Perampanel for nonepileptic myoclonus in Angelman syndrome

Differentiating rhythmic high-amplitude delta with superimposed (poly) spikes from extreme delta brushes: limitations of standardized nomenclature and implications for patient management

BACKGROUND

Following the standardized nomenclature proposed by the American Clinical Neurophysiology Society (ACNS), rhythmic high-amplitude delta activity with superimposed spikes (RHADS) can be reported as an extreme delta brush (EDB). The clinical implications of similar electrographic patterns being reported as RHADS versus EDB are important to highlight. We aim to review the electrographic characteristics of RHADS, evaluate whether RHADS is seen in other neurological disorders, and identify the similar and unique characteristics between RHADS and EDB to ultimately determine the most accurate way to differentiate and report these patterns. We believe that the differentiation of RHADS and EDB is important as there is a vast difference in the diagnostic approach and the medical management of associated underlying etiologies.

DATA SOURCE

We conducted an extensive search on MEDLINE and Pubmed utilizing various combinations of keywords. Searching for "gamma polymerase and EEG", or "RHADS" or "Alpers syndrome and EEG" or "EEG" AND "Alpers-Huttenlocher syndrome".

RESULTS

Three articles were found to be focused on the description of "RHADS" pattern in Alpers Syndrome. No publication to date were found when searching for the terms "EDB" AND "children", AND "infant" AND "adolescent" excluding "encephalitis" and "neonate". Although RHADS and EDB appear as similar EEG patterns, meticulous analysis can differentiate them. RHADS is not exclusive to patients with Alpers-Huttenlocher syndrome and may manifest in regions beyond the posterior head region. Reactivity to eye-opening and response to anesthesia can be two other elements that help in the differentiation of these patterns.

CONCLUSION

RHADS is not exclusive to patients with AHS and may manifest in regions beyond the posterior head region. Reactivity to eye-opening and response to anesthesia are features that help in the differentiation of these patterns.

Perampanel for the treatment of epilepsy with genetic aetiology: Real-world evidence from the PERMIT Extension study

Genetic factors contribute to the aetiology of epilepsy in >50% of cases, and information on the use of antiseizure medications in people with specific aetiologies will help guide treatment decisions. The PERMIT Extension study pooled data from two real-world studies (PERMIT and PROVE) to investigate the effectiveness and safety/tolerability of perampanel (PER) when used to treat people with focal and generalised epilepsy in everyday clinical practice. This post-hoc analysis of PERMIT Extension explored the use of PER when used to treat individuals presumed to have epilepsy with a genetic aetiology. Assessments included retention rate (evaluated at 3, 6 and 12 months), effectiveness (responder and seizure freedom rates; evaluated at 3, 6, 12 months and the last visit [last observation carried forward) and tolerability (adverse events [AEs]). Of the 6822 people with epilepsy included in PERMIT Extension, 1012 were presumed to have a genetic aetiology. The most common genetic aetiologies were idiopathic generalised epilepsy (IGE; 58.2%), tuberous sclerosis (1.1%), Dravet syndrome (0.8%) and genetic epilepsy with febrile seizures plus (GEFS+; 0.5%). Retention rates at 3, 6 and 12 months in the total genetic aetiology population were 89.3%, 79.7% and 65.9%, respectively. In the total genetic aetiology population, responder rates at 12 months and the last visit were 74.8% and 68.3%, respectively, and corresponding seizure freedom rates were 48.9% and 46.5%, respectively. For the specific aetiology subgroups, responder rates at 12 months and the last visit were, respectively: 90.4% and 84.4% (IGE), 100% and 57.1% (tuberous sclerosis), 100% and 71.4% (Dravet syndrome), and 33.3% and 20.0% (GEFS+). Corresponding seizure freedom rates were, respectively: 73.1% and 64.6% (IGE), 33.3% and 22.2% (tuberous sclerosis), 20.0% and 28.6% (Dravet syndrome), and 0% and 0% (GEFS+). The incidence of AEs was 46.5% for the total genetic aetiology population, 48.8% for IGE, 27.3% for tuberous sclerosis, 62.5% for Dravet syndrome, and 20% for GEFS+. Tolerability findings were consistent with PER's known safety profile. PER was effective and generally well tolerated when used in individuals with a presumed genetic epilepsy aetiology in clinical practice. PER was effective across a wide range of genetic aetiologies.

Current and emerging treatment options for Angelman syndrome

INTRODUCTION

Angelman syndrome (AS) is a neurodevelopmental disorder characterized by intellectual disability, limited expressive language, epilepsy, and motor impairment. Angelman syndrome is caused by haploinsufficiency of the UBE3A gene on the maternal copy of chromosome 15. There have been ongoing advances in the understanding of neurological, behavioral, and sleep-based problems and associated treatments for patients with AS. These results along with gene-based therapies entering into clinical development prompted this review.

AREAS COVERED

The authors summarize the research basis describing phenomenology of epilepsy and behavioral concerns such as hyperactivity behavior, aggression, self-injury, repetitive behavior, and sleep disorder. The evidence for recent treatment advances in these target symptom domains of concern is reviewed, and the potential for emerging gene therapy treatments is considered.

EXPERT OPINION

The prospect for emerging gene therapies means that increasing efforts should be directed toward the early identification of AS implemented equitably. Recent studies emphasize the important role of behavioral therapy in addressing mental health concerns such as aggression and disordered sleep.

Myoclonus and other jerky movement disorders

Myoclonus and other jerky movements form a large heterogeneous group of disorders. Clinical neurophysiology studies can have an important contribution to support diagnosis but also to gain insight in the pathophysiology of different kind of jerks. This review focuses on myoclonus, tics, startle disorders, restless legs syndrome, and periodic leg movements during sleep. Myoclonus is defined as brief, shock-like movements, and subtypes can be classified based the anatomical origin. Both the clinical phenotype and the neurophysiological tests support this classification: cortical, cortical-subcortical, subcortical/non-segmental, segmental, peripheral, and functional jerks. The most important techniques used are polymyography and the combination of electromyography-electroencephalography focused on jerk-locked back-averaging, cortico-muscular coherence, and the Bereitschaftspotential. Clinically, the differential diagnosis of myoclonus includes tics, and this diagnosis is mainly based on the history with premonitory urges and the ability to suppress the tic. Electrophysiological tests are mainly applied in a research setting and include the Bereitschaftspotential, local field potentials, transcranial magnetic stimulation, and pre-pulse inhibition. Jerks due to a startling stimulus form the group of startle syndromes. This group includes disorders with an exaggerated startle reflex, such as hyperekplexia and stiff person syndrome, but also neuropsychiatric and stimulus-induced disorders. For these disorders polymyography combined with a startling stimulus can be useful to determine the pattern of muscle activation and thus the diagnosis. Assessment of symptoms in restless legs syndrome and periodic leg movements during sleep can be performed with different validated scoring criteria with the help of electromyography.

Therapeutic approach to neurological manifestations of Angelman syndrome

INTRODUCTION

Angelman syndrome (AS) is a neurogenetic disorder due to deficient expression of the maternal copy of the UBE3A gene, which encodes ubiquitin ligase E3A protein. Severe developmental delay, seizures and other neurological disorders characterizes AS.

AREAS COVERED

In this review, we focus on a comprehensive therapeutic approach to the most disabling neurological manifestations of AS: epilepsy, sleep disturbances, behavioral and movement disorders. Articles were identified through PubMed and Google Scholar up to October 2021.

EXPERT OPINION

Evidence for the treatment of neurological manifestations in AS mainly derives from poor quality studies (case reports, small case series, expert opinions). Seizures can be polymorphic and includes atypical absences, myoclonic, generalized tonic-clonic, unilateral clonic, or atonic attacks. Sodium valproate, levetiracetam and benzodiazepines are the most commonly used anti-seizure medications. Melatonin or mirtazapine seem to improve sleep quality. Antipsychotics, antidepressants and anxiolytics have been proposed for treatment of behavioral manifestations, but no evidence-based studies are available. Non-pharmacological approach may also be useful. Mild dystonia is common but usually does not significantly impact patients' motor performances. Well-conducted clinical trials aimed to evaluate treatment of neurological complications of AS are warranted. Gene and molecular precision therapies represent a fascinating area of research in the future.

Pharmacotherapeutic management of seizures in patients with Angleman syndrome

Approximately 80-90% of patients with Angelman syndrome (AS) develop childhood-onset intractable seizures with major negative impact on the quality of life.Thus adequate management of seizures is the most critical priority to improve health-related quality of life in children with AS.

AREAS COVERED

The primary focus of the review is on pharmacotherapeutic management of seizures. The first part of the review briefly discusses epileptogenesis and polymorphic seizure phenotypes associated with AS to understand pharmacotherapeutic decision-making better. Next, the review explores individual antiseizure medicines (ASMs) and their potential therapeutic utility. Lastly, some future and emerging treatment options are discussed that can transform the management of seizures in patients with AS.

EXPERT OPINION

Evidence for treating seizures in AS mainly derives from low-quality studies. Levetiracetam and clobazam are the most commonly used ASMs. Although the potential utility of several other ASMs(valproate, topiramate, lamotrigine, ethosuximide, clonazepam) has been well documented for some time, the treatment landscape may rapidly evolve due to the availability of newer and better tolerated ASMs(cannabidiol oil, brivaracetam, perampanel). In addition, a better understanding of the underlying pathogenesis and the development of molecular therapeutics offer hope for precision therapies for seizures.

A multidisciplinary approach and consensus statement to establish standards of care for Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a rare neurogenetic disorder present in approximately 1/12,000 individuals and characterized by developmental delay, cognitive impairment, motor dysfunction, seizures, gastrointestinal concerns, and abnormal electroencephalographic background. AS is caused by absent expression of the paternally imprinted gene UBE3A in the central nervous system. Disparities in the management of AS are a major problem in preparing for precision therapies and occur even in patients with access to experts and recognized clinics. AS patients receive care based on collective provider experience due to limited evidence-based literature. We present a consensus statement and comprehensive literature review that proposes a standard of care practices for the management of AS at a critical time when therapeutics to alter the natural history of the disease are on the horizon.

METHODS

We compiled the key recognized clinical features of AS based on consensus from a team of specialists managing patients with AS. Working groups were established to address each focus area with committees comprised of providers who manage >5 individuals. Committees developed management guidelines for their area of expertise. These were compiled into a final document to provide a framework for standardizing management. Evidence from the medical literature was also comprehensively reviewed.

RESULTS

Areas covered by working groups in the consensus document include genetics, developmental medicine, psychology, general health concerns, neurology (including movement disorders), sleep, psychiatry, orthopedics, ophthalmology, communication, early intervention and therapies, and caregiver health. Working groups created frameworks, including flowcharts and tables, to help with quick access for providers. Data from the literature were incorporated to ensure providers had review of experiential versus evidence-based care guidelines.

CONCLUSION

Standards of care in the management of AS are keys to ensure optimal care at a critical time when new disease-modifying therapies are emerging. This document is a framework for providers of all familiarity levels.

Flurothyl-induced seizure paradigm revealed higher seizure susceptibility in middle-aged Angelman syndrome mouse model

INTRODUCTION

Epilepsy is one of the main clinical problems in Angelman syndrome (AS). Seizures typically start in early childhood then decrease or are often alleviated by young adulthood. Several studies using AS model mice showed comparable seizure susceptibility during young adulthood. In contrast, the course of epilepsy post young adulthood differs from persistently relieved to rerising among reports. To elucidate this, we evaluated the seizure susceptibility of AS model mice of two different ages.

METHODS

Mice lacking maternal Ube3a gene (Ube3a^m-/p+) of C57BL/6 background or their littermate wild type (WT) were divided into two groups by age, 2 to 3 months (2-3 M) and 6 to 12 months (6-12 M), corresponding to adolescent to young adult aged and middle aged humans, respectively. Seizure susceptibility was evaluated by flurothyl inhalation or intraperitoneal injection of pentylenetetrazole (PTZ IP)-induced acute seizure protocol.

RESULTS

In the flurothyl-induced seizure paradigm, the latency to seizure occurrence had a significant interaction with genotype and age. Post-hoc analysis revealed that the latency was significantly shorter at 6-12 M than at 2-3 M in Ube3a^m-/p+ mice, and in Ube3a^m-/p+ mice than in WT mice at 6-12 M. No significant interaction or difference was observed by PTZ IP.

CONCLUSION

The flurothyl-induced seizure paradigm revealed that seizure susceptibility of Ube3a^m-/p+ mice increased with age, similar to clinical studies reporting the reappearance of epilepsy in older age. The flurothyl-induced seizure paradigm applied to middle-aged Ube3a^m-/p+ mice could be a suitable protocol for screening drugs against seizures in AS.

Epilepsy in Angelman syndrome: A scoping review

Angelman Syndrome (AS) is characterized by severe developmental delays including marked speech impairment, movement abnormalities(ataxia, tremor), and unique behaviors such as frequent laughter and is caused by dysfunctional maternal UBE3A gene (maternal 15q11-13 deletions, maternal specific UBE3A mutation, uniparental disomy, and imprinting defect). Intractable epileptic seizures since early childhood with characteristic EEG abnormalities are present in 80-90% patients with AS. Underlying pathophysiology may involve neocortical and thalamocortical hyperexcitability secondary to severe reduction of GABAergic input, as well as dysfunctional synaptic plasticity, deficient synaptogenesis, and neuronal morphological immaturity. The onset of epilepsy is most prevalent between 1 and 3 years of age; however, approximately 25% of patients developed epilepsy before one year of age. Various types of generalized seizures are most prevalent, with most common types are myoclonic and atypical absence.More than 95% of epilepsy patients may have daily seizures at least for a limited time during early childhood, and two-third patients develop disabling seizures. Fever provoked seizures, and frequent occurrence of nonconvulsive status epilepticus are two unique features. Seizures are frequently pharmacoresistant. Considering underlying prominent GABAergic dysfunction, clinicians had used AEDs that target GABAergic signaling such as valproate, phenobarbital, and clonazepam as first-line therapies for AS. However, due to the unfavorable side effect profile of these AEDs, a recent treatment approach involves priority use of levetiracetam, clobazam, topiramate, lamotrigine, ethosuximide, VNS, and carbohydrate-restricted diets. Besides symptomatic management, there has been recent progress to find a curative treatment with the following approaches: 1. Gene/protein replacement therapy (Adeno and lentiviral vector therapy to deliver a gene or secretory protein); 2. Activation of the intact but silent paternal copy of UBE3A (antisense oligonucleotide therapy and artificial transcription factors); and 3. Downstream therapies (OV101/gaboxadol, ketone supplement, novel compounds/peptides, anti-inflammatory/regenerative therapy).