title: Optimal control of reaching is disturbed in complex regional pain syndrome: a single-case study.
abstract: OBJECTIVE
  Disturbance of goal-directed motor control may cause or exacerbate pathological pain in patients with complex regional pain syndrome (CRPS). We conducted a single-case study about motor control involved in reaching with a patient with CRPS in an upper limb.
  
  
  METHODS
  Using a three-dimensional measurement system, we recorded reaching movement trajectories of the intact and affected hand before and after pain alleviation by therapeutic nerve blockade. We assessed degrees of tremor in the acceleration phase (from start until maximum peak velocity) and the deceleration phase (from maximum peak velocity until goal). To quantify the smoothness of reaching movements, we analyzed the curves of the trajectories during the initial movement phase (from start and maximum peak acceleration).
  
  
  RESULTS
  The results showed that the tremor of the affected hand was greater than that of the intact hand during the deceleration phase, both before and after pain alleviation. Reaching trajectories of the intact hand smoothly traced curves convexed toward the intact side, while those of the affected hand represented unnaturally rectilinear functions associated with the loss of smooth movements. Further, these unnatural trajectories partially recovered after pain alleviation.
  
  
  CONCLUSIONS
  Disturbance of sensorimotor integration and pain-related fear might affect goal-directed motor control in CRPS patients.
authors.affiliation: Neurorehabilitation Research Center, Kio University, Nara.
authors.forename: Michihiro
authors.initials: M
authors.lastname: Osumi
authors.affiliation: Department of Pain and Palliative Medicine, The University of Tokyo Hospital.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Sumitani
authors.affiliation: Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.
authors.forename: Shin-Ichiro
authors.initials: SI
authors.lastname: Kumagaya
authors.affiliation: Neurorehabilitation Research Center, Kio University, Nara.
authors.forename: Shu
authors.initials: S
authors.lastname: Morioka
keywords: complex regional pain syndrome; motor control; reaching movement; sensorimotor integration