Rehabilitation Figure 3: Simplified Model of the Imbalance in Interhemispheric Interactions after Stroke and Therapeutic Options
Anodal TDCS
Cathodal TDCS
The inhibitory influence of ipsilesional onto contralesional motor cortex is decreased, which in turn leads to a disinhibition of contralesional motor cortex (left). Non-invasive transcranial direct current stimulation (TDCS) provides two therapeutic options aiming at ‘re-balancing’ this imbalance. Upregulation of excitability of the ipsilesional motor cortex spared by the stroke (middle) and downregulation of excitability of the contralesional motor cortex (right). Source: Schlaug et al., 2008.41
Figure 4: Abnormal Activation Pattern Related to Passive Elbow Movements in Chronic Stroke Patients with Severe Spastic Hemiparesis (A)
A B 1.0
Similarly, mental training was reported to result in better functionality of the upper extremity and in greater gains of activities of daily living than standard physiotherapy.76,77
FMRI revealed 0.0
14 Session
2 C 1.0 3
that motor imagery activated a widespread network of areas in motor, premotor and parietal cortices in both cerebral hemispheres. Similarly, a daily treatment with observing actions combined with physical training for four weeks resulted in a significant increase in motor functions that lasted for at least eight weeks after training.78
This 0.0
14 Session
2 3
Passive elbow movements induced a bilateral activation in sensorimotor cortex. However, movements of the affected arm showed a smaller activation in the ipsilesional hemisphere than movements of the non-affected arm in the contralesional hemisphere. Also, movements of the affected arm showed greater ipsilateral activation than movements of the non-affected arm. Patients with residual movement activity showed an increase of the fMRI-signal in the dorsal portion of the ipsilesional motor cortex following combined botulinum toxin (BTX) and cycling arm training both in relation to passive movements of the affected and non-affected arm (B). In contrast, patients with complete hemiplegia showed a similar training effect only for the affected arm but not for the non-affected arm, which was possibly due to an interhemispheric disconnection resulting from the infarct lesion (c). Source: Diserens et al., 2010.98
treadmill training was found to improve walking velocity, which correlated with brain activity in the posterior cerebellum related to movement of the paretic limb.71
Even passive training of wrist movements was reported to be clinically effective and to change the cortical activation,72
although
evidence from 3D motor analysis showed that successful hand shaping and grasping of objects did not occur when there was not sufficient volitional control of finger and thumb extensions.73
More recently, cognitive training strategies have been promoted in addition to peripheral sensorimotor activities. It has been assumed that the inferior frontal cortex plays a critical role in motor recovery
108
was associated with a significant overactivation compared with the control group in ventral premotor cortices, superior temporal gyri, the supplementary motor area and supramarginal gyrus related to an object manipulation task. However, it must be mentioned that the capacity to perform motor imagery can be weakened by limb loss or disuse, although the temporal characteristics of motor imagery may be not affected.79
Brain Stimulation as an Add-on to Peripheral Sensorimotor Activities
In the context of experimental rehabilitative therapies, the model of interhemispheric imbalance and the important role of transcallosal connections provide a framework for hypotheses based on two facets: upregulating excitability of intact portions of the ipsilesional motor cortex, and downregulating excitability of the contralesional motor cortex. The contralesional cortex is presumed to be disinhibited due to the lack of an inhibitory influence from the lesional motor cortex while at the same time it exerts an unbalanced inhibitory influence on the lesioned motor region. The downregulation of the contralesional, disinhibited motor regions is presumed to counter an abnormal inhibitory influence on ipsilesional regions (see Figure 3).41,53,80
Pilot
studies, using either rapid transcranial magnetic stimulation (rTMS)81–84 or transcranial direct cortical stimulation (tDCS),85–88
have shown that US NEUROLOGY
since there are so-called mirror neurons that become active not only in relation to motor activity but also in response to observation and imagery of the same type of movements. In controlled trials mirror therapy undertaken soon after stroke was found to improve the neurological status immediately after the intervention and at long-term follow-up.74,75
Mean BOLD activity
Mean BOLD activity
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