Effect of visual information on step-tracking movements in patients with intention tremor due to multiple sclerosis

Abstract

The effect of visual information on step-tracking movements was studied in 18 patients with intention tremor due to multiple sclerosis (MS) and 15 healthy controls. Parricipants performed a slow wrist step-tracking task with stationary targets under five visual feedback conditions. The display of the target and movement cues was selectively withdrawn to examine the effects of visual information on intention tremor and movement accuracy. Results showed that intention tremor was most pronounced when visual display of both target and movement cues was available. Withdrawing visual information of the limb movement reduced tremor more than withdrawing the visual display of the target cues. Both the patient and control group was less accurate when the display of limb movement was occluded. Patients, however, were more dependent on visual information of the limb movement for accurate motor performance than healthy controls. When the visual display of the limb movement was partially occluded between or near to the targets, tremor decreased without deterioration of movement accuracy.

Digitised spirography as an evaluation tool for intention tremor in multiple sclerosis

“…This observation may be related to the nature of the circular drawing task, which is a visually guided movement requiring continuous error correction. Our previous studies (Liu et al, 1997;Feys et al, 2003Feys et al, , 2006 showed that MS tremor is clearly enhanced when visual information of both target and hand position is available, most likely because the induction of voluntary error correction movements leads to an increase of overall involuntary intention tremor amplitude. During circular spiral drawing, it is thought that MS patients visually detected spatial errors easier in the radial direction, perpendicular to the circle template, rather than in its tangential direction.…”

Effects of peripheral cooling on intention tremor in multiple sclerosis

“…The cooling interventions applied in our present study are thought to lead to substantial functional improvements, because the tremor measures of the step tracking task have been shown to be closely related to clinical ratings of intention tremor during the finger to nose test or pouring water. 15 However, it must be noted that the reported cooling interventions may be less effective in patients with MS who have considerable proximal tremor during the performance of functional activities requiring movements in the proximal joints. It is also unclear whether patients with MS who have very severe tremor would experience the same benefits of the moderate cooling intervention as was reported in our study.…”

“…Step tracking task The wrist step tracking task and data analysis were identical to those in previous studies, 15 and are summarised here. Participants were seated in front of a computer screen with their forearm and hand placed in a wrist orthosis, which was fixed to the arm of the chair.…”

“…15 23 24 Twenty three arms of 18 patients were subjected to the deep cooling intervention, whereas 11 arms of nine patients also underwent the moderate cooling intervention during a separate test session. Data from six hands, equally divided between both cooling conditions, were not included in the data analysis because their very large tremor amplitudes prevented an adequate rhythmical execution of the task and impeded the accurate mathematical determination of the start and end of each movement trial.…”

“…14 The step tracking task was previously shown to be valid for assessing intention tremor. 15 The cooling intervention was restricted to the forearm affecting the wrist flexors and extensor muscles, which are primarily involved in the wrist step tracking task. The wrist joint was not included to avoid substantial cooling of the wrist joint or nearby skin receptors.…”