title: Interactions between voluntary head control and neck proprioceptive reflexes in cervical dystonia.
abstract: BACKGROUND
  To investigate deficiencies in mechanisms of sensorimotor processing and reflexive-voluntary interactions leading to the impaired head position control in primary cervical dystonia.
  
  
  METHODS
  Thirteen patients and 23 healthy controls were subjected to transient, low amplitude, low velocity head-on-trunk, trunk-under-head and whole-body rotations in the horizontal plane. With the instruction not to resist the imposed displacements, resistance to horizontal neck deflections was evaluated.
  
  
  RESULTS
  Patients exhibited a torque offset (bias) in the direction of torticollis before stimulus application. While controls reduced and occasionally eliminated completely the initial resistance to head-to-trunk rotations, torque in patients increased throughout displacements. Change of resistance relative to baseline in patients was, however, symmetrical, i.e. independent of torticollis direction. Spontaneous torque fluctuations were significantly larger in patients. Strong correlations existed among these abnormal findings.
  
  
  CONCLUSIONS
  Patients' ability to manipulate normal postural reactions to head-trunk rotations is impaired. The deficit is bilateral and correlates with the degree of abnormal posture. The present study extends previous work on reflexive-voluntary interactions and provides evidence that malfunctioning proprioceptive feedback may contribute to the pathophysiology of cervical dystonia.
authors.affiliation: Neurologische Klinik, Neurozentrum, Universität Freiburg, Breisacherstraße 64, 79106 Freiburg, Germany; Department of Physiology and Clinical Neurophysiology, School of Health Sciences, University of Athens, Tetrapoleos 8, 11527 Goudi, Athens, Greece. Electronic address: danastas@nurs.uoa.gr.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Anastasopoulos
authors.affiliation: Neurologische Klinik, Neurozentrum, Universität Freiburg, Breisacherstraße 64, 79106 Freiburg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Maurer
authors.affiliation: Neurologische Klinik, Neurozentrum, Universität Freiburg, Breisacherstraße 64, 79106 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mergner
mesh_terms: D000328:Adult; D001288:Attention; D005260:Female; D006257:Head / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000294:innervation*; D004856:Postural Balance / Q000502:physiology; D011434:Proprioception / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012399:Rotation; D012678:Sensation Disorders / Q000209:etiology*; D013028:Space Perception; D019415:Torque; D014103:Torticollis / Q000150:complications*; D055815:Young Adult
keywords: Basal ganglia; Dystonia; Motor control; Torticollis