title: The neurophysiological features of myoclonus-dystonia and differentiation from other dystonias.
abstract: OBJECTIVE
  Myoclonus-dystonia (M-D) is a clinical syndrome characterized by a combination of myoclonic jerks and mild to moderate dystonia. The syndrome is related to ε-sarcoglycan (SGCE) gene mutations in about half the typical cases. Whether the M-D phenotype reflects a primary dysfunction of the cerebellothalamocortical pathway or of the striatopallidothalamocortical pathway is unclear. The exact role of an additional cortical dysfunction in the pathogenesis of M-D is also unknown.
  
  
  OBJECTIVE
  To clarify the neurophysiological features of M-D and discuss whether M-D due to SGCE deficiency differs from other primary dystonias.
  
  
  METHODS
  We studied a referred sample of 12 patients with M-D (mean [SD] age, 28.8 [6.2] years; age range, 19-38 years; 5 women) belonging to 11 unrelated families with a proven mutation or deletion of the SGCE gene and a group of 12 age- and sex-matched healthy control individuals. Every participant underwent 3 sessions exploring the excitability of the primary motor cortex, the response of the primary motor cortex to a plasticity-inducing protocol, and the cerebellar-dependent eye-blink classic conditioning (EBCC). The clinical evaluation of patients included the Unified Myoclonus Rating Scale and Burke-Fahn-Marsden Dystonia Rating Scale.
  
  
  METHODS
  Myoclonus-dystonia with a proven SGCE mutation.
  
  
  METHODS
  We measured resting and active motor thresholds, and short-interval intracortical inhibition and facilitation. The plasticity of the motor cortex was evaluated before and for 30 minutes after 600 pulses of rapid paired associative stimulation. The cerebellar functioning was evaluated with the number of conditioned responses during the 6 blocks of EBCC and 1 extinction block. All data were compared between the 2 groups. For patients, correlations were explored between electrophysiological data and clinical scores.
  
  
  RESULTS
  We found lower membrane excitability of the corticocortical axons and normal intracortical γ-aminobutyric acid inhibition in contrast with what has been described in other forms of primary dystonia. Myoclonus-dystonia patients also shared some common pathophysiological features of dystonia, including enhanced responsiveness of the motor cortex to plasticity induction and abnormal response to cerebellar conditioning as tested by EBCC.
  
  
  CONCLUSIONS
  Specific underlying dysfunctions are associated with the very particular clinical phenotype of M-D and make it a unique entity that stands apart from other primary dystonias.
authors.affiliation: Centre de Neuroimagerie de Recherche, Institut du Cerveau et de la Moelle Épinière, Paris, France2Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche d.
authors.forename: Traian
authors.initials: T
authors.lastname: Popa
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche de Neurosciences-Unité Mixte de Recherche 7225, Université Pierre et Marie Curie-Paris 6 UMR_S975.
authors.forename: Paolo
authors.initials: P
authors.lastname: Milani
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche de Neurosciences-Unité Mixte de Recherche 7225, Université Pierre et Marie Curie-Paris 6 UMR_S975.
authors.forename: Aliénor
authors.initials: A
authors.lastname: Richard
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche de Neurosciences-Unité Mixte de Recherche 7225, Université Pierre et Marie Curie-Paris 6 UMR_S975.
authors.forename: Cécile
authors.initials: C
authors.lastname: Hubsch
authors.affiliation: Centre d'Investigation Clinique Pitié Neurosciences 1422, Hôpital Pitié-Salpêtrière, Paris, France.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Brochard
authors.affiliation: Centre de Compétence des Maladies Neurologiques Génétiques Rares, Service de Neurologie, Hôpital de Hautepierre, Strasbourg, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Tranchant
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, England.
authors.forename: Anna
authors.initials: A
authors.lastname: Sadnicka
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, England.
authors.forename: John
authors.initials: J
authors.lastname: Rothwell
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche de Neurosciences-Unité Mixte de Recherche 7225, Université Pierre et Marie Curie-Paris 6 UMR_S975.
authors.forename: Marie
authors.initials: M
authors.lastname: Vidailhet
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche de Neurosciences-Unité Mixte de Recherche 7225, Université Pierre et Marie Curie-Paris 6 UMR_S975.
authors.forename: Sabine
authors.initials: S
authors.lastname: Meunier
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Institut National de la Santé et de la Recherche Médicale U1127, Centre de Recherche de Neurosciences-Unité Mixte de Recherche 7225, Université Pierre et Marie Curie-Paris 6 UMR_S975.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Roze
mesh_terms: D000328:Adult; D003215:Conditioning, Eyelid / Q000502:physiology*; D020821:Dystonic Disorders / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D049031:Sarcoglycans / Q000235:genetics; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult
chemical_list: C526572:SGCE protein, human; D049031:Sarcoglycans