kept daily seizure diaries, including onset and daily counts for each seizure type. Patients with >70% seizure diary completion and >365 diary days were included. Developmental outcomes at 36 months were compared between subgroups. RESULTS: Epilepsy was seen in 124 of 156 (79%) participants. Seizure onset occurred from zero to 29.5 months; 93% had onset before age 12 months. Focal seizures and epileptic spasms were most common. Number of seizures (for median 897 days) ranged from 1 to 9128. Hierarchical clustering based on six metrics of seizure burden (age of onset, total seizures, ratio of seizure days to nonseizure days, seizures per seizure day, and worst seven- and 30-day stretches) revealed two distinct groups with broadly favorable and unfavorable epilepsy profiles. Subpopulations within each group showed clinically meaningful differences in seizure burden. Groups with higher seizure burden had worse developmental outcomes at 36 months. CONCLUSIONS: Although epilepsy is highly prevalent in TSC, not all young children with TSC have the same epilepsy profile. At least two phenotypic subpopulations are discernible based on seizure burden. Early and aggressive treatments for epilepsy in TSC may be best leveraged by targeting specific subgroups based on phenotype severity.

Cerebral visual impairment in CDKL5 deficiency disorder: vision as an outcome measure.

AIM: To characterize the neuro-ophthalmological phenotype of cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) and assess visual acuity as a reproducible, quantitative outcome measure. METHOD: We retrospectively analyzed clinical data from patients with CDD. Complete neuro-ophthalmological assessments, including visual acuity, were evaluated. RESULTS: Of 26 patients (22 females, four males; median age 4y, interquartile range 2y 1mo-7y 10mo), cerebral visual impairment (CVI), defined as visual dysfunction in the absence of ocular or anterior visual pathway abnormalities, was diagnosed in all those over 2 years of age. Ophthalmological examinations revealed nystagmus in 10 patients and strabismus in 24 patients. Visual acuity was measured in 24 patients, by preferential looking in all and by sweep visual evoked potential in 13. Visual acuities were lower than age expectations and demonstrated improvement in the first 3 years. Adjusting for age and sex, average preferential looking visual acuity after 2 years of age was higher in patients with intact mobility than in those who were non-mobile. INTERPRETATION: CVI was observed in patients with CDD. Visual acuity improved over time and correlated with mobility. Visual acuity, as a quantifiable measure of visual function, should be considered as an outcome measure in pre-clinical and clinical studies for CDD. What this paper adds Cerebral visual impairment is highly prevalent in cyclin-dependent kinase-like 5 deficiency disorder (CDD). Visual acuity is a measurable quantitative outcome measure in CDD. Visual acuity in CDD correlates with gross motor ability.

Evaluation of the Modified Atkins Diet for the Treatment of Epileptic Spasms Refractory to Hormonal Therapy: A Randomized Controlled Trial.

OBJECTIVES: We aimed to evaluate the efficacy of the modified Atkins diet in children with epileptic spasms who had failed hormonal therapy. METHODS: Children aged 9 months to 3 years having daily epileptic spasms despite a trial of ACTH or oral prednisolone and 1 additional anticonvulsant medication were enrolled. Children were randomly assigned to receive the modified Atkins diet either immediately or after a delay of 4 weeks. The ongoing anticonvulsant medications were continued unchanged. The primary outcome variable was the proportion of children who achieved spasm freedom as per parental reports at 4 weeks. Secondary outcomes included time to spasm cessation, proportion of children with electroclinical remission, the proportion of children with >50% reduction of spasms at 4 weeks, and adverse effects of the diet. (ClinicalTrials.gov Identifier: NCT03807141). RESULTS: A total of 91 children were enrolled in the study; 46 in the diet group and 45 in the control group. At the end of 4 weeks, 11 children in the diet group were spasm free compared with none in the control group (P ≤ .001). The median time to achieve spasm cessation was 10 days (interquartile range 9-20). Nine of these had resolution of hypsarrhythmia on electroencephalography (EEG). Thirty (65.2%) in the diet group had >50% reduction in spasms, compared with none in the control group (P < .001). The most common side effect was constipation, noted in 34.8% of the children. CONCLUSIONS: The modified Atkins diet was found to be effective and well tolerated in children with epileptic spasms refractory to hormonal therapy.

Evolution of Infantile Spasms to Lennox-Gastaut Syndrome: What Is There to Know?

OBJECTIVE: Children with infantile spasms may develop Lennox-Gastaut syndrome. The diagnostic criteria for Lennox-Gastaut syndrome are vague, and many experts use varying combinations of the following criteria for diagnosis: paroxysmal fast activity on electroencephalography (EEG), slow spike and wave on EEG, developmental delay, multiple seizure types, and nocturnal tonic seizures. Our objective was to determine the prevalence of Lennox-Gastaut syndrome in a high-risk cohort of children with a history of infantile spasms and the characteristics of infantile spasms that were associated with the diagnosis of Lennox-Gastaut syndrome. METHODS: Children with infantile spasms who were diagnosed and treated at Children's Hospital Colorado between 2012 and 2018 were included. Lennox-Gastaut syndrome was defined as having 3 of 5 of the following characteristics: paroxysmal fast activity, slow spike and wave, current developmental delay, multiple seizure types, or tonic seizures. Descriptive statistics were performed using median and interquartile range. Univariable analysis was performed with Pearson chi-square, Fisher exact, or the Kruskal-Wallis test. RESULTS: Ninety-seven children met inclusion criteria, and 36% (35/97) met criteria for Lennox-Gastaut syndrome. Developmental delay and history of seizures prior to the onset of infantile spasms were identified as risk factors for the development of Lennox-Gastaut syndrome (P = .003) as was poor response to first treatment for spasms (P = .004). Children with an unknown etiology of infantile spasms were less likely to develop Lennox-Gastaut syndrome (P = .019). Eighty percent (28/35) of the children who met Lennox-Gastaut syndrome criteria lacked a documented diagnosis. CONCLUSIONS: Thirty-six percent of children with infantile spasms met criteria for Lennox-Gastaut syndrome. Risk factors for development of Lennox-Gastaut syndrome were developmental delay and seizures prior to the onset of infantile spasms and poor response to first treatment for infantile spasms. Children with an unknown etiology of infantile spasms were less likely to develop Lennox-Gastaut syndrome. Eighty percent of the children who met our criteria were not given a documented diagnosis of Lennox-Gastaut syndrome, which highlights the fact that many children may not be receiving a diagnosis of Lennox-Gastaut syndrome. We recommend establishing clear guidelines for the diagnosis of Lennox-Gastaut syndrome to ensure that the diagnosis is being made accurately.

Epileptogenic modulation index and synchronization in hypsarrhythmia of West syndrome secondary to perinatal arterial ischemic stroke.

OBJECTIVE: Perinatal arterial ischemic stroke (PAIS) is associated with epileptic spasms of West syndrome (WS) and long term Focal epilepsy (FE). The mechanism of epileptogenic network generation causing hypsarrhythmia of WS is unknown. We hypothesized that Modulation index (MI) [strength of phase-amplitude coupling] and Synchronization likelihood (SL) [degree of connectivity] could interrogate the epileptogenic network in hypsarrhythmia of WS secondary to PAIS. METHODS: We analyzed interictal scalp electroencephalography (EEG) in 10 WS and 11 FE patients with unilateral PAIS. MI between gamma (30-70 Hz) and slow waves (3-4 Hz) was calculated to measure phase-amplitude coupling. SL between electrode pairs was analyzed in 9-frequency bands (5-delta, theta, alpha, beta, gamma) to examine inter- and intra-hemispheric connectivity. RESULTS: MI was higher in affected hemispheres in WS (p = 0.006); no differences observed in FE. Inter-hemispheric SL of 3-delta, theta, alpha, beta, gamma bands was significantly higher in WS (p < 0.001). In WS, modified Z-Score of intra-hemispheric SL values in 3-delta, theta, alpha, beta and gamma in the affected hemispheres were significantly higher than those in the unaffected hemispheres (p < 0.001) as well as 0.5-4 Hz (p = 0.004). CONCLUSIONS: The significantly higher modulation in affected hemisphere and stronger inter- and intra-hemispheric connectivity generate hypsarrhythmia of WS secondary to PAIS. SIGNIFICANCE: Epileptogenic cortical-subcortical transcallosal networks from affected hemisphere post-PAIS provokes infantile spasms.

A team science approach to discover novel targets for infantile spasms (IS).

Infantile spasms (IS) is a devastating epilepsy syndrome that typically begins in the first year of life. Symptoms consist of stereotypical spasms, developmental delay, and electroencephalogram (EEG) that may demonstrate Hypsarhythmia. Current therapeutic approaches are not always effective, and there is no reliable way to predict which patient will respond to therapy. Given this disorder's complexity and the potential impact of a disease-modifying approach, Citizens United for Research in Epilepsy (CURE) employed a "team science" approach to advance the understanding of IS pathology and explore therapeutic modalities that might lead to the development of new ways to potentially prevent spasms and Hypsarhythmia. This approach was a first-of-its-kind collaborative initiative in epilepsy. The IS initiative funded 8 investigative teams over the course of 1-3 years. Projects included the following: discovery on the basic biology of IS, discovery of novel therapeutic targets, cross-validation of targets, discovery of biomarkers, and prognosis and treatment of IS. The combined efforts of a strong investigative team led to numerous advances in understanding the neural pathways underlying IS, testing of small molecules in preclinical models of IS and generated preliminary data on potential biomarkers. Thus far, the initiative has resulted in over 19 publications and subsequent funding for several investigators. Investigators reported that the IS initiative generally affected their research positively due to its collaborative and iterative nature. It also provided a unique opportunity to mentor junior investigators with an interest in translational research. Learnings included the need for a dedicated project manager and more transparent and real-time communication with investigators. The CURE IS initiative represents a unique approach to fund scientific discoveries on epilepsy. It brought together an interdisciplinary group of investigators-who otherwise would not have collaborated-to find transformative therapies for IS. Learnings from this initiative are being utilized for subsequent initiatives at CURE.

Early 17ß-estradiol treatment reduces seizures but not abnormal behaviour in mice with expanded polyalanine tracts in the Aristaless related homeobox gene (ARX).

Children with severe intellectual disability have an increased prevalence of refractory seizures. Steroid treatment may improve seizure outcomes, but the mechanism remains unknown. Here we demonstrate that short term, daily delivery of an exogenous steroid 17ß-estradiol (40 ng/g) in early postnatal life significantly reduced the number and severity of seizures, but did not improve behavioural deficits, in mice modelling mutations in the Aristaless-related homeobox gene (ARX), expanding the first (PA1) or second (PA2) polyalanine tract. Frequency of observed seizures on handling (n = 14/treatment/genotype) were significantly reduced in PA1 (32% reduction) and more modestly reduced in PA2 mice (14% reduction) with steroid treatment compared to vehicle. Spontaneous seizures were assessed (n = 7/treatment/genotype) at 7 weeks of age coinciding with a peak of seizure activity in untreated mice. PA1 mice treated with steroids no longer present with the most severe category of prolonged myoclonic seizures. Treated PA2 mice had an earlier onset of seizures coupled with a subsequent reduction in seizures later in postnatal life, with a complete absence of any seizures during the analysis at 7 weeks of age. Despite the reduction in seizures, 17ß-estradiol treated mice showed no improvement in behavioural or cognitive outcomes in adulthood. For the first time we show that these deficits due to mutations in Arx are already present before seizure onset and do not worsen with seizures. ARX is a transcription factor and Arx PA mutant mice have deregulated transcriptome profiles in the developing embryonic brain. At postnatal day 10, treatment completion, RNAseq identified 129 genes significantly deregulated (Log2FC > ± 0.5, P-value<0.05) in the frontal cortex of mutant compared to wild-type mice. This list reflects genes deregulated in disease and was particularly enriched for known genes in neurodevelopmental disorders and those involved in signalling and developmental pathways. 17ß-estradiol treatment of mutant mice significantly deregulated 295 genes, with only 23 deregulated genes overlapping between vehicle and steroid treated mutant mice. We conclude that 17ß-estradiol treatment recruits processes and pathways to reduce the frequency and severity of seizures in the Arx PA mutant mice but does not precisely correct the deregulated transcriptome nor improve mortality or behavioural and cognitive deficits.

Electroencephalography complexity in infantile spasms and its association with treatment response.

OBJECTIVE: To investigate the potential of EEG multiscale entropy and complexity as biomarkers in infantile spasms. METHODS: We collected EEG data retrospectively from 16 newly diagnosed patients, 16 age- and gender-matched healthy controls, and 15 drug-resistant patients. The multiscale entropy (MSE) and total EEG complexity before anti-epileptic drug (AED) treatment, before adrenocorticotropic hormone (ACTH) treatment, 14 days after ACTH therapy, and after 6 months of follow-up were calculated. RESULTS: The total EEG complexity of 16 newly diagnosed infantile spasms patients was lower than the 16 healthy controls (median [IQR]: 351.5 [323.1-388.1] vs 461.6 [407.7-583.4]). The total EEG complexity before treatment was higher in the six patients with good response to AED than the 10 patients without response (median [IQR]: 410.0 [388.1-475.0] vs 344.5 [319.6-352.0]). The total EEG complexity before and after 14-days of ACTH therapy was not different between 13 ACTH therapy responders and nine non-responders. After 6-months follow-up, the total EEG complexity of ACTH therapy responders were higher than non-responders (median [IQR]: 598.5 [517.4-623.3] vs 448.6 [347.1-536.3]). CONCLUSIONS: The total EEG complexity before AED and 6 months after ACTH are associated with spasm-freedom. SIGNIFICANCE: The total EEG complexity is a potential biomarker to predict and monitor the treatment effect in infantile spasms.

The severe epilepsy syndromes of infancy: A population-based study.

OBJECTIVE: To study the epilepsy syndromes among the severe epilepsies of infancy and assess their incidence, etiologies, and outcomes. METHODS: A population-based cohort study was undertaken of severe epilepsies with onset before age 18 months in Victoria, Australia. Two epileptologists reviewed clinical features, seizure videos, and electroencephalograms to diagnose International League Against Epilepsy epilepsy syndromes. Incidence, etiologies, and outcomes at age 2 years were determined. RESULTS: Seventy-three of 114 (64%) infants fulfilled diagnostic criteria for epilepsy syndromes at presentation, and 16 (14%) had "variants" of epilepsy syndromes in which there was one missing or different feature, or where all classical features had not yet emerged. West syndrome (WS) and "WS-like" epilepsy (infantile spasms without hypsarrhythmia or modified hypsarrhythmia) were the most common syndromes, with a combined incidence of 32.7/100 000 live births/year. The incidence of epilepsy of infancy with migrating focal seizures (EIMFS) was 4.5/100 000 and of early infantile epileptic encephalopathy (EIEE) was 3.6/100 000. Structural etiologies were common in "WS-like" epilepsy (100%), unifocal epilepsy (83%), and WS (39%), whereas single gene disorders predominated in EIMFS, EIEE, and Dravet syndrome. Eighteen (16%) infants died before age 2 years. Development was delayed or borderline in 85 of 96 (89%) survivors, being severe-profound in 40 of 96 (42%). All infants with EIEE or EIMFS had severe-profound delay or were deceased, but only 19 of 64 (30%) infants with WS, "WS-like," or "unifocal epilepsy" had severe-profound delay, and only two of 64 (3%) were deceased. SIGNIFICANCE: Three quarters of severe epilepsies of infancy could be assigned an epilepsy syndrome or "variant syndrome" at presentation. In this era of genomic testing and advanced brain imaging, diagnosing epilepsy syndromes at presentation remains clinically useful for guiding etiologic investigation, initial treatment, and prognostication.

The phenotypic spectrum of X-linked, infantile onset ALG13-related developmental and epileptic encephalopathy.

OBJECTIVE: Asparagine-linked glycosylation 13 (ALG13) deficiencies have been repeatedly described in the literature with the clinical phenotype of a developmental and epileptic encephalopathy (DEE). Most cases were females carrying the recurrent ALG13 de novo variant, p.(Asn107Ser), with normal transferrin electrophoresis. METHODS: We delineate the phenotypic spectrum of 38 individuals, 37 girls and one boy, 16 of them novel and 22 published, with the most common pathogenic ALG13 variant p.(Asn107Ser) and additionally report the phenotype of three individuals carrying other likely pathogenic ALG13 variants. RESULTS: The phenotypic spectrum often comprised pharmacoresistant epilepsy with epileptic spasms, mostly with onset within the first 6 months of life and with spasm persistence in one-half of the cases. Tonic seizures were the most prevalent additional seizure type. Electroencephalography showed hypsarrhythmia and at a later stage of the disease in one-third of all cases paroxysms of fast activity with electrodecrement. ALG13-related DEE was usually associated with severe to profound developmental delay; ambulation was acquired by one-third of the cases, whereas purposeful hand use was sparse or completely absent. Hand stereotypies and dyskinetic movements including dystonia or choreoathetosis were relatively frequent. Verbal communication skills were absent or poor, and eye contact and pursuit were often impaired. SIGNIFICANCE: X-linked ALG13-related DEE usually manifests as West syndrome with severe to profound developmental delay. It is predominantly caused by the recurrent de novo missense variant p.(Asn107Ser). Comprehensive functional studies will be able to prove or disprove an association with congenital disorder of glycosylation.

Expanding the phenotype of PIGS-associated early onset epileptic developmental encephalopathy.

The phosphatidylinositol glycan anchor biosynthesis class S protein (PIGS) gene has recently been implicated in a novel congenital disorder of glycosylation resulting in autosomal recessive inherited glycosylphosphatidylinositol-anchored protein (GPI-AP) deficiency. Previous studies described seven patients with biallelic variants in the PIGS gene, of whom two presented with fetal akinesia and five with global developmental delay and epileptic developmental encephalopathy. We present the molecular and clinical characteristics of six additional individuals from five families with unreported variants in PIGS. All individuals presented with hypotonia, severe global developmental delay, microcephaly, intractable early infantile epilepsy, and structural brain abnormalities. Additional findings include vision impairment, hearing loss, renal malformation, and hypotonic facial appearances with minor dysmorphic features but without a distinctive facial gestalt. Four individuals died due to neurologic complications. GPI anchoring studies performed on one individual revealed a significant decrease in GPI-APs. We confirm that biallelic variants in PIGS cause vitamin pyridoxine-responsive epilepsy due to inherited GPI deficiency and expand the genotype and phenotype of PIGS-related disorder. Further delineation of the molecular spectrum of PIGS-related disorders would improve management, help develop treatments, and encourage the expansion of diagnostic genetic testing to include this gene as a potential cause of neurodevelopmental disorders and epilepsy.

CDKL5 deficiency in forebrain glutamatergic neurons results in recurrent spontaneous seizures.

OBJECTIVE: Mutations of the cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders characterized by intractable epilepsy, intellectual disability, and autism. Multiple mouse models generated for mechanistic studies have exhibited phenotypes similar to some human pathological features, but none of the models has developed one of the major symptoms affecting CDKL5 deficiency disorder (CDD) patients: intractable recurrent seizures. As disrupted neuronal excitation/inhibition balance is closely associated with the activity of glutamatergic and γ-aminobutyric acidergic (GABAergic) neurons, our aim was to study the effect of the loss of CDKL5 in different types of neurons on epilepsy. METHODS: Using the Cre-LoxP system, we generated conditional knockout (cKO) mouse lines allowing CDKL5 deficiency in glutamatergic or GABAergic neurons. We employed noninvasive video recording and in vivo electrophysiological approaches to study seizure activity in these Cdkl5 cKO mice. Furthermore, we conducted Timm staining to confirm a morphological alteration, mossy fiber sprouting, which occurs with limbic epilepsy in both human and mouse brains. Finally, we performed whole-cell patch clamp in dentate granule cells to investigate cell-intrinsic properties and synaptic excitatory activity. RESULTS: We demonstrate that Emx1- or CamK2α-derived Cdkl5 cKO mice manifest high-frequency spontaneous seizure activities recapitulating the epilepsy of CDD patients, which ultimately led to sudden death in mice. However, Cdkl5 deficiency in GABAergic neurons does not generate such seizures. The seizures were accompanied by typical epileptic features including higher amplitude spikes for epileptiform discharges and abnormal hippocampal mossy fiber sprouting. We also found an increase in spontaneous and miniature excitatory postsynaptic current frequencies but no change in amplitudes in the dentate granule cells of Emx1-cKO mice, indicating enhanced excitatory synaptic activity. SIGNIFICANCE: Our study demonstrates that Cdkl5 cKO mice, serving as an animal model to study recurrent spontaneous seizures, have potential value for the pathological study of CDD-related seizures and for therapeutic innovation.

Neocortical Slow Oscillations Implicated in the Generation of Epileptic Spasms.

OBJECTIVE: Epileptic spasms are a hallmark of severe seizure disorders. The neurophysiological mechanisms and the neuronal circuit(s) that generate these seizures are unresolved and are the focus of studies reported here. METHODS: In the tetrodotoxin model, we used 16-channel microarrays and microwires to record electrophysiological activity in neocortex and thalamus during spasms. Chemogenetic activation was used to examine the role of neocortical pyramidal cells in generating spasms. Comparisons were made to recordings from infantile spasm patients. RESULTS: Current source density and simultaneous multiunit activity analyses indicate that the ictal events of spasms are initiated in infragranular cortical layers. A dramatic pause of neuronal activity was recorded immediately prior to the onset of spasms. This preictal pause is shown to share many features with the down states of slow wave sleep. In addition, the ensuing interictal up states of slow wave rhythms are more intense in epileptic than control animals and occasionally appear sufficient to initiate spasms. Chemogenetic activation of neocortical pyramidal cells supported these observations, as it increased slow oscillations and spasm numbers and clustering. Recordings also revealed a ramp-up in the number of neocortical slow oscillations preceding spasms, which was also observed in infantile spasm patients. INTERPRETATION: Our findings provide evidence that epileptic spasms can arise from the neocortex and reveal a previously unappreciated interplay between brain state physiology and spasm generation. The identification of neocortical up states as a mechanism capable of initiating epileptic spasms will likely provide new targets for interventional therapies. ANN NEUROL 2021;89:226-241.

Sleep problems in Rett syndrome animal models: A systematic review.

Due to the discovery of Rett Syndrome (RTT) genetic mutations, animal models have been developed. Sleep research in RTT animal models may unravel novel neural mechanisms for this severe neurodevelopmental heritable rare disease. In this systematic literature review we summarize the findings on sleep research of 13 studies in animal models of RTT. We found disturbed efficacy and continuity of sleep in all genetically mutated models of mice, cynomolgus monkeys, and Drosophila. Models presented highly fragmented sleep with distinct differences in 24-hr sleep/wake cyclicity and circadian arrhythmicity. Overall, animal models mimic sleep complaints reported in individuals with RTT. However, contrary to human studies, in mutant mice, attenuated sleep delta waves, and sleep apneas in non-rapid eye movement sleep were reported. Future studies may focus on sleep structure and EEG alterations, potential central mechanisms involved in sleep fragmentation and the occurrence of sleep apnea across different sleep stages. Given that locomotor dysfunction is characteristic of individuals with RTT, studies may consider to integrate its potential impact on the behavioral analysis of sleep.