title: Distribution and Coexistence of Myoclonus and Dystonia as Clinical Predictors of SGCE Mutation Status: A Pilot Study.
abstract: BACKGROUND
  Myoclonus-dystonia (M-D) is a young onset movement disorder typically involving myoclonus and dystonia of the upper body. A proportion of the cases are caused by mutations to the autosomal dominantly inherited, maternally imprinted, epsilon-sarcoglycan gene (SGCE). Despite several sets of diagnostic criteria, identification of patients most likely to have an SGCE mutation remains difficult.
  
  
  METHODS
  Forty consecutive patients meeting pre-existing diagnostic clinical criteria for M-D underwent a standardized clinical examination (20 SGCE mutation positive and 20 negative). Each video was reviewed and systematically scored by two assessors blinded to mutation status. In addition, the presence and coexistence of myoclonus and dystonia was recorded in four body regions (neck, arms, legs, and trunk) at rest and with action.
  
  
  RESULTS
  Thirty-nine patients were included in the study (one case was excluded owing to insufficient video footage). Based on previously proposed diagnostic criteria, patients were subdivided into 24 "definite," 5 "probable," and 10 "possible" M-D. Motor symptom severity was higher in the SGCE mutation-negative group. Myoclonus and dystonia were most commonly observed in the neck and upper limbs of both groups. Truncal dystonia with action was significantly seen more in the mutation-negative group (p < 0.05). Coexistence of myoclonus and dystonia in the same body part with action was more commonly seen in the mutation-negative cohort (p < 0.05).
  
  
  CONCLUSIONS
  Truncal action dystonia and coexistence of myoclonus and dystonia in the same body part with action might suggest the presence of an alternative mutation in patients with M-D.
authors.affiliation: Department of Neurology, University Medical Center Groningen , Groningen , Netherlands.
authors.forename: Rodi
authors.initials: R
authors.lastname: Zutt
authors.affiliation: Department of Neurology, Academic Medical Center, University of Amsterdam , Amsterdam , Netherlands.
authors.forename: Joke M
authors.initials: JM
authors.lastname: Dijk
authors.affiliation: Department of Neurology, University Medical Center Groningen, Groningen, Netherlands; MRC Centre for Neuropsychiatric Genetics and Genomics, Institute of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, UK.
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Peall
authors.affiliation: Department of Neurology, Academic Medical Center, University of Amsterdam , Amsterdam , Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Speelman
authors.affiliation: Department of Neurology, Academic Medical Center, University of Amsterdam , Amsterdam , Netherlands.
authors.forename: Yasmine E M
authors.initials: YE
authors.lastname: Dreissen
authors.affiliation: Department of Neurology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands; Department of Neurology, Haga Teaching Hospital, Den Haag, Netherlands.
authors.forename: Maria Fiorella
authors.initials: MF
authors.lastname: Contarino
authors.affiliation: Department of Neurology, University Medical Center Groningen , Groningen , Netherlands.
authors.forename: Marina A J
authors.initials: MA
authors.lastname: Tijssen
keywords: SGCE mutations; dystonia; motor characteristics; myoclonus; myoclonus–dystonia