title: Characterization of severe action myoclonus in sialidoses.
abstract: To asses the characteristics of severe action myoclonus in three patients with progressive myoclonus epilepsy (PME) due to sialidosis. We assessed EEG-EMG coherence, relative power (RP) and bandwidth (BW) of the EMG-peak associated with myoclonus; we also evaluated somatosensory evoked potentials and long-loop reflexes (LLRs). We compared the findings with those obtained in ten Unverricht-Lundborg (UL) patients. The presentation of sialidosis included macular cherry-red spot, skeletal malformation and polyneuropathy in the infantile form and optic atrophy in the juvenile form. From its onset in adolescence myoclonus rapidly worsened, quickly leading to severe disability. In sialidosis patients, the EMG-peak was characterised by higher RP (p<0.01) and narrower BW (p<0.02) than in UL. EEG-EMG coherence values were higher (p<0.05) than in UL patients. Taking into account both sialidosis and UL patients, the coherence values and the RP of the EMG-peak were directly correlated with the severity of the myoclonus; while BW values were inversely correlated. All these measures showed extreme values in sialidosis patients. In the sialidosis patients, the strongly rhythmic recurrence of the jerks reflected on LLR, which included multiple components. Subtle differences indicate an especially high level of cortical motor synchronization in the sialidosis patients, which may account for their particularly severe motor impairment. Neurophysiological indexes indicating high EEG-EMG synchronization parallels the severity of the myoclonus.
authors.affiliation: Dept of Neurophysiopathology, IRCCS Foundation Carlo Besta Neurological Institute, Milano, Italy. canafoglia@istituto-besta.it
authors.forename: Laura
authors.initials: L
authors.lastname: Canafoglia
authors.forename: Silvana
authors.initials: S
authors.lastname: Franceschetti
authors.forename: Graziella
authors.initials: G
authors.lastname: Uziel
authors.forename: Claudia
authors.initials: C
authors.lastname: Ciano
authors.forename: Vidmer
authors.initials: V
authors.lastname: Scaioli
authors.forename: Renzo
authors.initials: R
authors.lastname: Guerrini
authors.forename: Elisa
authors.initials: E
authors.lastname: Visani
authors.forename: Ferruccio
authors.initials: F
authors.lastname: Panzica
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology; D004569:Electroencephalography / Q000379:methods; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009081:Mucolipidoses / Q000150:complications*; D009207:Myoclonus / Q000175:diagnosis* / Q000209:etiology*; D013057:Spectrum Analysis; D055815:Young Adult