Objective: To investigate whether proprioceptive information generated from the neck is impaired in patients with idiopathic Cervical Dystonia (CD).

Background: CD is a focal dystonia characterized by involuntary contractions of the neck muscles leading to an abnormal head position and pain. In order to obtain functional stability of the neck, afferent proprioceptive information of the neck is integrated with visual, vestibular and somatosensory information to keep the head stable. If proprioceptive afferent information from the neck is impaired, this could lead to new insights in the pathophysiology of CD.

Methods: Head repositioning accuracy is the method of choice to measure neck proprioception and is expressed in joint position error (JPE, measured in °). The JPE of 68 controls (mean age 54,48 year ±16,01) was measured and compared with that of 24 patients with CD regularly receiving botulinum toxin treatment (mean age 59,25 year ±13,96) with a mean disease duration of 13,06 year (±8,7). JPE measurements were made via 3D motion analysis using an infrared camera system at 100Hz (8 camera’s, VICON T10, Oxford Metrics, Oxford). Rigid plates with reflective markers were placed on the head and the sternum. A head repositioning task was analyzed in which blindfolded patients were instructed to reposition the head to a neutral, comfortable position after performing a flexion, extension, left rotation and right rotation movement of the head. Movement angles of the neck were calculated using Euler/Cardan rotations of the head segment relative to the sternum segment. The mean absolute JPE from 10 trials was calculated as the mean difference in neck angle between the starting and ending position.

Results: Results were not normally distributed, therefore the Mann Whitney U Test was conducted with a Bonferroni correction. The median of the absolute JPE was significantly larger (p< 0.0125) in patients than in a control population after performing a flexion movement (4,66° vs 3,03°), left rotation (3,69° vs 2,05°) and right rotation (3,37° vs 2,22°). No correlation was found between the larger JPE and age or gender of the patients, presence of tremor, severity or duration of CD.

Conclusions: To our knowledge, this is the first study analyzing joint position sense in CD. Our data adds up to recent research that afferent proprioceptive information generated from the neck is impaired in patients with CD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neck-proprioception-is-impaired-in-patients-with-idiopathic-cervical-dystonia/