title: Cutaneous and Mixed Nerve Silent Period Recordings in Symptomatic Paroxysmal Kinesigenic Dyskinesia.
abstract: OBJECTIVE
  The underlying neurophysiologic mechanism responsible for secondary paroxysmal kinesigenic dyskinesia (PKD) is still unclear. Here, we study the pathogenesis of PKD in two patients with a demyelinating lesion in the spinal cord.
  
  
  METHODS
  Electromyogram recordings from affected arms of two patients with spinal cord lesions presenting PKD were compared with our laboratory standards. The cutaneous silent period (CuSP), mixed nerve silent period (MnSP) and coincidence period (CiP), defined as the common period between the CuSP and MnSP, were recorded.
  
  
  RESULTS
  A large decrease in the MnSP and disappearance of the CiP were observed in our patients, which was secondary to simultaneous extinction of the third portion of the MnSP, while the CuSP was normal. The MnSP and CiP were normal after recovery.
  
  
  CONCLUSIONS
  Our results demonstrate that the third portion of the MnSP and the CuSP do not correspond to the same physiologic process. These findings suggest that PKD patients have abnormal spinal interneuron integration.
authors.affiliation: CHU de Caen, Service de Neurologie, CHU de Caen, Caen, F-14000, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Cogez
authors.affiliation: CHU de Caen, Service D'explorations Fonctionnelles du Systeme Nerveux, Caen, F-14000, France; Université de Caen Basse-Normandie, UFR de Médecine, Caen, F-14000, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Etard
authors.affiliation: CHU de Caen, Service de Neurologie, CHU de Caen, Caen, F-14000, France; INSERM, INSERM U923, CHU de Caen, Caen, F-14000, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Derache
authors.affiliation: CHU de Caen, Service de Neurologie, CHU de Caen, Caen, F-14000, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Defer
keywords: Cutaneous silent period; Dystonia; Mixed nerve silent period