Ana R.P. Smorenburg

Reflections on Mirror Therapy A Systematic Review of the Effect of Mirror Visual Feedback on the Brain

Background. Mirror visual feedback (MVF), a phenomenon where movement of one limb is perceived as movement of the other limb, has the capacity to alleviate phantom limb pain or promote motor recovery of the upper limbs after stroke. The tool has received great interest from health professionals; however, a clear understanding of the mechanisms underlying the neural recovery owing to MVF is lacking. Objective. We performed a systematic review to assess the effect of MVF on brain activation during a motor task. Methods. We searched PubMed, CINAHL, and EMBASE databases for neuroimaging studies investigating the effect of MVF on the brain. Key details for each study regarding participants, imaging methods, and results were extracted. Results. The database search yielded 347 article, of which we identified 33 suitable for inclusion. Compared with a control condition, MVF increases neural activity in areas involved with allocation of attention and cognitive control (dorsolateral prefrontal cortex, posterior cingulate cortex, S1 and S2, precuneus). Apart from activation in the superior temporal gyrus and premotor cortex, there is little evidence that MVF activates the mirror neuron system. MVF increases the excitability of the ipsilateral primary motor cortex (M1) that projects to the “untrained” hand/arm. There is also evidence for ipsilateral projections from the contralateral M1 to the untrained/affected hand as a consequence of training with MVF. Conclusion. MVF can exert a strong influence on the motor network, mainly through increased cognitive penetration in action control, though the variance in methodology and the lack of studies that shed light on the functional connectivity between areas still limit insight into the actual underlying mechanisms.

Deficits in upper limb position sense of children with Spastic Hemiparetic Cerebral Palsy are distance-dependent

This study examined the arm position sense in children with Spastic Hemiparetic Cerebral Palsy (SHCP) and typically developing children (TD) by means of a contralateral matching task. This task required participants to match the position of one arm with the position of the other arm for different target distances and from different starting positions. Results showed that children with SHCP exhibited with both arms larger matching errors than the TD group, but only when the distance between the arms at the start of the movement was large. In addition, the difference in errors between the less-impaired and the impaired limb changed as a function of the distance in the SHCP group whereas no interlimb differences were found in the TD group. Finally, spasticity and restricted range of motion in children with SHCP were not related to the proportion of undershoot and size of absolute error. This suggests that SHCP could be associated with sensory problems in conjunction with their motor problems. In conclusion, the current study showed that accurate matching of the arms is greatly impaired in SHCP when compared to TD children, irrespective of which arm is used. Moreover, this deficit is particularly present for large movement amplitudes.

Does Corticospinal Tract Connectivity Influence the Response to Intensive Bimanual Therapy in Children With Unilateral Cerebral Palsy

Background. Reorganization of the corticospinal tract (CST) can occur in unilateral spastic cerebral palsy (USCP). The affected hand can be controlled via (1) typical contralateral projections from the lesioned hemisphere, (2) ipsilateral projections from the nonlesioned hemisphere, and (3) a combination of contralateral and ipsilateral projections (ie, bilateral). Intensive bimanual therapy and constraint-induced movement therapy (CIMT) improve hand function of children with USCP. Earlier it was suggested that the CST connectivity pattern may influence the efficacy of CIMT. Objective. To examine whether CST projection pattern influences the efficacy of intensive bimanual therapy in children with USCP. Participants. Thirty-three children with USCP (age 8.9 ± 2.6 years, 16 females). Methods. Bimanual therapy was provided in a day-camp setting (90 hours). Participants were involved in different bimanual play and functional activities actively engaging both hands. Hand function was tested before and after the intervention with the Jebsen-Taylor Test of Hand Function, Assisting Hand Assessment, ABILHAND-Kids, and the Canadian Occupational Performance Measure. Single-pulse transcranial magnetic stimulation (TMS) was used to determine each child’s CST projection pattern (ie, ipsilateral, contralateral, or bilateral). Results. Children whose affected hand was controlled only by ipsilateral CST projections had worse Jebsen-Taylor Test of Hand Function and Assisting Hand Assessment scores than children in the contralateral group at baseline. Bimanual hand use and functional hand use was independent of CST projection pattern. After bimanual therapy, improvements on all outcome measures were observed, and these improvements were independent of the CST connectivity pattern. Conclusion. The efficacy of bimanual therapy on hand function in children with USCP appears to be independent of CST connectivity pattern.

Visual feedback of the non-moving limb improves active joint-position sense of the impaired limb in Spastic Hemiparetic Cerebral Palsy

This study examined the active joint-position sense in children with Spastic Hemiparetic Cerebral Palsy (SHCP) and the effect of static visual feedback and static mirror visual feedback, of the non-moving limb, on the joint-position sense. Participants were asked to match the position of one upper limb with that of the contralateral limb. The task was performed in three visual conditions: without visual feedback (no vision); with visual feedback of the non-moving limb (screen); and with visual feedback of the non-moving limb and its mirror reflection (mirror). In addition to the proprioceptive measure, a functional test [Quality of Upper Extremity Skills Test (QUEST)] was performed and the amount of spasticity was determined in order to examine their relation with proprioceptive ability. The accuracy of matching was significantly influenced by the distance that had to be covered by the matching limb; a larger distance resulted in a lower matching accuracy. Moreover it was demonstrated that static (mirror) visual feedback improved the matching accuracy. A clear relation between functionality, as measured by the QUEST, and active joint-position sense was not found. This might be explained by the availability of visual information during the performance of the QUEST. It is concluded that static visual feedback improves matching accuracy in children with SHCP and that the initial distance between the limbs is an influential factor which has to be taken into account when measuring joint-position sense.

Practicing a matching movement with a mirror in individuals with spastic hemiplegia.

This experimental study aimed to determine the effect of practicing a position matching task with (mirror) visual feedback of the less-impaired arm on the matching accuracy of the impaired arm in children and adolescents with spastic hemiparetic cerebral palsy. Practice consisted of 40 trials of bimanual target matching, where one group received regular visual feedback and a second group received mirror visual feedback of the less-impaired arm. On three occasions (pre, post, and after a 1-week-retention) position sense (matching accuracy measured as the endpoint error in cm) of the impaired arm was tested with a unimanual and bimanual matching task, performed without any visual information of either hand. Matching accuracy of the impaired arm was better in the post-test than in the pre-test, but this improvement was similar for both practice groups. In the retention-test, accuracy had returned to pre-test-level, which might be ascribed to the short duration of the practice period. These outcomes suggest that practicing a matching task with visual feedback of the less-impaired arm might help to improve the matching accuracy of the impaired arm in individuals with spastic hemiparetic cerebral palsy.

The positive effect of mirror visual feedback on arm control in children with spastic hemiparetic cerebral palsy is dependent on which arm is viewed.

Mirror visual feedback has previously been found to reduce disproportionate interlimb variability and neuromuscular activity in the arm muscles in children with Spastic Hemiparetic Cerebral Palsy (SHCP). The aim of the current study was to determine whether these positive effects are generated by the mirror per se (i.e. the illusory perception of two symmetrically moving limbs, irrespective of which arm generates the mirror visual feedback) or by the visual illusion that the impaired arm has been substituted and appears to move with less jerk and in synchrony with the less-impaired arm (i.e. by mirror visual feedback of the less-impaired arm only). Therefore, we compared the effect of mirror visual feedback from the impaired and the less-impaired upper limb on the bimanual coupling and neuromuscular activity during a bimanual coordination task. Children with SHCP were asked to perform a bimanual symmetrical circular movement in three different visual feedback conditions (i.e. viewing the two arms, viewing only one arm, and viewing one arm and its mirror image), combined with two head orientation conditions (i.e. looking from the impaired and looking from the less-impaired body side). It was found that mirror visual feedback resulted in a reduction in the eccentric activity of the Biceps Brachii Brevis in the impaired limb compared to the condition with actual visual feedback from the two arms. More specifically, this effect was exclusive to mirror visual feedback from the less-impaired arm and absent when mirror visual feedback from the impaired arm was provided. Across conditions, the less-impaired arm was the leading limb, and the nature of this coupling was independent from visual condition or head orientation. Also, mirror visual feedback did not affect the intensity of the mean neuromuscular activity or the muscle activity of the Triceps Brachii Longus. It was concluded that the positive effects of mirror visual feedback in children with SHCP are not just the result of the perception of two symmetrically moving limbs. Instead, in order to induce a decrease in eccentric neuromuscular activity in the impaired limb, mirror visual feedback from the ‘unaffected’ less-impaired limb is required.

Matching accuracy in hemiparetic cerebral palsy during unimanual and bimanual movements with (mirror) visual feedback

In the present study participants with Spastic Hemiparetic Cerebral Palsy (SHCP) were asked to match the position of a target either with the impaired arm only (unimanual condition) or with both arms at the same time (bimanual condition). The target was placed at 4 different locations scaled to the individual maximum reaching distance. To test the effect of mirror visual feedback of the less-impaired arm on the matching accuracy, an opaque screen or a mirror was placed in between the arms which masked vision of the impaired arm. Absolute endpoint error was smaller in the bimanual condition compared to the unimanual condition, but there was no effect of mirror visual feedback. Inspection of the individual data, however, showed that 13 out of 23 participants did experience a positive effect of mirror visual feedback. A positive correlation between the baseline error (screen) and the improvement in accuracy with mirror visual feedback seems to suggest that individuals with lower proprioceptive accuracy in the baseline condition may benefit more from mirror visual feedback. Together these findings indicate that bimanual therapy and therapy with mirror visual feedback might be valuable approaches for rehabilitation for a subset of the individuals with SHCP.

The Relationship Between Hand Function and Overlapping Motor Representations of the Hands in the Contralesional Hemisphere in Unilateral Spastic Cerebral Palsy

Background. In many children with unilateral spastic cerebral palsy (USCP), the corticospinal tract to the affected hand atypically originates in the hemisphere ipsilateral to the affected hand. Such ipsilateral connectivity is on average a predictor of poor hand function. However, there is high variability in hand function in these children, which might be explained by the complexity of motor representations of both hands in the contralesional hemisphere. Objective. To measure the link between hand function and the size and excitability of motor representations of both hands, and their overlap, in the contralesional hemisphere of children with USCP. Methods. We used single-pulse transcranial magnetic stimulation to measure the size and excitability of motor representations of both hands, and their overlap, in the contralesional hemisphere of 50 children with USCP. We correlated these measures with manual dexterity of the affected hand, bimanual performance, and mirror movement strength. Results. The main and novel findings were (1) the large overlap in contralesional motor representations of the 2 hands and (2) the moderate positive associations of the size and excitability of such shared-site representations with hand function. Such functional associations were not present for overall size and excitability of representations of the affected hand. Conclusions. Greater relative overlap of the affected hand representation with the less-affected hand representation within the contralesional hemisphere was associated with better hand function. This association suggests that overlapping representations might be adaptively “yoked,” such that cortical control of the child’s less-affected hand supports that of the affected hand.

Quantification of functional abilities in Rett syndrome: a comparison between stages III and IV

We aimed to evaluate the functional abilities of persons with Rett syndrome (RTT) in stages III and IV. The group consisted of 60 females who had been diagnosed with RTT: 38 in stage III, mean age (years) of 9.14, with a standard deviation of 5.84 (minimum 2.2/maximum 26.4); and 22 in stage IV, mean age of 12.45, with a standard deviation of 6.17 (minimum 5.3/maximum 26.9). The evaluation was made using the Pediatric Evaluation of Disability Inventory, which has 197 items in the areas of self-care, mobility, and social function. The results showed that in the area of self-care, stage III and stage IV RTT persons had a level of 24.12 and 18.36 (P=0.002), respectively. In the area of mobility, stage III had 37.22 and stage IV had 14.64 (P<0.001), while in the area of social function, stage III had 17.72 and stage IV had 12.14 (P=0.016). In conclusion, although persons with stage III RTT have better functional abilities when compared with stage IV, the areas of mobility, self-care, and social function are quite affected, which shows a great functional dependency and need for help in basic activities of daily life.

Gaze Behaviour during Interception in Children with Spastic Unilateral Cerebral Palsy.

Anticipatory gaze behaviour during interceptive movements was investigated in children with Spastic Unilateral Cerebral Palsy (SUCP), and related to the side of the intracerebral lesion. Five children with lesions of the right hemisphere (RHL) and five children with lesions of the left hemisphere (LHL) had to walk towards and intercept a ball that moved perpendicular to the walking path. Interception accuracy and gaze patterns were measured in a no-occlusion and occlusion condition, in which the ball was occluded from view for half of its trajectory. There was a clear support for a relationship between gaze behaviour and success in interception performance, with some evidence for the presence of anticipatory gaze behaviour. There were also differences in gaze behaviour between children with RHL and children with LHL that might be related to planning, but these did not affect interception accuracy. It is concluded that gaze behaviour during interceptive movements is anticipatory, and at least partly dependent on the lesional side.