Smoothness of movement in idiopathic cervical dystonia

Abstract

Smoothness (i.e. non-intermittency) of movement is a clinically important property of the voluntary movement with accuracy and proper speed. Resting head position and head voluntary movements are impaired in cervical dystonia. The current work aims to evaluate if the smoothness of voluntary head rotations is reduced in this disease. Twenty-six cervical dystonia patients and 26 controls completed rightward and leftward head rotations. Patients’ movements were differentiated into “towards-dystonia” (rotation accentuated the torticollis) and “away-dystonia”. Smoothness was quantified by the angular jerk and arc length of the spectrum of angular speed (i.e. SPARC, arbitrary units). Movement amplitude (mean, 95% CI) on the horizontal plane was larger in controls (63.8°, 58.3°–69.2°) than patients when moving towards-dystonia (52.8°, 46.3°–59.4°; P = 0.006). Controls’ movements (49.4°/s, 41.9–56.9°/s) were faster than movements towards-dystonia (31.6°/s, 25.2–37.9°/s; P < 0.001) and away-dystonia (29.2°/s, 22.9–35.5°/s; P < 0.001). After taking into account the different amplitude and speed, SPARC-derived (but not jerk-derived) indices showed reduced smoothness in patients rotating away-dystonia (1.48, 1.35–1.61) compared to controls (1.88, 1.72–2.03; P < 0.001). Poor smoothness is a motor disturbance independent of movement amplitude and speed in cervical dystonia. Therefore, it should be assessed when evaluating this disease, its progression, and treatments.

Evaluation of Gait Smoothness in Patients with Stroke Undergoing Rehabilitation: Comparison between Two Metrics

“…Given that our protocol involved large movements, this interpretation may also help to explain our findings. In addition, it is possible that linear motions (as in our study) and rotational movements (as in the study by Caronni et al [ 32 ]) may require different metrics to evaluate smoothness. This corroborates the hypothesis that a better metric does not exist, but it should be selected according to the analyzed movement, as well as, the investigated cohort and the employed sensors to acquire the BCoM kinematics.…”

“…Smoothness, which refers to a subject’s capacity to produce continuous or non-intermittent movements [ 31 ], is a characteristic of voluntary healthy movements [ 32 ]. In this study, using kinematic data obtained from an optoelectronic system, the gold standard for motion analysis, we analyzed two metrics for assessing gait smoothness in two samples of patients with stroke (subacute and chronic patients) undergoing rehabilitation.…”

“…According to the above, the Literature seems to suggest that different metrics could be more suitable for different movements or patients. Indeed, in a study by Caronni et al [ 32 ], the authors investigated differences in the smoothness of head movements between healthy subjects and patients with idiopathic cervical dystonia, using the same indices here proposed, but obtaining opposite results: in fact, in their study, only the SPARC was able to distinguish between healthy subject and patient with cervical dystonia. The authors interpreted the better behavior of the SPARC in light of the study by Singh et al [ 35 ], which suggested that the SPARC is more sensitive to changes in smaller movements.…”

Effects of Upper Limb Robot-Assisted Rehabilitation Compared with Conventional Therapy in Patients with Stroke: Preliminary Results on a Daily Task Assessed Using Motion Analysis

“…Furthermore, as a result of the rehabilitation intervention, these submovements gradually overlap and integrate to generate a more fluid movement over time [ 44 ]. When comparing multiple smoothness metrics, most of which are based on the jerk (the third derivative of the displacement) or the spectral arc length, the results are often inconsistent and, sometimes, opposite [ 45 , 46 , 47 , 48 ]. Regardless of the provided intervention, both the LDLJ and SPARC concurred in our research that patients showed a statistically significant improvement in movement smoothness after the rehabilitation in two out of the three analyzed phases.…”

Cervical Proprioception Assessed through Targeted Head Repositioning: Validation of a Clinical Test Based on Optoelectronic Measures

“…Each participant was asked to move repeatedly in the four directions (right and left rotations, extension, flexion) with assistance and then autonomously (see below). An optoelectronic procedure was adopted for measuring head rotations, such as in other studies for neck kinematics [ 29 , 35 , 40 , 41 , 42 ].…”