Progressive Worsening of Gait and Motor Abnormalities in Older Adults With Dravet Syndrome

Spotlight on mechanism of sudden unexpected death in epilepsy in Dravet syndrome

Dravet syndrome (DS) is a severe and catastrophic epilepsy with childhood onset. The incidence and prevalence of sudden unexpected death in epilepsy (SUDEP) are significantly higher in DS patients than in general epileptic populations. Although extensive research conducted, the underlying mechanisms of SUDEP occurring in DS patients remain unclear. This review focuses on the link between DS and SUDEP and analyzes the potential pathogenesis. We summarize the genetic basis of DS and SUDEP and elucidate the pathophysiological mechanisms of SUDEP in DS. Furthermore, given the drug-resistant nature of this disorder, the pharmacological approach has limited efficacy and often causes side effects, therefore, the non-pharmacological approaches and precise treatment can reduce the risk of SUDEP in this condition, open a new window to cure this disease, and provide a widened landscape of treatment options for patients.

Variants in ATP6V0C are associated with Dravet-like developmental and epileptic encephalopathy

OBJECTIVE

Dravet syndrome (DS) is a developmental and epileptic encephalopathy. Diagnosis is clinical, but ~90% of patients have pathogenic variants in SCN1A. ATP6V0C has recently been proposed as a novel candidate gene for epilepsy, with or without developmental delay. Here we describe two adult patients with a clinical diagnosis of DS associated with ATP6V0C variants.

METHODS

Patients with developmental and epileptic encephalopathies were evaluated by physicians who are experts in DS, and their clinical diagnosis was correlated with genetic findings. A subgroup of those patients with DS but without known genetic causes were evaluated through gene panels, whole exome sequencing, and chromosome microarray. Phenotype was determined by pediatric and adult chart reviews, interviews, and physical examinations.

RESULTS

Of 753 patients with DS, two unrelated individuals with classic features of DS during childhood and adulthood were identified with heterozygous de novo missense variants in ATP6V0C (c.319G > C, p.(Gly107Arg) and c.284C > T, p.(Ala95Val), respectively). Both variants were absent in normal populations and computational prediction algorithms suggested deleterious effects on protein structure and/or function. No disease-causing variants in other genes previously associated with DS were found.

SIGNIFICANCE

Here we describe two adult patients with Dravet-like syndrome and pathogenic/likely pathogenic variants in ATP6V0C. We propose that abnormal ATP6V0C function can, at the severe end of the clinical spectrum, be associated with Dravet-like phenotype. This is relevant, as these patients would not qualify for disease-modifying antisense nucleotide or gene therapies targeting SCN1A.

The natural history of CDKL5 deficiency disorder into adulthood

Knowledge of the natural history of CDKL5 deficiency disorder (CDD) is limited to the results of cross-sectional analysis of largely pediatric cohorts. Assessment of outcomes in adulthood is critical for clinical decision-making and future precision medicine approaches but is challenging because of the diagnostic gap and duration of follow-up that would be required for prospective studies. We aimed to delineate the natural history retrospectively from adulthood. We analyzed clinical data about an international cohort of 67 adults with CDD. We analyzed demographic, phenotypic, CDKL5 Developmental Score (CDS), and treatment data, and tested associations with genetic factors, sex, and a positive or negative history of neonatal seizures, as an early predictor of prognosis. All but one of 67 adults (55 females, median age of 24 years at last follow-up) had epilepsy, typically beginning with epileptic spasms or tonic seizures before 4 months of age. Focal-onset and non-motor seizures emerged later. Fewer than a third had been documented as having bilateral tonic-clonic seizures or status epilepticus. Seizures often improved with age, but 73% had never experienced more than 6 months of seizure-freedom. Clobazam, sodium valproate, and lamotrigine were the most frequently prescribed antiseizure medications, but no specific treatment demonstrated superiority. Common comorbidities included movement disorders, visual impairment, sleep disorders, constipation, and scoliosis. All participants had intellectual disability, 75% had not acquired speech and 45% had regressed developmentally. 16% never achieved any CDS skill, but most attained at least three, and 28% attained six or all seven. By adulthood, half of those who had achieved any CDS skill retained all their CDS skills. The skills most frequently lost were independent walking and standing. Those with a history of neonatal seizures tended to attain fewer CDS skills and were more likely to have abnormal muscle tone in adulthood, atrioventricular conduction delay, and potential complications of their illness and treatment. Individuals carrying missense variants attained more CDS skills than those with other variants and were more likely to lose skills in adulthood and develop anxiety, possibly reflecting the limited neurodevelopment of those with non-missense variants, who manifested a more multisystemic disorder. In summary, retrospective data from adulthood elucidates the evolution of symptoms, variation in developmental outcomes, and the treatment landscape in CDKL5 deficiency disorder. Presence a non-missense variants or a history of neonatal seizures indicates a more complex disorder and lower developmental trajectory. Our findings will inform management decisions, prognostication, and the design of clinical trials in CDKL5 Deficiency Disorder.

Medial septum parvalbumin-expressing inhibitory neurons are impaired in a mouse model of Dravet Syndrome

Dravet syndrome (DS) is a severe neurodevelopmental disorder caused by pathogenic variants in the SCN1A gene, which encodes the voltage-gated sodium channel Na v 1.1 α subunit. Experiments in animal models of DS - including the haploinsufficient Scn1a +/- mouse - have identified impaired excitability of interneurons in the hippocampus and neocortex; this is thought to underlie the treatment-resistant epilepsy that is a prominent feature of the DS phenotype. However, additional brain structures, such as the medial septum (MS), also express SCN1A . The medial septum is known to play an important role in cognitive function and thus may contribute to the intellectual impairment that also characterizes DS. In this study, we employed whole cell patch clamp recordings in acute brain slices to characterize the electrophysiological properties of MS neurons in Scn1a +/- mice versus age-matched wild-type littermate controls. We found no discernible genotype-related differences in MS cholinergic (ChAT) neurons, but significant dysfunction within MS parvalbumin-expressing (PV) inhibitory neurons in Scn1a +/- mice. We further identified heterogeneity of firing patterns among MS PV neurons, and additional genotype differences in the proportion of subtype representation. These results confirm that the MS is an additional locus of pathology in DS, that may contribute to co- morbidities such as cognitive impairment.

Effect of levodopa on pathological gait in Dravet syndrome: A randomized crossover trial using three-dimensional gait analysis

OBJECTIVE

Individuals with Dravet syndrome (DS) exhibit progressive gait disturbance. No quantitative studies have been conducted to evaluate the effectiveness of medication for gait disturbance. Therefore, the aim of this study was to evaluate the effectiveness of levodopa for pathological gait in people with DS using three-dimensional gait analysis (3DGA).

METHODS

Nine individuals with DS, ages 6-20 years, participated in a crossover study of levodopa and were randomly assigned to the levodopa precedence or no levodopa precedence group. Levodopa/carbidopa hydrate was prescribed at a dose of 5 mg/kg/day (body weight <60 kg) or 300 mg/day (body weight ≥60 kg). The medication was taken for 4-6 weeks (4-week washout period). 3DGA was performed three times before the study, with and without levodopa. A mixed-effects model was used to evaluate the effectiveness of levodopa. The primary outcome was the change in the Gait Deviation Index (GDI). In addition, spatiotemporal gait parameters, 6-minute walking distance (6MD), and balance were evaluated. The correlation between the effectiveness of levodopa and age or gait performance before starting levodopa was analyzed.

RESULTS

Levodopa improved the GDI by 4.2 points, (p = .029), 6MD by 52 m (p = .002), and balance test result by 4.1 mm (p = .011) in participants with DS. No severe adverse events were observed, with the exception of one participant, who exhibited fever and consequently stopped taking levodopa. Levodopa was more effective in younger participants with a higher baseline gait performance.

SIGNIFICANCE

Our randomized crossover trial showed that levodopa has the potential to improve gait disturbance in people with DS.

Epileptic seizures worsen the gait and motor abnormalities in adult patients with Dravet syndrome (with a case report and literature review)

Dravet syndrome (DS), previously known as severe myoclonic epilepsy in infancy (SMEI), is considered the most serious "epileptic encephalopathy." Here, we present a man with a de novo SCN1A mutation who was diagnosed with DS at the age of 29. In addition to pharmaco-resistant seizures and cognitive delay, he also developed moderate to severe motor and gait problems, such as crouching gait and Pisa syndrome. Moreover, it deteriorated significantly following an epileptic seizure. The patient presented with severe flexion of the head and trunk in the sagittal plane and fulfilled the diagnostic criteria for camptocormia and antecollis. After a week, it spontaneously alleviated partially. We applied levodopa to the patient and had a good response. Functional Gait Assessment (FGA) was assessed at three different times: 4 days after the seizure, 1 week after the seizure, and after taking levodopa for 2 years. The results were 4, 12, and 19 points, respectively. We postulated that: (1) gait and motor deficits are somehow influenced by recurrent epileptic episodes;(2) the nigrostriatal dopamine system is involved. To our knowledge, we were the ones who first reported this phenomenon.

Dravet syndrome: A systematic literature review of the illness burden

We performed a systematic literature review and narrative synthesis according to a pre-registered protocol (Prospero: CRD42022376561) to identify the evidence associated with the burden of illness in Dravet syndrome (DS), a developmental and epileptic encephalopathy characterized by drug-resistant epilepsy with neurocognitive and neurobehavioral impairment. We searched MEDLINE, Embase, and APA PsychInfo, Cochrane's database of systematic reviews, and Epistemonikos from inception to June 2022. Non-interventional studies reporting on epidemiology (incidence, prevalence, and mortality), patient and caregiver health-related quality of life (HRQoL), direct and indirect costs and healthcare resource utilization were eligible. Two reviewers independently carried out the screening. Pre-specified data were extracted and a narrative synthesis was conducted. Overall, 49 studies met the inclusion criteria. The incidence varied from 1:15 400-1:40 900, and the prevalence varied from 1.5 per 100 000 to 6.5 per 100 000. Mortality was reported in 3.7%-20.8% of DS patients, most commonly due to sudden unexpected death in epilepsy and status epilepticus. Patient HRQoL, assessed by caregivers, was lower than in non-DS epilepsy patients; mean scores (0 [worst] to 100/1 [best]) were 62.1 for the Kiddy KINDL/Kid-KINDL, 46.5-54.7 for the PedsQL and 0.42 for the EQ-5D-5L. Caregivers, especially mothers, were severely affected, with impacts on their time, energy, sleep, career, and finances, while siblings were also affected. Symptoms of depression were reported in 47%-70% of caregivers. Mean total direct costs were high across all studies, ranging from $11 048 to $77 914 per patient per year (PPPY), with inpatient admissions being a key cost driver across most studies. Mean costs related to lost productivity were only reported in three publications, ranging from approximately $19 000 to $20 000 PPPY ($17 596 for mothers vs $1564 for fathers). High seizure burden was associated with higher resource utilization, costs and poorer HRQoL. The burden of DS on patients, caregivers, the healthcare system, and society is profound, reflecting the severe nature of the syndrome. Future studies will be able to assess the impact that newly approved therapies have on reducing the burden of DS.

Adult Phenotype of SYNGAP1-DEE

Background and Objectives

SYNGAP1 variants are associated with rare developmental and epileptic encephalopathies (DEEs). Although SYNGAP1-related childhood phenotypes are well characterized, the adult phenotype remains ill-defined. We sought to investigate phenotypes and outcomes in adults with SYNGAP1 variants and epilepsy.

Methods

Patients 18 years or older with DEE carrying likely pathogenic and pathogenic (LP/P) SYNGAP1 variants were recruited through physicians' practices and patient organization groups. We used standardized questionnaires to evaluate current seizures, medication use, sleep, gastrointestinal symptoms, pain response, gait, social communication disorder and adaptive skills of patients. We also assessed caregiver burden.

Results

Fourteen unrelated adult patients (median: 21 years, range: 18-65 years) with SYNGAP1-DEE were identified, 11 with novel and 3 with known LP/P SYNGAP1 de novo variants. One patient with a partial exon 3 deletion had greater daily living skills and social skills than others with single-nucleotide variants. Ten of 14 (71%) patients had drug-resistant seizures, treated with a median of 2 antiseizure medications. All patients (100%) had abnormal pain processing. Sleep disturbances, social communication disorders, and aggressive/self-injurious behaviors were each reported in 86% of patients. Only half of adults could walk with minimal or no assistance. Toileting was normal in 29%, and 71% had constipation. No adult patients could read or understand verbal material at a sixth-grade level or higher. Aggressive/self-injurious behaviors were leading cause of caregiver burden. The oldest patient was aged 65 years; although nonambulant, she had walked independently when younger.

Discussion

Seventy-one percent of patients with SYNGAP1-DEEs continue to have seizures when adults. Nonseizure comorbidities, especially aggression and self-injurious behaviors, are major management challenges in adults with SYNGAP1-DEE. Only 50% of adults can ambulate with minimal or no assistance. Almost all adult patients depend on caregivers for many activities of daily living. Prompt diagnostic genetic testing of adults with DEE can inform clinical care and guide outcomes of precision therapies.

Morphometry and network-based atrophy patterns in SCN1A-related Dravet syndrome

Mutations of the voltage-gated sodium channel SCN1A gene (MIM#182389) are among the most clinically relevant epilepsy-related genetic mutations and present variable phenotypes, from the milder genetic epilepsy with febrile seizures plus to Dravet syndrome, a severe developmental and epileptic encephalopathy. Qualitative neuroimaging studies have identified malformations of cortical development in some patients and mild atrophic changes, partially confirmed by quantitative studies. Precise correlations between MRI findings and clinical variables have not been addressed. We used morphometric methods and network-based models to detect abnormal brain structural patterns in 34 patients with SCN1A-related epilepsy, including 22 with Dravet syndrome. By measuring the morphometric characteristics of the cortical mantle and volume of subcortical structures, we found bilateral atrophic changes in the hippocampus, amygdala, and the temporo-limbic cortex (P-value < 0.05). By correlating atrophic patterns with brain connectivity profiles, we found the region of the hippocampal formation as the epicenter of the structural changes. We also observed that Dravet syndrome was associated with more severe atrophy patterns with respect to the genetic epilepsy with febrile seizures plus phenotype (r = -0.0613, P-value = 0.03), thus suggesting that both the underlying mutation and seizure severity contribute to determine atrophic changes.

Epilepsy genetics: a practical guide for adult neurologists

An understanding of epilepsy genetics is important for adult neurologists, as making a genetic diagnosis gives clinical benefit. In this review, we describe the key features of different groups of genetic epilepsies. We describe the common available genetic tests for epilepsy, and how to interpret them.

Measuring the inch stones for progress: Gross motor function in the developmental and epileptic encephalopathies

OBJECTIVE

Developmental and epileptic encephalopathies (DEE) entail moderate to profound impairments in gross motor skills and mobility, which are poorly quantified with clinical outcomes assessments (COA) used in neuro-typical populations. We studied the motor domain of the Adaptive Behavior Assessment System-3 for ages 0-5 years (ABAS) used outside of its intended age range with a focus on raw scores.

METHODS

In a cross-sectional survey, 117 parents of children with a variety of DEEs (ages 1-35 years, median = 9) completed the motor domain section of the ABAS. Floor and ceiling effects and associations with epilepsy-related factors were assessed with appropriate parametric and nonparametric statistical techniques. The sensitivity of the ABAS and additional measures of mobility borrowed from the cerebral palsy literature (Functional Activities Questionnaire (FAQ-22) walking level (FAQ-WL)) to different levels of the Functional Mobility Scale was determined.

RESULTS

ABAS motor scores corresponded to a median age equivalent of 20.5 months (Inter-Quartile Range (IQR) 8-34). Most raw scores corresponded to standardized scores > 2 standard deviations below the ABAS standardization sample mean. ABAS raw scores demonstrated minimal floor and ceiling effects (<5%). In linear regression models, scores increased with age under 6 years (p < 0.0001) but flattened out thereafter. Scores varied substantially by DEE group (p < 0.001) and decreased with higher convulsive seizure frequency (<0.0001) and number of seizure medications (p < 0.001). ABAS and other motor scores were sensitive to important differences in mobility as represented by the FMS at 5 yards. Further, they correlated with declines in mobility function from 5 to 500 yards.

SIGNIFICANCE

An out-of-range COA with raw scores may provide a measure of motor ability and mobility sensitive within the range of moderate to profound impairment seen in patients with DEE. This approach could shorten the time to appropriate COA development and ensure timely clinical trial readiness for novel therapies for rare DEEs.