Treatment-Induced Cortical Reorganization After Stroke in Humans

Abstract

Background and Purpose-Injury-induced cortical reorganization is a widely recognized phenomenon. In contrast, there is almost no information on treatment-induced plastic changes in the human brain. The aim of the present study was to evaluate reorganization in the motor cortex of stroke patients that was induced with an efficacious rehabilitation treatment. Methods-We used focal transcranial magnetic stimulation to map the cortical motor output area of a hand muscle on both sides in 13 stroke patients in the chronic stage of their illness before and after a 12-day-period of constraint-induced movement therapy. Results-Before treatment, the cortical representation area of the affected hand muscle was significantly smaller than the contralateral side. After treatment, the muscle output area size in the affected hemisphere was significantly enlarged, corresponding to a greatly improved motor performance of the paretic limb. Shifts of the center of the output map in the affected hemisphere suggested the recruitment of adjacent brain areas. In follow-up examinations up to 6 months after treatment, motor performance remained at a high level, whereas the cortical area sizes in the 2 hemispheres became almost identical, representing a return of the balance of excitability between the 2 hemispheres toward a normal condition. Conclusions-This is the first demonstration in humans of a long-term alteration in brain function associated with a therapy-induced improvement in the rehabilitation of movement after neurological injury. Key Words: plasticity, neuronal Ⅲ transcranial magnetic stimulation Ⅲ reorganization Ⅲ physical therapy Ⅲ stroke R esearch with animals has led to the discovery that cortical reorganization occurs after injury to the nervous system. 1-3 Spontaneously occurring cortical reorganization phenomena that result from nervous system damage or conditions that involve abnormal sensory input have been shown to be associated with pathological states in humans; these include phantom limb pain, 4 tinnitus, 5 and focal hand dystonia. 6 After motor stroke, a complex pattern of reorganization has been described. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] In the subacute stage after a stroke, a reduction in motor cortex excitability and a decrease in the cortical representation area of paretic muscles have been found to occur. 17,19 This may represent a disadvantageous reorganization associated with an impaired motor function and could be due to the damage of neuronal structures or could reflect the disuse of the affected limb. 21,22 In addition to injury-related cortical reorganization, there is a second kind of process, use-dependent cortical reorganization, that results from the increased use of body parts in behaviorally relevant tasks and leads to an enhancement of the representation of those body parts in the cerebral cortex. 21,[23][24][25][26] It is possible that this process could be used to remediate pathological symptoms through the reversal or elimination of disadvantageous cortical reorganizat...

Early Poststroke Experience Differentially Alters Periinfarct Layer II and III Cortex

“…16,26 Similar motor map expansions have been detected in stroke patients treated with constraint-induced movement therapy, where use of the impaired arm and hand is encouraged by limiting use of the non-affected limb. 27 Notably, these studies assessed cortical reorganization long after rehabilitation had commenced and thus it remains unclear whether behavioral recovery coincides temporally with the formation of new somatosensory maps. Interestingly, we previously showed that ischemic rats exposed to ER begin to exhibit enhanced functional recovery as early as 14 days after onset of ER, 3 temporally corresponding with our current findings of increased neuronal activation in periinfarct cortex after 10 days.…”

Robot-assisted movement training compared with conventional therapy techniques for the rehabilitation of upper-limb motor function after stroke

“…16 Nevertheless, this result should be viewed with caution, especially because the robot group did not show improvements in the proximal Fugl-Meyer test over this same 6-month period, and the FIM instrument does not penalize subjects who perform activities using compensation with the less affected limb. Future studies should consider the Motor Activity Log, [5][6][7][8][9] which assesses the actual amount of use of the more affected limb in ADLs and the quality of movement. It would also have been useful to determine if the group differences at the 6-month point were retained 1 year after the treatment.…”

“…[5][6][7] This therapy involves intensive repetitive exercise of the more affected limb coupled with constraint of the opposite limb and results in positive cortical reorganization in the motor cortex. 8 In less severely impaired stroke subjects, simple repetitive exercise may be superior to other types of therapy. CIT has recently been shown to have advantages relative to neurodevelopmental treatment of equal intensity.…”

Task-oriented and Purposeful Robot-Assisted Therapy

“…These results were also verified by Wisneski andJohnson 2006, 2007) for complex ADLs such as drinking and eating. Successful examples of novel task-oriented therapy are forced-use and Constrained-Induced Movement Therapy (CIMT) (Taub et al 1994;Taub et al 1999;Sterr et al 2000;Liepert et al 2002;Page et al 2004;Aycock et al 2004). The training is intense and repetitive, requiring the use of the impaired arm.…”

“…The training is intense and repetitive, requiring the use of the impaired arm. Data indicate that CIMT therapies reduce learned non-use, increase ADL function, and often increase the size and change the location of the cortical area representative of a muscle function (Liepert et al 2002). These forced-use therapies often induce changes in the motor areas especially in the motor cortex and the cerebellum.…”