title: Neural and nonneural contributions to wrist rigidity in Parkinson's disease: an explorative study using the NeuroFlexor.
abstract: OBJECTIVE
  The NeuroFlexor is a novel method incorporating a biomechanical model for the measurement of neural and nonneural contributions to resistance induced by passive stretch. In this study, we used the NeuroFlexor method to explore components of passive movement resistance in the wrist and finger muscles in subjects with Parkinson's disease (PD).
  
  
  METHODS
  A cross-sectional comparison was performed in twenty-five subjects with PD with clinically identified rigidity and 14 controls. Neural (NC), elastic (EC), and viscous (VC) components of the resistance to passive extension of the wrist were calculated using the NeuroFlexor. Measurements were repeated during a contralateral activation maneuver.
  
  
  RESULTS
  PD subjects showed greater total resistance (P < 0.001) and NC (P = 0.002) compared to controls. EC and VC did not differ significantly between groups. Contralateral activation maneuver resulted in increased NC in the PD group but this increase was due to increased resting tension. Total resistance and NC correlated with clinical ratings of rigidity and with bradykinesia.
  
  
  CONCLUSIONS
  The findings suggest that stretch induced reflex activity, but not nonneural resistance, is the major contributor to rigidity in wrist muscles in PD. The NeuroFlexor is a potentially valuable clinical and research tool for quantification of rigidity.
authors: Department of Neuroscience, Rehabilitation Medicine, Uppsala University, 75105 Uppsala, Sweden.
authors: H
authors: H
authors: Zetterberg
authors: Department of Neuroscience, Rehabilitation Medicine, Uppsala University, 75105 Uppsala, Sweden.
authors: G E
authors: GE
authors: Frykberg
authors: Department of Women's and Children's Health, Karolinska Institutet, 17177 Stockholm, Sweden.
authors: J
authors: J
authors: Gäverth
authors: Department of Clinical Sciences, Karolinska Institutet, Danderyd University Hospital, 18288 Stockholm, Sweden ; FR3636 CNRS, Université Paris Descartes, Sorbonne Paris Cité, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France.
authors: P G
authors: PG
authors: Lindberg
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009127:Muscle Rigidity / Q000473:pathology / Q000503:physiopathology*; D010300:Parkinson Disease / Q000473:pathology / Q000503:physiopathology*; D014953:Wrist / Q000473:pathology / Q000503:physiopathology*