title: Cortical myoclonus in childhood and juvenile onset Huntington's disease.
abstract: OBJECTIVE
  Huntington's disease (HD) appearing before the age of 20 years gives rise to a distinct phenotype with respect to the classical adult-onset disease. Here we describe three patients with childhood or juvenile HD onset presenting with action myoclonus.
  
  
  METHODS
  We performed jerk-locked back-averaging (JLBA), EEG-EMG coherence and phase analysis, long-loop reflexes (LLRs) and somatosensory evoked potentials (SSEPs). In one patient, we also performed transcranial magnetic stimulation (TMS) using single and paired pulses.
  
  
  RESULTS
  In all patients, the EMG features revealed movement activated quasi-rhythmic repetitive jerks; the JLBA and EEG-EMG spectral and coherence profiles indicated a cortical generator of the myoclonus. All patients had enhanced LLRs during muscle contraction, while none showed giant SSEPs. The evaluation of intracortical inhibition by means of TMS revealed reduced inhibition at short and long interstimulus intervals.
  
  
  CONCLUSIONS
  The rhythmic course of the action myoclonus and the characteristics of the LLRs suggest that myoclonus is due to a reverberant circuit involving the motor cortex, possibly because of an imbalance between excitatory and inhibitory cortical neuronal systems.
  
  
  CONCLUSIONS
  Our findings suggest a similar cortical dysfunction in childhood and juvenile onset HD, which probably results from a specific circuitry impairment.
authors.affiliation: Dept. of Neurophysiopathology and Epilepsy Centre, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Rossi Sebastiano
authors.forename: Paola
authors.initials: P
authors.lastname: Soliveri
authors.forename: Ferruccio
authors.initials: F
authors.lastname: Panzica
authors.forename: Isabella
authors.initials: I
authors.lastname: Moroni
authors.forename: Cinzia
authors.initials: C
authors.lastname: Gellera
authors.forename: Isabella
authors.initials: I
authors.lastname: Gilioli
authors.forename: Nardo
authors.initials: N
authors.lastname: Nardocci
authors.forename: Claudia
authors.initials: C
authors.lastname: Ciano
authors.forename: Alberto
authors.initials: A
authors.lastname: Albanese
authors.forename: Silvana
authors.initials: S
authors.lastname: Franceschetti
authors.forename: Laura
authors.initials: L
authors.lastname: Canafoglia
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography; D004576:Electromyography; D005073:Evoked Potentials, Somatosensory; D006801:Humans; D006816:Huntington Disease / Q000150:complications / Q000503:physiopathology*; D009207:Myoclonus / Q000150:complications / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation