G. Zilvold

Relation between stimulation characteristics and clinical outcome in studies using electrical stimulation to improve motor control of the upper extremity in stroke

OBJECTIVE Electrical stimulation can be applied in a variety of ways to the hemiparetic upper extremity following stroke. The aim of this review is to explore the relationship between characteristics of stimulation and the effect of electrical stimulation on the recovery of upper limb motor control following stroke. METHODS A systematic literature search was performed to identify clinical trials evaluating the effect of electrical stimulation on motor control. The reported outcomes were examined to identify a possible relationship between the reported effect and the following characteristics: duration of stimulation, method of stimulation, setting of stimulation parameters, target muscles and stage after stroke. RESULTS Nineteen clinical trials were included, and the results of 22 patient groups were evaluated. A positive effect of electrical stimulation was reported for 13 patient groups. Positive results were more common when electrical stimulation was triggered by voluntary movement rather than when non-triggered electrical stimulation was used. There was no relation between the effect of electrical stimulation and the other characteristics examined. CONCLUSION Triggered electrical stimulation may be more effective than non-triggered electrical stimulation in facilitating upper extremity motor recovery following stroke. It appears that the specific stimulus parameters may not be crucial in determining the effect of electrical stimulation.

Cervical muscle dysfunction in the chronic whiplash associated disorder grade II (WAD-II).

Study Design. In a cross-sectional study, surface electromyography measurements of the upper trapezius muscles were obtained during different functional tasks in patients with a chronic whiplash associated disorder Grade II and healthy control subjects. Objectives. To investigate whether muscle dysfunction of the upper trapezius muscles, as assessed by surface electromyography, can be used to distinguish patients with whiplash associated disorder Grade II from healthy control subjects. Summary of Background Information. In the whiplash associated disorder, there is need to improve the diagnostic tools. Whiplash associated disorder Grade II is characterized by the presence of “musculoskeletal signs.” Surface electromyography to assess these musculoskeletal signs objectively may be a useful tool. Methods. Normalized smoothed rectified electromyography levels of the upper trapezius muscles of patients with whiplash associated disorder Grade II (n = 18) and healthy control subjects (n = 19) were compared during three static postures, during a unilateral dynamic manual exercise, and during relaxation after the manual exercise. Coefficients of variation were computed to identify the measurement condition that discriminated best between the two groups. Results. The most pronounced differences between patients with whiplash associated disorder Grade II and healthy control subjects were found particularly in situations in which the biomechanical load was low. Patients showed higher coactivation levels during physical exercise and a decreased ability to relax muscles after physical exercise. Conclusions. Patients with whiplash associated disorder Grade II can be distinguished from healthy control subjects according to the presence of cervical muscle dysfunction, as assessed by surface electromyography of the upper trapezius muscles. Particularly the decreased ability to relax the trapezius muscles seems to be a promising feature to identify patients with whiplash associated disorder Grade II. Assessment of the muscle (dys)function by surface electromyography offers a refinement of the whiplash associated disorder classification and provides an indication to a suitable therapeutic approach.

Cervical muscle dysfunction in chronic whiplash-associated disorder grade 2: the relevance of the trauma.

Study Design. Surface electromyography measurements of the upper trapezius muscles were performed in patients with a chronic whiplash-associated disorder Grade 2 and those with nonspecific neck pain. Objective. To determine the etiologic relation between acceleration–deceleration trauma and the presence of cervical muscle dysfunction in the chronic stage of whiplash-associated disorder. Summary of Background Information. From a biopsychosocial perspective, the acceleration–deceleration trauma in patients with whiplash-associated disorder is not regarded as a cause of chronicity of neck pain, but rather as a risk factor triggering response systems that contribute to the maintenance of neck pain. One of the contributing factors is dysfunction of the cervical muscles. Considering the limited etiologic significance of the trauma, it is hypothesized that in patients with neck pain, there are no differences in muscle activation patterns between those with and those without a history of an acceleration–deceleration trauma. Methods. Muscle activation patterns, expressed in normalized smooth rectified electromyography levels of the upper trapezius muscles, in patients with whiplash-associated disorder Grade 2 were compared with those of patients with nonspecific neck pain. The outcome parameters were the mean level of muscle activity before and after a physical exercise, the muscle reactivity in response to the exercise, and the time-dependent behavior of muscle activity after the exercise. Results. There were no statistical significant differences in any of the outcome parameters between patients with whiplash-associated disorder Grade 2 and those with nonspecific neck pain. There was only a tendency of higher muscle reactivity in patients with whiplash-associated disorder Grade 2. Conclusions. It appears that the cervical muscle dysfunction in patients with chronic whiplash-associated disorder Grade 2 is not related to the specific trauma mechanism. Rather, cervical muscle dysfunction appears to be a general sign in diverse chronic neck pain syndromes.

Chronic neck pain disability due to an acute whiplash injury.

&NA; Several theories about musculoskeletal pain syndromes such as whiplash‐associated disorder (WAD) suggest that pain and muscle activity interact and may contribute to the chronicity of symptoms. Studies using surface electromyography (sEMG) have demonstrated abnormal muscle activation patterns of the upper trapezius muscles in the chronic stage of WAD (grade II). There are, however, no studies that confirm that these muscle reactions are initiated in the acute stage of WAD, nor that these muscle reactions persist in the transition from acute neck pain to chronic neck pain disability. We analyzed the muscle activation patterns of the upper trapezius muscles in a cohort of 92 subjects with acute neck pain due to a motor vehicle accident (MVA). This cohort was followed up in order to evaluate differences in muscular activation patterns between subjects who have recovered and those subjects who have not recovered following an acute WAD and developed chronic neck pain. sEMG parameters were obtained at 1, 4, 8, 12, and 24 weeks after an MVA. The level of muscle reactivity (the difference in pre‐ and post‐exercise EMG levels) and the level of muscle activity during an isometric and a dynamic task were used as EMG parameters. The results revealed no elevated muscle reactivity either in the acute stage, or during the follow‐up period. The results of both the isometric and dynamic task, showed statistically significant different EMG levels between four neck pain disability subgroups (analysis of variance reaching P‐levels of 0.000), with an inverse relationship between the level of neck pain disability and EMG level. Furthermore, follow‐up assessments of the EMG level during these two tasks, did not show a time related change. In conclusion, in subjects with future disability, the acute stage is characterized by a reorganization of the muscular activation of neck and shoulder muscles, possibly aimed at minimizing the use of painful muscles. This change of motor control, is in accordance with both the (neurophysiological) ‘pain adaptation model’ and (cognitive behavioral) ‘fear avoidance model’.

Use of the NESS Handmaster to restore handfunction in tetraplegia: clinical experiences in ten patients

Objective: To explore possible functional effects of the Handmaster in tetraplegia and to determine suitable patients for the system. Patients: Patients with a cervical spinal cord injury between C4 and C6, motor group 0–3. Important selection criteria were a stable clinical situation and the absence of other medical problems and complications. Design: Ten patients were consecutively selected from the in- and outpatient department of a large rehabilitation hospital in The Netherlands. Each patient was fitted with a Handmaster by a qualified therapist and underwent muscle strength and functional training for at least 2 months. Methods: Functional evaluation comprised the performance of a defined set of tasks and at least one additional task as selected by patients themselves. Tasks were performed both with and without the Handmaster. Finally, patients were asked for their opinion on Handmaster use as well as their willingness to future use. Results: In six patients a stimulated grasp and release with either one or both grasp modes (key- and palmar pinch) of the Handmaster was possible. Four patients could perform the set of tasks using the Handmaster, while they were not able to do so without the Handmaster. Eventually, one patient continued using the Handmaster during ADL at home. Conclusion: The Handmaster has a functional benefit in a limited group of patients with a C5 SCI motor group 0 and 1. Suitable patients should have sufficient shoulder and biceps function combined with absent or weak wrist extensors. Though functional use was the main reason for using the Handmaster, this case series showed that therapeutic use can also be considered. Spinal Cord (2000) 38, 244–249.

Functional electrical stimulation by means of the ‘Ness Handmaster Orthosis’ in chronic stroke patients: an exploratory study

Objective: To gain experience with ‘Ness Handmaster Orthosis’ treatment in chronic stroke patients, to identify suitable patients, and to study the effects of treatment. Design: Exploratory, uncontrolled trial with measurement of motor functions and muscle tone of the upper extremity prior to, during, upon completion, and six weeks after a treatment period. Setting: A rehabilitation centre in the Netherlands. Subjects: Eighteen chronic stroke patients (more than six months post stroke), who exhibited upper extremity dysfunction due to spastic paresis. Intervention: A 10-week therapy programme of functional electrical stimulation by means of the ‘Ness Handmaster Orthosis’. Results: The results of 15 patients were available for analysis. The differences in motor score and muscle tone before and at the end of treatment were statistically significant (p = 0.008 and 0.021, respectively). The follow-up measurements showed that the effects on motor functions and muscle tone decreased after therapy completion. Stratification of the patients in two subgroups indicated that patients with initial high motor scores benefited most during the intervention period. Conclusion: The present study suggests that Handmaster treatment possesses therapeutic opportunities in chronic stroke patients with spastic paresis of the upper extremity.

Electrical stimulation of the upper limb in stroke: stimulation of the extensors of the hand vs. alternate stimulation of flexors and extensors.

de Kroon JR, IJzerman MJ, Lankhorst GJ, Zilvold G: Electrical stimulation of the upper limb in stroke: Stimulation of the extensors of the hand vs. alternate stimulation of flexors and extensors. Am J Phys Med Rehabil 2004;83:592–600. Objective:To investigate whether there is a difference in functional improvement in the affected arm of chronic stroke patients when comparing two methods of electrical stimulation. Design:Explanatory trial in which 30 chronic stroke patients with impaired arm function were randomly allocated to either alternating electrical stimulation of the extensor and flexor muscles of the hand (group A) or electrical stimulation of the extensors only (group B). Primary outcome measure was the Action Research Arm test to assess arm function. Grip strength, Motricity Index, Ashworth Scale, and range of motion of the wrist were secondary outcome measures. Results:Improvement on the Action Research Arm test was 1.0 point in group A and 3.3 points in group B; the difference in functional gain was 2.3 points (95% confidence interval, −1.06 to 5.60). The success rate (i.e., percentage of patients with a clinically relevant improvement of >5.7 points on the Action Research Arm test) was 27% in group B (four patients) and 8% in group A (one patient). The differences in functional gain and success rate were not statistically significant, neither were the differences between the two groups on the secondary outcome measures. Conclusion:The difference between the two stimulation strategies was not statistically significant.

Artificial-reflex stimulation for FES-induced standing with minimum quadriceps force

A control strategy is proposed to decrease quadriceps activity during standing. Modified on/off (or artificial reflex) control is used: a non-numerical or finite-state control scheme based on feedback of knee angle and angular velocity. The control strategy is evaluated in paraplegic patients in an experimental setup using transcutaneous stimulation. The stability of the system and its sensitivity to various control parameters are determined. It is concluded that the control scheme will enable reduction of muscle force independent of additional mechanical bracing or specific posture, and may result in continuous dynamic activation of muscle.

Low-level finite state control of knee joint in paraplegic standing

Low-level finite state (locked-unlocked) control is compared with open-loop stimulation of the knee extensor muscles in functional electrical stimulation (FES) induced paraplegic standing. The parameters were: duration of standing, relative torque loss in knee extensor muscles, knee angle stability, average stimulus output and average arm effort during standing. To investigate the impact of external mechanical conditions on controller performance, experiments were performed both under the condition of a freely moving ankle joint and of a mechanically stabilized ankle joint. Finite state control resulted in a 2.5 to 12 times increase of standing duration or in a 1.5 to 5 times decrease of relative torque loss in comparison with open-loop stimulation. Finite state control induced a limit cycle oscillation in the knee joint. Average maximum knee flexion was 6.2 degrees without ankle bracing, and half that value with ankle bracing. Average arm support was 13.9 and 7.5% of the body weight without and with ankle bracing respectively.

The influence of the reciprocal hip joint link in the Advanced Reciprocating Gait Orthosis on standing performance in paraplegia

The effect of reciprocally linking the hip hinges of a hip-knee-ankle-foot orthosis on standing performance was studied in a comparative trial of the Advanced Reciprocating Gait Orthosis (ARGO) and an ARGO in which the Bowden cable was removed (A_GO). Six male subjects with spinal cord injury (SCI) at T4 to T12 level participated in the study, which was conducted using a single case experimental design. Standing balance, the ability to handle balance disturbances (standing stability), and the performance of a functional hand task during standing were assessed in both orthosis configurations in the order A_GO-ARGO-A_GO-ARGO. No significant differences with respect to standing performance were found for the two orthosis configurations. However, the results indicate that the crutch force needed for maintaining balance during various tasks, especially for quiet standing with two crutches, may be much higher in the orthosis without Bowden cable. Therefore, it is very likely that the reciprocal hip joint link in the ARGO provides a substantial and clinically relevant reduction of upper body effort required for standing under functional conditions.