Abstracts

Rationale: Movement disorders are a common finding in Angelman syndrome (AS), even though there are few reports in literature (Guerrini R, et al. Cortical myoclonus in Angelman syndrome. Ann Neurol 1996;40:39-48; Goto M, et al. Episodic tremors representing cortical myoclonus are characteristic in Angelman syndrome due to UBE3A mutations. Brain Develop 2015;37:216–222). Cortical myoclonus with or without electroencephalographic changes has been commonly described, but in small series only. Despite they represent a hallmark of the disease, abnormal movements in AS are still poorly characterized. The existence of dystonic limb posturing in subjects with AS has been reported in a single study, but its characteristics and prevalence are still unknown. The aim of our study is to evaluate the prevalence and the severity of myoclonus and dystonia in a wide cohort of subjects with AS. Methods: Patients with AS were included during AS Organisation (OrSA) Italian conferences; clinical history, neuropsychological evaluation, video-EEG and simultaneous surface EMG with myoclonus activation tasks were performed. We tested: severity, electrophysiological characteristics and neurological examination during myoclonus activating tasks; moreover presence, localization and severity of dystonia were assessed.  Results: We studied 61 subjects with genetically confirmed AS. Twenty-four patients were sufficiently cooperative with EEG/EMG and were included in the present study (12 female, median age 19 years, range 3-48). Rest myoclonus was evident in 16/24 (66.7%) subjects and, in all of them, it was not associated to changes of EEG activity. Eighteen patients (15/18 treated with antiepileptic drugs) presented with action cortical myoclonus localized at upper limbs, without EEG alterations, increased by activating tasks. Other activating maneuvers did not enhance myoclonus in any subject. A polygraphic pattern of postural tremor (alternating contraction of agonist and antagonist muscles) was recorded in one patient who also had rest myoclonus. Myoclonus was severe (> 1 minute) in 13/18 patients. According to a global clinical impression scale, disability deriving from myoclonus was mild (8/24 patients, 33.3%) or moderate (10/24 patients, 41.7%). Twenty-one of 24 patients presented with upper limbs dystonia of different severity (moderate in 12/21, mild in 9/21) and 5/21 with neck dystonia (moderate in 4/5, mild in 1/5).  Conclusions: Our study involves a large sample of patients with AS. Our findings demonstrate that cortical myoclonus is common and not associated with EEG alterations. Although myoclonus may be frequent and severe, its impact on perceived disability is not weighty. Dystonia is also severe and more commonly involves upper limbs. Funding: None