Reserpine responsive myoclonus and hyperpyrexia in a patient with Angelman syndrome

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.

Connectivity measures suggest a sub-cortical generator of myoclonus in Angelman syndrome

OBJECTIVE

The clinical and neurophysiological characteristics of myoclonus in Angelman syndrome (AS) have been evaluated in single case or small cohorts, with contrasting results. We evaluated the features of myoclonus in a wide cohort of AS patients.

METHODS

We performed polygraphic EEG-EMG recording in 24 patients with genetically confirmed AS and myoclonus. Neurophysiological investigations included jerk-locked back-averaging (JLBA), cortico-muscular coherence (CMC) and generalised partial directed coherence (GPDC). CMC and GPDC analyses were compared to those obtained from 10 healthy controls (HC).

RESULTS

Twenty-four patients (aged 3-35 years, median 20) were evaluated. Sequences of quasi-continuous rhythmic jerks mostly occurred at alpha frequency or just below (mean 8.4 ± 1.4 Hz), without EEG correlate. JLBA did not show any clear transient preceding the jerks. CMC showed bilateral over-threshold CMC in alpha band that was prominent on the contralateral hemisphere in the patient group as compared to HC group. GPDC showed a significantly higher alpha outflow from both hemispheres toward activated muscles in the patient group, and a significantly higher beta outflow from contralateral hemisphere in the HC group.

CONCLUSIONS

These neurophysiological findings suggest a subcortical generator of myoclonus in AS.

SIGNIFICANCE

Myoclonus in AS has not a cortical origin as previously hypothesised.

Myoclonus in Angelman syndrome

Angelman syndrome (AS) is a neurogenetic imprinting disorder caused by loss of the maternally inherited Ube3a gene and is characterized by generalized epilepsy, limited expressive speech, sleep dysfunction, and movement disorders. Myoclonic seizures are often the first seizure type to appear, and myoclonic status, associated with developmental regression, may occur in the first few years of life. Additionally, there have been rare reports of prolonged episodes of myoclonus without electrographic correlate in adults with AS. The medical records of 200 individuals seen in the Angelman Syndrome Clinic at the Massachusetts General Hospital and the Lurie Center for Autism were retrospectively reviewed to identify and characterize myoclonic seizures and episodes of nonepileptic myoclonus. Myoclonic seizures were reported in 14% of individuals with age of onset occurring before 8years. These are brief events, unless the individual was experiencing myoclonic status, and electroencephalographs show interictal generalized spike and wave activity. Nonepileptic myoclonus occurred in 40% of individuals over 10years of age, and prevalence appears to increase with age. The episodes of nonepileptic myoclonus arise during puberty or later, with age of onset ranging from 10 to 26years. These events were captured on 5 video electroencephalographs and had no electrographic correlate. They can last from seconds to hours, always occurring in the hands and spreading to the face and all extremities in some individuals. Episodes of nonepileptic myoclonus have a discrete beginning and end, lacks a postictal period, and are not associated with significant alteration of consciousness or developmental regression. These episodes can be difficult to treat and are often refractory to medication; however, levetiracetam, clobazam, and clonazepam appear to be effective for some individuals. Myoclonic seizures are common in AS, typically occurring in young children and associated with epileptiform changes on electroencephalographs. Prolonged episodes are associated with developmental regression. In contrast, nonepileptic myoclonus typically begins in adolescence or early adulthood and has no electroencephalogram (EEG) correlate, alteration in consciousness, or regression but can significantly impact quality of life.

Myoclonic status and central fever in Angelman syndrome due to paternal uniparental disomy

Myoclonic status in nonprogressive encephalopathy (MSNE) is an early-onset, drug-resistant epileptic syndrome characterized by occurrence of continuous diffuse epileptiform abnormalities, associated with positive and/or negative phenomena and accompanied by transient and recurring motor, cognitive, and behavioral impairment. MSNE has been reported in Angelman syndrome (AS) secondary to 15q11-13 deletions or UBE3A mutations but not to paternal uniparental disomy (UPD). We describe the case of a male patient with AS caused by UPD who developed a myoclonic status (MS) associated with long-lasting fever of central origin, both promptly regressed with introduction of levetiracetam. Only three descriptions of thermal dysregulation in AS exist, and none of the previously reported cases were associated with MS or with UPD. Association of MS and central fever expands the spectrum of epileptic and non-epileptic features in UPD-related AS and provides a further evidence of hypothalamus involvement in the pathogenesis of this neurodevelopmental disorder.

Angelman syndrome in adulthood

Angelman syndrome (AS) is a neurogenetic disorder. The goal of this study was to investigate the primary health issues affecting adults with AS and to further characterize the natural history and genotype-phenotype correlations. Standardized phone interviews with caregivers for 110 adolescents and adults with AS were conducted. The impact of age, sex, and genotype on specific outcomes in neurology, orthopedics, internal medicine, and psychiatry were investigated. The mean age of individuals with AS was 24 years (range 16-50y). Active seizures were present in 41% of individuals, and 72% had sleep dysfunction. Significant constipation was present in 85%, and 32% were overweight or obese, with obesity disproportionately affecting women. Scoliosis affected 50% with a mean age at diagnosis of 12 years, and 24% of those diagnosed with scoliosis required surgery, an intervention disproportionately affecting men. Sixty-eight percent were able to walk independently, and 13% were able to speak 5 or more words. Self-injurious behavior was exhibited in 52% of individuals. The results of this study indicate that epilepsy severity may assume a bimodal age distribution: seizures are typically most severe in early childhood but may recur in adulthood. While late-adolescent and adult sleep patterns were improved when compared to the degree of sleep dysfunction present during infancy and childhood, the prevalence of poor sleep in adults remained quite high. Primary areas of clinical management identified include the following: seizures, sleep, aspiration risk, GERD, constipation, dental care, vision, obesity, scoliosis, bone density, mobility, communication, behavior, and anxiety.

Altered serotonin, dopamine and norepinepherine levels in 15q duplication and Angelman syndrome mouse models

Childhood neurodevelopmental disorders like Angelman syndrome and autism may be the result of underlying defects in neuronal plasticity and ongoing problems with synaptic signaling. Some of these defects may be due to abnormal monoamine levels in different regions of the brain. Ube3a, a gene that causes Angelman syndrome (AS) when maternally deleted and is associated with autism when maternally duplicated has recently been shown to regulate monoamine synthesis in the Drosophila brain. Therefore, we examined monoamine levels in striatum, ventral midbrain, frontal cerebral cortex, cerebellar cortex and hippocampus in Ube3a deficient and Ube3a duplication animals. We found that serotonin (5HT), a monoamine affected in autism, was elevated in the striatum and cortex of AS mice. Dopamine levels were almost uniformly elevated compared to control littermates in the striatum, midbrain and frontal cortex regardless of genotype in Ube3a deficient and Ube3a duplication animals. In the duplication 15q autism mouse model, paternal but not maternal duplication animals showed a decrease in 5HT levels when compared to their wild type littermates, in accordance with previously published data. However, maternal duplication animals show no significant changes in 5HT levels throughout the brain. These abnormal monoamine levels could be responsible for many of the behavioral abnormalities observed in both AS and autism, but further investigation is required to determine if any of these changes are purely dependent on Ube3a levels in the brain.

Understanding the pathogenesis of Angelman syndrome through animal models

Angelman syndrome (AS) is a neurodevelopmental disorder characterized by severe mental retardation, lack of speech, ataxia, susceptibility to seizures, and unique behavioral features such as easily provoked smiling and laughter and autistic features. The disease is primarily caused by deletion or loss-of-function mutations of the maternally inherited UBE3A gene located within chromosome 15q11-q13. The UBE3A gene encodes a 100 kDa protein that functions as ubiquitin ligase and transcriptional coactivator. Emerging evidence now indicates that UBE3A plays a very important role in synaptic function and in regulation of activity-dependent synaptic plasticity. A number of animal models for AS have been generated to understand the disease pathogenesis. The most widely used model is the UBE3A-maternal-deficient mouse that recapitulates most of the essential features of AS including cognitive and motor abnormalities. This paper mainly discusses various animal models of AS and how these models provide fundamental insight into understanding the disease biology for potential therapeutic intervention.

Clinical and genetic aspects of Angelman syndrome

Angelman syndrome is characterized by severe developmental delay, speech impairment, gait ataxia and/or tremulousness of the limbs, and a unique behavioral phenotype that includes happy demeanor and excessive laughter. Microcephaly and seizures are common. Developmental delays are first noted at 3 to 6 months age, but the unique clinical features of the syndrome do not become manifest until after age 1 year. Management includes treatment of gastrointestinal symptoms, use of antiepileptic drugs for seizures, and provision of physical, occupational, and speech therapy with an emphasis on nonverbal methods of communication. The diagnosis rests on a combination of clinical criteria and molecular and/or cytogenetic testing. Analysis of parent-specific DNA methylation imprints in the 15q11.2-q13 chromosome region detects approximately 78% of individuals with lack of maternal contribution. Less than 1% of individuals have a visible chromosome rearrangement. UBE3A sequence analysis detects mutations in an additional 11% of individuals. The remaining 10% of individuals with classic phenotypic features of Angelman syndrome have a presently unidentified genetic mechanism and thus are not amenable to diagnostic testing. The risk to sibs of a proband depends on the genetic mechanism of the loss of the maternally contributed Angelman syndrome/Prader-Willi syndrome region: typically <1% for probands with a deletion or uniparental disomy; as high as 50% for probands with an imprinting defect or a mutation of UBE3A. Members of the mother's extended family are also at increased risk when an imprinting defect or a UBE3A mutation is present. Chromosome rearrangements may be inherited or de novo. Prenatal testing is possible for certain genetic mechanisms.

Angelman syndrome: current understanding and research prospects

Angelman syndrome is a neurogenetic disorder characterized by developmental delay, severe intellectual disability, absent speech, exuberant behavior with happy demeanor, motor impairment, and epilepsy, due to deficient UBE3A gene expression that may be caused by various abnormalities of chromosome 15. Recent findings in animal models demonstrated altered dendritic spine formation as well as both synaptic [including gamma-aminobutyric acid (GABA)(A) and N-methyl-D-aspartate (NMDA) transmission] and nonsynaptic (including gap junction) influences in various brain regions, including hippocampus and cerebellar cortex. Reversal of selected abnormalities in rescue genetically engineered animal models is encouraging, although it should not be misinterpreted as promising "cure" for affected patients. Much research is still required to fully understand the functional links between lack of UBE3A expression and clinical manifestations of Angelman syndrome. Studies of regulation of UBE3A expression, including imprinting-related methylation, may point to possibilities of therapeutic upregulation. Understanding relevant roles of the gene product might lead to targeted intervention. Further documentation of brain network dynamics, with particular emphasis on hippocampus, thalamocortical, and cerebellar networks is needed, including in a developmental perspective. There is also a need for further clinical research for improving management of problems such as epilepsy, behavior, communication, learning, motor impairment, and sleep disturbances.

Treatment options for epileptic myoclonus and epilepsy syndromes associated with myoclonus

BACKGROUND

Myoclonus is a brief shock-like movement that has many different etiologies. The degree to which it disturbs quality of life is extremely variable, as is its response to treatment.

OBJECTIVE

In this review, we focus on the treatment strategies for epileptic myoclonus in some common disorders, and in others that are not so common but where myoclonus is a prominent feature and has been studied more.

METHODS

An extended literature review in the English language was conducted through PubMed and text books.

CONCLUSION

Epileptic myoclonus is a manifestation of cortical irritability. The precise etiology is important when determining the best course of treatment. Response to treatment is variable and usually depends on the epileptic syndrome. Some antiepileptic drugs may worsen myoclonus even in patients with syndromes where most patients have a good response to that same drug. Therefore, clinicians must always have in mind that worsening in myoclonus may be ameliorated by decrease or withdrawal rather than increase of medication.

Benefit of corticosteroid therapy in Angelman syndrome

Angelman syndrome is often associated with an intractable seizure disorder. We describe 4 children who demonstrated an excellent response to corticosteroid therapy. The benefits included not only reduction in clinical seizures but also modification of the "typical'' Angelman electroencephalogram. In addition, there was improvement in the myoclonic jerks, sleep pattern, and developmental progress. Corticosteroids appeared to have a broad benefit on the epileptic encephalopathy. We believe that these cases pose a challenge to the conventional management of intractable epilepsy in Angelman syndrome.

Long-standing fever and Angelman syndrome: report of two cases

An 8-month-old girl and a 20-month-old boy who presented with motor and developmental delay and long-standing fever are presented. The patients were diagnosed as Angelman syndrome with fluorescence in situ hybridization (FISH) analysis. Despite extensive clinical and laboratory examinations, no inflammatory or infectious origin for the fever was found. It was considered that the long-standing fever observed in these cases was due to hypothalamic dysfunction for thermoregulation.

Epilepsy in Angelman syndrome

Angelman syndrome is a neurogenetic disorder caused by lack of UBE3A gene expression from the maternally inherited chromosome 15 due to various 15q11-q13 abnormalities. In addition to severe developmental delay, virtual absence of speech, motor impairment, a behavioural phenotype that includes happy demeanor, and distinctive rhythmic electroencephalographic features, over 90% of patients have epilepsy. Many different seizure types may occur, atypical absences and myoclonic seizures being particularly prevalent. Non-convulsive status epilepticus is common, sometimes in the context of the epileptic syndrome referred to as myoclonic status in non-progressive encephalopathies. Epilepsy predominates in childhood, but may persist or reappear in adulthood. Management is difficult in a proportion of patients. It might be improved by better understanding of pathophysiology. Current hypotheses involve abnormal inhibitory transmission due to impaired regulation of GABAA receptors related to functional absence of UBE3A and abnormal hippocampal CaMKII activity.

Angelman syndrome 2005: updated consensus for diagnostic criteria

In 1995, a consensus statement was published for the purpose of summarizing the salient clinical features of Angelman syndrome (AS) to assist the clinician in making a timely and accurate diagnosis. Considering the scientific advances made in the last 10 years, it is necessary now to review the validity of the original consensus criteria. As in the original consensus project, the methodology used for this review was to convene a group of scientists and clinicians, with experience in AS, to develop a concise consensus statement, supported by scientific publications where appropriate. It is hoped that this revised consensus document will facilitate further clinical study of individuals with proven AS, and assist in the evaluation of those who appear to have clinical features of AS but have normal laboratory diagnostic testing.