Angelman syndrome assessed by neurological and molecular cytogenetic investigations

Anesthesia of a dental patient with Angelman syndrome -A case report-

Angelman syndrome is characterized by a partial deficit of paired autosomal chromosome 15, which contains a subunit of the GABA (Gamma-Amino Butyric Acid) receptor. Many drugs that act on the CNS (Central Nerve System) during anesthesia are believed to exert their effects via the GABA receptors. We describe the anesthesia of a 7 year-old female patient with Angelman syndrome who underwent surgery for dental caries. The basic factors that needed to be considered when administering anesthesia to this patient were epilepsy, significant dominance of the vagal tone, craniofacial abnormalities and peripheral muscular atrophy. Inhalational anesthetics (sevoflurane) were employed for this patient. The patient had an uneventful peri-operative period and was discharged home on the same day of the operation.

Behavior and neuropsychiatric manifestations in Angelman syndrome

Angelman syndrome has been suggested as a disease model of neurogenetic developmental condition with a specific behavioral phenotype. It is due to lack of expression of the UBE3A gene, an imprinted gene located on chromosome 15q. Here we review the main features of this phenotype, characterized by happy demeanor with prominent smiling, poorly specific laughing and general exuberance, associated with hypermotor behavior, stereotypies, and reduced behavioral adaptive skills despite proactive social contact. All these phenotypic characteristics are currently difficult to quantify and have been subject to some differences in interpretation. For example, prevalence of autistic disorder is still debated. Many of these features may occur in other syndromic or nonsyndromic forms of severe intellectual disability, but their combination, with particularly prominent laughter and smiling may be specific of Angelman syndrome. Management of problematic behaviors is primarily based on behavioral approaches, though psychoactive medication (eg, neuroleptics or antidepressants) may be required.

The behavioural phenotype of Angelman syndrome

BACKGROUND

The purpose of this review is to examine the notion of a behavioural phenotype for Angelman syndrome and identify methodological and conceptual influences on the accepted presentation.

METHODS

Studies examining the behavioural characteristics associated with Angelman syndrome are reviewed and methodology is described.

RESULTS

Potential bias in the description of the phenotype emerges with the use of case and cohort studies with the absence of comparison groups. A trend in the literature from a direct gene effect to a socially mediated effect on laughter is evident.

CONCLUSION

Evidence for a behavioural phenotype of Angelman syndrome has begun to emerge. However, by adopting the concept of a 'behavioural phenotype', attention may become biased towards the underlying biological basis of the syndrome, with developmental and environmental factors being overlooked.

Electroclinical characteristics of seizures-comparing Prader--Willi syndrome with Angelman syndrome

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are two clinically distinct neurobehavioral syndromes that are caused by deficiency of gene expression from paternally or maternally derived homologues on chromosome 15q11-q13, respectively. Clinical and genetic heterogeneities are common in both syndromes and they are now regarded as 'sister genetic imprinting syndromes'. This study aimed to describe and compare the electroclinical characteristics of seizures between PWS and AS, and to try to explore the possible mechanisms of epileptogenesis in these two syndromes. Fifty patients with genetically documented PWS and 18 patients with a putative diagnosis of AS were included in this study. These patients were diagnosed on the basis of characteristic physical findings and their neurobehavioral phenotype, as well as cytogenetic and molecular studies. Epileptic seizures were present in 16 of 18 patients with AS, but in only eight of 50 patients with PWS. Using electroencephalography (EEG), the most characteristic findings for AS were rhythmic 2-3 Hz delta waves of high-amplitude that were maximal over the frontal regions, and 3-4 Hz spikes and sharp wave runs posteriorly. These were never seen in PWS. Patients with AS had a much higher incidence of seizures with characteristic EEG findings, similar to those seen in mice that are deficient in a single gene (UBE3A) that displays regional brain-specific imprinting in humans and mice. In this series, cases with no detectable cytogenetic or molecular defect at the AS locus displayed similar AS phenotype, seizure severity and EEG abnormalities compared to those with such a defect. Thus, the UBE3A gene is presumed to be potentially involved in the epileptogenesis of AS. It is also possible that UBE3A and another gene located nearby, gamma-aminobutyric receptorbeta3 subunit, may interact in some way, and result in the severe epilepsy seen with AS. Some patients with PWS and AS share the common EEG features of persistent high-amplitude 4-6 Hz activity in recordings during sleep, and while awake. The significance of such EEG findings needs further experience to clarity.

Thelarche variant in a girl with Angelman syndrome

A case of Angelman syndrome (AS) with thelarche variant in a 4.5-year-old girl is presented. Clinical suspicion of AS was raised at the age of 15 months when she presented with mental retardation and epilepsy, absence of speech, ataxic gait with jerky movements, hyperactivity and paroxysmal episodes of laughter. Moreover, she had facial dysmorphic features such as microbrachycephaly, mid-facial hypoplasia, macrostomia and prominent mandible. Dinucleotide repeat polymorphism (DNRP) analysis, identified absence of maternal alleles at D15S543, D15S113 and GABRB3 loci, findings consistent with AS. Studies on CYP19 locus (outside the 15q11-13 region) revealed the presence of two different alleles, thus excluding the possibility of paternal isodisomy of chromosome 15 in this patient. Breast development at the age of 4.5 years, accompanied by accelerated growth velocity and bone age suggested the diagnosis of variant thelarche. This is the second case of AS with sexual precocity reported and whether this combination is a coincidence or not remains to be clarified.

Distinct multi-joint control strategies in spastic diplegia associated with prematurity or Angelman syndrome

Spastic diplegia is commonly due to periventricular leucomalacia associated with premature birth. It is also a feature of Angelman syndrome (AS), a neurogenetic disorder with developmental delay, absent speech and mirthful behaviour. We studied the kinematics and kinetics of the squatting movement and associated electromyographic (EMG) activities in 20 children with spastic diplegia associated with periventricular leucomalacia (SDPL) or AS and 18 unimpaired children. While movement of normal subjects consisted of vertical translation of most body segments, the movement of SDPL children was operated around the fixed knee with backward shift of the hip, and AS children performed a forward flexion of the trunk over the thigh. Trunk stability was correlated with movement velocity in both pathological groups. In normal subjects, anticipatory EMG pattern consisted of silencing of hamstring muscle tonic activity prior to movement onset. This deactivation was not present in spastic diplegia. In SDPL, anticipatory overactivation of ankle joint actuators was recorded and tonic co-contraction persisted throughout the movement. In AS, rhythmic EMG bursting was seen during the movement. Shoulder, hip and knee trajectories in the sagittal plane showed marked within-group stereotypies in orientation, shape and length. The patterns in both pathological groups were therefore distinctive. We speculate that they reflect corticospinal impairment in SDPL and combined corticospinal and cerebellar dysfunction in AS.

Parental view of epilepsy in Angelman syndrome: a questionnaire study

PURPOSE

To explore parents' opinions and concerns about seizures, anticonvulsants, and the effect of treatment in children with Angelman syndrome.

DESIGN

A postal questionnaire was sent to members of one of the UK lay groups for Angelman syndrome (ASSERT) who had a child affected by Angelman syndrome. The questionnaire requested general medical information and information about the epilepsy, its treatment, and treatment responses.

RESULTS

One hundred and fifty questionnaires were sent out with an ASSERT routine mailing and 78 completed questionnaires were returned. Forty three patients were boys and 35 were girls; ages ranged from 1.7 to 25 years (mean 7.5 years). The overall general clinical and cytogenetic data were mostly consistent with previous reports. Epilepsy was reported in 68 children, most of whom had a detectable cytogenetic deletion. The most common seizure types reported by the families were absence seizures, tonic clonic seizures, drop attacks, and myoclonic seizures; in four patients only febrile seizures occurred. The age at onset of the seizures was < 2 years in more than half of the patients. Anti-epileptic drug treatment with valproate (VPA), clonazepam (CZP), and lamotrigine (LTG) as monotherapy or a combination of VPA and CZP or VPA and LTG was more often viewed favourably and considered effective with fewer side effects on the child's behaviour and alertness, versus more frequent adverse effects and increased frequency and severity of seizures with carbamazepine (CBZ) and vigabatrin (VGB) in monotherapy or in combination with other anti-epileptic drugs. Seizures did tend to improve with age but were still present and disabling at older ages.

CONCLUSIONS

This is the first study to record parents' opinions about seizures, anti-epileptic drugs, and treatment responses in children with Angelman syndrome, and it is one of the largest series on epilepsy and Angelman syndrome to be reported to date.

Angelman syndrome: correlations between epilepsy phenotypes and genotypes

We compared epilepsy phenotypes with genotypes of Angelman syndrome (AS), including chromosome 15q11-13 deletions (class I), uniparental disomy (class II), methylation imprinting abnormalities (class III), and mutation in the UBE3A gene (class IV). Twenty patients were prospectively selected based on clinical cytogenetic and molecular diagnosis of AS. All patients had 6 to 72 hours of closed-circuit television videotaping and digitized electroencephalogrpahic (EEG) telemetry. Patients from all genotypic classes had characteristic EEGs with diffuse bifrontally dominant high-amplitude 1- to 3-Hz notched or triphasic or polyphasic slow waves, or slow and sharp waves. Class I patients had severe intractable epilepsy, most frequently with atypical absences and myoclonias and less frequently with generalized extensor tonic seizures or flexor spasms. Epileptic spasms were recorded in AS patients as old as 41 years. Aged-matched class II, III, and IV patients had either no epilepsy or drug-responsive mild epilepsy with relatively infrequent atypical absences, myoclonias, or atonic seizures. In conclusion, maternally inherited chromosome 15q11-13 deletions produce severe epilepsy. Loss-of-function UBE3A mutations, uniparental disomy, or methylation imprint abnormalities in AS are associated with relatively mild epilepsy. Involvement of other genes in the chromosome 15q11-13 deletion, such as GABRB3, may explain severe epilepsy in AS.