Short communicationIn idiopathic cervical dystonia movement direction is inaccurate when reaching in unusual workspaces☆
Introduction
The knowledge about mechanism underlying abnormal motor control in idiopathic dystonia is still limited. Kinematic studies have disclosed abnormalities in patients with dystonia [1], [2], [3] that suggest an impairment of both proprioception and motor programming, not only in the affected body parts, but also in unaffected segments [2], [3], [4].
In reaching movements, the spatial location of the target is remapped from retinotopic into egocentric coordinates, then target information is combined with hand position information in order to form a simplified hand-centered plan of the intended movement trajectory as an extent and direction in extrinsic space [5]. One of the most important kinematic measures reflecting trajectory planning is movement direction [5], which is indeed encoded by specific cortical neurons, whose discharge pattern is closely related to movement direction [6]. When performing reaching movements in everyday activities, the initial hand position is usually close to the midline in front of the subject’s body.
Performing reaching movements with the right arm displaced to the right and out of sight can be considered to happen very rarely, since usually the trunk is rotated toward the target. We define “unusual area of work” as the condition when the right outstretched arm performs a reaching movement without the subject’s trunk facing it. In this setting, normal subjects aim their movements with a rightward directional error [5]. It has been hypothesised that this directional bias is caused by an impaired representation of limb configuration, which hampers the actual movement vector [5]. Our objective is to understand how patients affected by idiopathic cervical dystonia perform reaching movements in an unusual area of work to test the possible occurrence of defective spatial representation of the moving arm
Section snippets
Subjects
The same subjects involved in our previous study [2] have been included, consisting in 10 patients, 5 men and 5 women, with idiopathic cervical dystonia (CD) (age, mean ± SD: 50.5 ± 10.1 years) and 10 aged-matched normal controls (NC), 4 men and 6 women (age 46.4 ± 12.6 years). All subjects were right-handed, without cognitive impairment (MMSE > 26) or psychiatric diseases. Mobility at the elbow and shoulder joints was normal and painless in all participants. No segmental spread of dystonia was
Head rotation
Head rotation, considered as absolute deviation from the midline, was 38 ± 9° (SE). The direction of the rotation was leftward in 6 patients and rightward in 4. No significant difference was found between head rotation measured in the central and lateral position just before starting the tasks.
Kinematic parameters
We evaluated the normalized hand path, reversal lag, reaction time, movement extent, amplitudes of peak of velocity and peak of acceleration, movement time and symmetry index in dystonic patients and
Discussion
In this study we analyze the motor performance of dystonic subjects while performing reaching movements in an unusual area of work. Patients and controls have been evaluated not only with their right arm aligned to the sagittal midline (central position), but also displaced to the right (lateral position). We can consider the central position, with the arm just in front of patient’s body, as the position usually adopted during everyday tasks; all subjects are used to performing most reaching
References (12)
- et al.
Changed patterns of cerebral activation related to clinically normal hand movement in cervical dystonia
Clin Neurol Neurosurg
(2008) - et al.
Mental rotation of body parts and non-corporeal objects in patients with idiopathic cervical dystonia
Neuropsychologia
(2007) - et al.
Kinematic properties of upper limb trajectories in idiopathic torsion dystonia
J Neurol Neurosurg Psychiatry
(1995) - et al.
Cervical dystonia affects aimed movements of nondystonic segments
Mov Disord
(2009) - et al.
Kinesthesia is impaired in focal dystonia
Mov Disord
(2006) - et al.
Learning a visuomotor transformation in a local area of work space produces directional biases in other areas
J Neurophysiol
(1995)
Cited by (15)
Impairments of balance, stepping reactions and gait in people with cervical dystonia
2017, Gait and PostureCitation Excerpt :Clinically people with CD often report that fear of falling curtails their physical activity [17]. To date there is little understanding as to whether people with CD experience balance and gait deficits, even though they are known to have issues with proprioceptive and vestibular function [18–21] and impaired vision secondary to the twisted head posture. Growing evidence for the involvement of the cerebellum in CD suggests there may be an impact on balance and function given the importance of the cerebellum in motor coordination and gait.
Sensory-motor integration in focal dystonia
2015, NeuropsychologiaCitation Excerpt :Moreover, temporal velocity profiles were asymmetrical and reversal lags between out- and back-strokes were longer in cervical dystonia patients. It was suggested that this deficit could be due to an error in the spatial representation of the hand location or to a failure in integrating proprioceptive information with the motor output (Marinelli et al., 2011). Section 2 summarizes the CNS structures involved in sensory processing, cognitive movement representation, and sensory-motor integration.
Pointing in cervical dystonia patients
2023, Frontiers in Systems NeuroscienceA cross-sectional study of walking, balance and upper limb assessment scales in people with cervical dystonia
2021, Journal of Neural TransmissionFeedback-dependent neuronal properties make focal dystonias so focal
2021, European Journal of Neuroscience
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The review of this paper was entirely handled by an Associate Editor, V. Bonifati.