Påvel G. Lindberg

Effects of passive-active movement training on upper limb motor function and cortical activation in chronic patients with stroke: a pilot study.

OBJECTIVE To explore how repetitive passive-active movement training effects upper limb motor function and cortical activation in patients with stroke. DESIGN Single-group treatment trial with baseline comparisons. PATIENTS Ten chronic patients with stroke with paresis of the upper limb. METHODS Assessments were performed during a 4-week baseline period before and once after 4 weeks of training using the Motor Assessment Scale of the upper limb, Nine Hole Peg Test, goniometer for range of movement and the modified Ashworth scale for muscle tone. Two patients underwent functional magnetic resonance imaging pre- and post-training. The treatment consisted of daily sessions of repeated functional reaching and grasping movements guided passively and attempted actively during 4 weeks. RESULTS The group improved in range of motion and Motor Assessment Scale scores. Subjects reported improvements in a variety of daily tasks requiring the use of the affected upper limb. Increases in cortical activation in prefrontal and sensorimotor areas were observed in parallel with improvements of upper limb motor function in the 2 patients scanned. CONCLUSION The 4-week training programme improved hand motor function and ability. Cortical activation on functional magnetic resonance imaging changed in parallel suggesting reorganization of areas related to movements of the paretic limb.

Validation of a New Biomechanical Model to Measure Muscle Tone in Spastic Muscles

Background. There is no easy and reliable method to measure spasticity, although it is a common and important symptom after a brain injury. Objective. The aim of this study was to develop and validate a new method to measure spasticity that can be easily used in clinical practice. Methods. A biomechanical model was created to estimate the components of the force resisting passive hand extension, namely (a) inertia (IC), (b) elasticity (EC), (c) viscosity (VC), and (d) neural components (NC). The model was validated in chronic stroke patients with varying degree of hand spasticity. Electromyography (EMG) was recorded to measure the muscle activity induced by the passive stretch. Results. The model was validated in 3 ways: (a) NC was reduced after an ischemic nerve block, (b) NC correlated with the integrated EMG across subjects and in the same subject during the ischemic nerve block, and (c) NC was velocity dependent. In addition, the total resisting force and NC correlated with the modified Ashworth score. According to the model, the neural and nonneural components varied between patients. In most of the patients, but not in all, the NC dominated. Conclusions. The results suggest that the model allows valid measurement of spasticity in the upper extremity of chronic stroke patients and that it can be used to separate the neural component induced by the stretch reflex from resistance caused by altered muscle properties.

Use-Dependent Up- and Down-Regulation of Sensorimotor Brain Circuits in Stroke Patients

Objective. To examine whether cerebral activity during passive movements decreases with time after stroke, and if reduced activity in the representation for the upper extremity can be reversed with training. Methods. Brain activity was measured by functional magnetic resonance imaging (fMRI) during passive wrist flexion-extension in 7 patients at varying time points after stroke, in a cross-sectional design. Upper limb function was also measured in all patients. Five of the patients took part in a training program and were measured again, behaviorally and with fMRI posttraining. Healthy control individuals of comparable age were also studied. Results. In patients, reduced activity over time after stroke was found for the group in the supplementary motor area (SMA), contralateral primary motor cortex, and prefrontal and parietal association areas along with ipsilateral cerebellum. Activity in most of these areas was also reduced in the patient group as compared to the control group. After a half-hour of daily training for 4 weeks with repetitive passive and active arm movements, cerebral activation increased in the pre-SMA and SMA, ipsilateral primary sensory cortex and intraparietal sulcus, and contralateral cerebellum in parallel with functional improvements of the upper limb. Areas common to both analyses included the SMA, pre-SMA, primary sensory cortex, intraparietal sulcus, and cerebellum. Conclusions. Our findings suggest that a down-regulation of sensorimotor activity occurs progressively over time as a result of inactivity and that training may reverse the reduced brain activity.

Cortical Activity in Relation to Velocity Dependent Movement Resistance in the Flexor Muscles of the Hand After Stroke

Background. The role of spinal networks in spasticity is well investigated, but little is known about possible cortical contributions to hypertonicity across a joint. Objective. The authors hypothesized that there are cortical activation correlates to spasticity in stroke patients with increased muscle tone of the wrist flexors. Methods. Stroke patients and controls were scanned using event-related functional magnetic resonance imaging (fMRI) during slow and fast passive movements of the hand with simultaneous recording of passive movement resistance (PMR). Results. Control participants had velocity-dependent activity (greater for slow than fast movements) of 2 types, in areas that were also more active in passive movement than rest (eg, relative increase in activation in contralateral S1 and M1 was greater for slow than fast) and in areas that were also more active in rest than passive movement (eg, relative decrease in activation in occipital areas and ipsilateral precentral gyrus was greater for fast than slow). In the patient group, with large interindividual variation of spasticity, we found an association between PMR and the velocity-dependent activity in ipsilateral S1 (area 3b) extending into M1 (area 4a), contralateral cingulate cortex, supplementary motor area (SMA), Brodmann Area 45 (BA 45), and cerebellum. Post hoc testing also revealed a similar correlation in S1 and M1 bilaterally in controls and showed that patients activated ipsilateral S1 and M1 more than controls in the velocity-dependent condition. Conclusions. The findings suggest the possibility of ipsilateral sensory and motor cortical involvement in spasticity after stroke, which warrant further investigation.

Test-retest and inter-rater reliability of a method to measure wrist and finger spasticity.

OBJECTIVE To describe the reliability of an instrument (Neuro- Flexor) designed to be used in the clinic for quantification of the relative contribution of spasticity, elasticity and viscosity to resistance during passive wrist movements. DESIGN A test-retest and inter-rater reliability study. SUBJECTS A convenience sample of 34 adults with chronic stroke with spasticity in the hand, and a reference group of 10 healthy persons. METHODS Two raters assessed the participants with the NeuroFlexor. Elastic, viscous and neural components of passive movement resistance were quantified at the wrist. Test-retest and inter-rater intraclass correlation coefficient (ICC2.1) were calculated for each component for both raters and two sessions. Degree of measurement error was evaluated using the coefficient of variation and the repeatability coefficient. RESULTS Reliability was high for the neural component (test-retest: 0.90-0.96; inter-rater: 0.90-0.94), fair to good for the elastic component (test-retest: 0.79-0.88; inter-rater: 0.76-0.76), and fair to high for the viscous component (test-retest: 0.88-0.90; inter-rater: 0.75-0.80). Based on test-retest data, the coefficients of variation for the neural, elastic and viscous components were 25%, 26% and 16%, respectively, and the repeatability coefficients were 1.798, 1.897 and 1.404, respectively. CONCLUSION The NeuroFlexor instrument is a reliable measure of spasticity and of muscle elasticity and viscosity in individuals with wrist and finger muscle resistance to passive stretch after stroke.

SeNSitivity of the NeurofLexor method to meASure ChANge iN SpAStiCity After treA tmeNt with botuLiNum toxiN A iN wriSt ANd fiNger muSCLeS

OBJECTIVE The NeuroFlexor objectively quantifies the neural, elastic and viscous components of passive movement resistance in wrist and finger flexor muscles. In this study we investigated the sensitivity of the NeuroFlexor to changes in spasticity induced by treatment with botulinum toxin type A (BoNT-A). DESIGN Prospective observational design. SUBJECTS A convenience sample of 22 adults with post-stroke upper limb spasticity scheduled for botulinum toxin treatment. METHODS BoNT-A was given according to individual treatment plans. NeuroFlexor assessments were made before treatment and 4 and 12 weeks after. RESULTS At group level, spasticity decreased significantly at 4 weeks (expected time of maximum effect) (p = 0.04). At 12 weeks, spasticity had rebounded and no longer differed significantly from baseline (p = 0.64), i.e. in line with the pharmacodynamics of BoNT-A. At the individual level, 7 participants showed a reduction in spasticity greater than the measurement error. The reduction was dose-dependent (r(20) = 0.66, p < 0.001), and largest in participants with the highest dose. CONCLUSION At the group level, the sensitivity of NeuroFlexor is good enough to detect reduction in spasticity after treatment with BoNT-A. Further work is needed to establish the sensitivity of NeuroFlexor on an individual level.

Transcranial direct current stimulation combined with visuo-motor training as treatment for chronic stroke patients

BACKGROUND Recent studies exploring the combined effect of motor learning and transcranial direct current stimulation (tDCS) for stroke rehabilitation have shown partially conflicting results. OBJECTIVE To test the efficacy of an optimized hand training approach combined with tDCS in stroke patients. METHODS In the present pilot study we investigated motor effects of four-week training with a visuomotor grip force tracking task combined with tDCS in 11 chronic stroke patients. Anodal (0.5 mA) or sham tDCS was applied over the primary motor cortex of the lesioned side for 20 minutes, twice a day, during training. RESULTS No difference between the Active and Sham groups in the total upper extremity (UE) Fugl-Meyer Assessment (FMA) score was found. The most prominent recovery occurred in the shoulder-elbow FMA sub-score; in this segment a significantly greater improvement in the Active compared to the Sham group was observed up to two months after the intervention. Mean hold force during the first treatment session predicted the change in the total UE FMA score after treatment. CONCLUSION Four-week visuo-motor training combined with tDCS showed no difference between the Active and Sham groups in the total UE FMA score, which may be explained by heterogeneity of the degree of recovery in the Active group. However, the shoulder-elbow FMA sub-score improved significantly more in the Active compared to the Sham group, which deserves further study.