Dynamic head-neck stabilization in cervical dystonia.
BACKGROUND
Effective sensorimotor integration is essential to modulate (adapt) neck stabilization strategies in response to varying tasks and disturbances. This study evaluates the hypothesis that relative to healthy controls cervical dystonia patients have an impaired ability to modulate afferent feedback for neck stabilization with changes in the frequency content of mechanical perturbations.


METHODS
We applied anterior-posterior displacement perturbations (110s) on the torso of seated subjects, while recording head-neck kinematics and muscular activity. We compared low bandwidth (0.2-1.2Hz) and high bandwidth (0.2-8Hz) perturbations where our previous research showed a profound modulation of stabilization strategies in healthy subjects. Cervical dystonia patients and age matched controls performed two tasks: (1) maintain head forward posture and (2) allow dystonia to dictate head posture.


RESULTS
Patients and controls demonstrated similar kinematic and muscular responses. Patient modulation was similar to that of healthy controls (P>0.05); neck stiffness and afferent feedback decreased with high bandwidth perturbations. During the head forward task patients had an increased neck stiffness relative to controls (P<0.05), due to increased afferent feedback.


CONCLUSIONS
The unaffected modulation of head-neck stabilization (both kinematic and muscular) in patients with cervical dystonia does not support the hypothesis of impaired afferent feedback modulation for neck stabilization.
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands; Department of Neuroscience, Erasmus University Medical Centre, Rotterdam, The Netherlands. Electronic address: p.forbes@erasmusmc.nl.
Patrick A
PA
Forbes
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands.
Edo
E
de Bruijn
Department of Neurology and Clinical Neurophysiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
Sebastiaan W R
SW
Nijmeijer
Department of Neurology and Clinical Neurophysiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
Johannes H T M
JH
Koelman
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands; Laboratory of Biomechanical Engineering, Institute for Biomedical Technology and Technical Medicine (MIRA), University of Twente, Enschede, The Netherlands.
Frans C T
FC
van der Helm
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands; Laboratory of Biomechanical Engineering, Institute for Biomedical Technology and Technical Medicine (MIRA), University of Twente, Enschede, The Netherlands.
Alfred C
AC
Schouten
Department of Neurology and Clinical Neurophysiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Department of Neurology, University Medical Centre Groningen (UMCG), University of Groningen, Groningen, The Netherlands.
Marina A J
MA
Tijssen
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands.
Riender
R
Happee
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006257:Head / Q000502:physiology; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000502:physiology; D009334:Neck Muscles / Q000502:physiology; D011187:Posture / Q000502:physiology; D012018:Reflex / Q000502:physiology; D014103:Torticollis / Q000503:physiopathology*
Cervical dystonia; Dystonic posture; Head-neck stabilization; Neck afferent feedback modulation; Sensorimotor integration