Changes in the Relationship Between Movement Velocity and Movement Distance in Primary Focal Hand Dystonia

Abstract

The authors examined the relationship between movement velocity and distance and the associated muscle activation patterns in 18 individuals with focal hand dystonia (FHD) compared with a control group of 18 individuals with no known neuromuscular condition. Participants performed targeted voluntary wrist and elbow flexion movements as fast as possible across 5 movement distances. Individuals with FHD were slower than controls across all distances, and this difference was accentuated for longer movements. Muscle activation patterns were triphasic in the majority of individuals with FHD, and muscle activation scaled with distance in a similar manner to controls. Cocontraction did not explain movement slowing in individuals with dystonia, but there was a trend toward underactivation of the 1st agonist burst in the dystonic group. The authors concluded that slowness is a consistent feature of voluntary movement in FHD and is present even in the absence of dystonic posturing. Underactivation of the 1st agonist burst appears to be the most likely reason to explain slowing. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscriptsuggests that dystonia is a disorder that also affects voluntary movement control, even in the absence of dystonic muscle spasms. Individuals with dystonia are slower than individuals with no known neuro-muscular condition at both wrist (MacKinnon, Velickovic, Drafta, Hesquijarosa, & Brin, 2004) and elbow joints (van der Kamp et al., 1989) during movement with one degree of freedom and during whole-arm movement (Agostino, Berardelli, Formica, Accornero, & Manfredi, 1992;Curra et al., 2000;Inzelberg, Flash, & Korczyn, 1990;Inzelberg, Flash, Schechtman, & Korczyn, 1995). However, single-joint studies have been concerned with movement distances of 30° or less, and researchers have examined no more than two target distances within a study (15° and 30°;van der Kamp et al., 1989). When ballistic selfpaced movements are performed over a wide range of movement distances in individuals with no known neuromuscular condition, movement velocity scales with movement distance. This relationship is approximately linear (Bahill, Clark, & Stark, 1975;Newell, Hancock, & Robertson, 1984). Pfann, Buchman, Comella, and Corcos (2001) showed the slope of the relationship between peak velocity and target distance to be impaired in basal ganglia disorders such as Parkinson's disease. Because dystonia is related to abnormal basal ganglia functioning, it is of interest to know whether the relationship between peak velocity and movement distance is also impaired in primary dystonia. It is also not clear whether muscle activation patterns are modulated appropriately across movement distance in individuals with dystonia.In addition to deficits in movement control, deficits in force control have also been shown in individuals with focal dystonia even when they do not manifest dystonic symptoms during the performance of a task. For example, in the absence of dystonic posturing, individuals with FHD ...

Effects of cerebellar theta-burst stimulation on arm and neck movement kinematics in patients with focal dystonia

“…Moreover, we found no significant group difference in terms of the quality of the movement, i.e., straightness, smoothness and overshooting. Our kinematic results are in contrast to those of previous studies showing the slowness of movement in patients with dystonia (Agostino et al, 1992; Curra et al, 2000; Prodoehl et al, 2008). Differences in results, however, may reflect the different movements analysed or the clinical heterogeneity of patients enrolled in the various studies.…”

Effects of visual gain on force control at the elbow and ankle

“…This algorithm has been used during movement (Vaillancourt et al 2004; Prodoehl et al 2008) and force production tasks (Prodoehl et al 2006). …”

Emerging concepts on bradykinesia in non‐parkinsonian conditions

“…Co-contraction activity between agonist and antagonist muscles may have a detrimental effect on the execution of voluntary movement, for example, in FHD patients performing the task triggering cramps [21,70]. Bradykinesia in dystonia, however, has also been demon- between antagonist muscle groups cannot be clearly identified [71], as well as in non-dystonic body segments, that is, where there is no co-contraction activity. Weakness and increased muscle tone may also potentially explain the presence of bradykinesia in patients with ALS, primary lateral sclerosis, stroke, and MS [132,137,139,187], although studies specifically addressing this issue are lacking.…”

“…Neurophysiological investigations in patients with generalized dystonia and FHD have variably shown that movement preparation can be abnormally prolonged [52][53][54][55][56][57][58][59][60]63,67,69]. Kinematic and electromyographic (EMG) recordings have demonstrated that in comparison with healthy subjects, patients performed single and multijoint arm movements with slower velocity and reduced amplitude, with co-contraction of agonist and antagonist muscles [21,65,70] or reduced contraction of muscle activity [66,71]. Bradykinesia has also been observed during reaching arm movements in patients with idiopathic torsion dystonia [61] or during sequential arm movements and finger-tapping in patients with generalized dystonia and FHD [6,62,[72][73][74], although these results are not always consistent [75][76][77] and no studies have specifically investigated sequence effect in dystonic patients.…”