Edoardo Ferlazzo1, Silvana Franceschetti2, Sara Gasparini1, Maurizio Elia3, Laura Canafoglia4, Chiara Pantaleoni5, Michele Ascoli6, Tiziana D'Agostino6, Chiara Sueri6, Giulia Ferrigno6, Ferruccio Panzica4, Vittoria Cianci1, Umberto Aguglia1. 1. Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy; Regional Epilepsy Centre, Great Metropolitan Hospital "Bianchi-Melacrino-Morelli", Reggio Calabria, Italy. 2. Department of Neurophysiopathology, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy. Electronic address: silvana.franceschetti@istituto-besta.it. 3. Oasi Research Institute, IRCCS, Troina, Italy. 4. Department of Neurophysiopathology, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy. 5. Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy. 6. Regional Epilepsy Centre, Great Metropolitan Hospital "Bianchi-Melacrino-Morelli", Reggio Calabria, Italy.
Abstract
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.
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.