Sung Ho Jang

Repetitive Transcranial Magnetic Stimulation–Induced Corticomotor Excitability and Associated Motor Skill Acquisition in Chronic Stroke

Background and Purpose— Although there is some early evidence showing the value of repetitive transcranial magnetic stimulation (rTMS) in stroke rehabilitation, the therapeutic effect of high-frequency rTMS, along with the physiology of rTMS-induced corticomotor excitability supporting motor learning in stroke, has not been established. This study investigated high-frequency rTMS-induced cortical excitability and the associated motor skill acquisition in chronic stroke patients. Methods— Fifteen patients with chronic hemiparetic stroke (13 men; mean age 53.5 years) practiced a complex, sequential finger motor task using their paretic fingers either after 10 Hz or sham rTMS over the contralateral primary motor cortex (M1). Both the changes in the behavior and corticomotor excitability before and after the intervention were examined by measuring the movement accuracy, the movement time, and the motor-evoked potential (MEP) amplitude. A separate repeated-measures ANOVA and correlation statistics were used to determine the main and interaction effects as well as relationship between the changes in the behavioral and corticomotor excitability. Results— High-frequency rTMS resulted in a significantly larger increase in the MEP amplitude than the sham rTMS (P<0.01), and the plastic change was positively associated with an enhanced motor performance accuracy (P<0.05). Conclusions— High-frequency rTMS of the affected motor cortex can facilitate practice-dependent plasticity and improve the motor learning performance in chronic stroke victims.

Virtual Reality–Induced Cortical Reorganization and Associated Locomotor Recovery in Chronic Stroke An Experimenter-Blind Randomized Study

Background and Purpose— Virtual reality (VR) is a new promising computer-assisted technology to promote motor recovery in stroke patients. VR-induced neuroplasticity supporting locomotor recovery is not known. We investigated the effects of VR intervention on cortical reorganization and associated locomotor recovery in stroke patients. Methods— Ten chronic stroke patients were assigned randomly to either the control group or the VR group. VR was designed to provide interactive real-life practice environments in which practice parameters can be individualized to optimize motor relearning. Laterality index (LI) in the regions of interests (ROIs) and locomotor recovery were measured before and after VR using functional MRI (fMRI) and standardized locomotor tests, respectively. The t test and nonparametric test were performed to compare the mean differences at P<0.05. Results— There was a significant difference in the interval change in the LI score for the primary sensorimotor cortex (SMC) between the groups (P<0.05), indicating that VR practice produced a greater increase in LI for the control group. However, the interval changes in the other ROIs were not significantly different (P>0.05). Motor function was significantly improved after VR (P<0.05). Conclusions— Our novel findings suggest that VR could induce cortical reorganization from aberrant ipsilateral to contralateral SMC activation. This enhanced cortical reorganization might play an important role in recovery of locomotor function in patients with chronic stroke. This is the first fMRI study in the literature that provides evidence for neuroplasticity and associated locomotor recovery after VR.

Cortical reorganization induced by virtual reality therapy in a child with hemiparetic cerebral palsy.

Virtual reality (VR) therapy is a new, neurorehabilitation intervention aimed at enhancing motor performance in children with hemiparetic cerebral palsy (CP). This case report investigated the effects of VR therapy on cortical reorganization and associated motor function in an 8‐year‐old male with hemiparetic CP. Cortical activation and associated motor development were measured before and after VR therapy using functional magnetic resonance imaging (fMRI) and standardized motor tests. Before VR therapy, the bilateral primary sensorimotor cortices (SMCs) and ipsilateral supplementary motor area (SMA) were predominantly activated during affected elbow movement. After VR therapy, the altered activations disappeared and the contralateral SMC was activated. This neuroplastic change was associated with enhanced functional motor skills including reaching, self‐feeding, and dressing. These functions were not possible before the intervention. To our knowledge, this is the first fMRI study in the literature that provides evidence for neuroplasticity after VR therapy in a child with hemiparetic CP.

Use of Virtual Reality to Enhance Balance and Ambulation in Chronic Stroke: A Double-Blind, Randomized Controlled Study

Kim JH, Jang SH, Kim CS, Jung JH, You JH: Use of virtual reality to enhance balance and ambulation in chronic stroke: A double-blind, randomized controlled study. Objective: To examine an additive effect of virtual reality on balance and gait function in patients with chronic hemiparetic stroke. Design: Twenty-four adults with hemiparetic stroke were randomly assigned to either an experimental group (n = 12) or a control group. Both groups underwent conventional physical therapy, 40 mins a day, 4 days a week for 4 wks. The experimental group received an additional 30 mins of virtual reality therapy each session. Balance performance was determined by the Balance Performance Monitor and Berg Balance Scale tests. Gait performance was determined by the 10-m walking test and Modified Motor Assessment Scale, and spatiotemporal parameters were obtained using GAITRite. Analysis of variance and correlation statistics were performed at P < 0.05. Results: In the balance test, the experimental group had improved Berg Balance Scale scores, balance and dynamic balance angles (ability to control weight shifting) compared with the controls (P < 0.05). In the gait performance test, the experimental group showed significant improvements in velocity, Modified Motor Assessment Scale scores, cadence, step time, step length, and stride length (P < 0.05). Improvement in dynamic balance angles was correlated with velocity and cadence (P < 0.01). Conclusions: This study demonstrates that virtual reality has an augmented effect on balance and associated locomotor recovery in adults with hemiparetic stroke when added to conventional therapy.

Motor outcome according to the integrity of the corticospinal tract determined by diffusion tensor tractography in the early stage of corona radiata infarct

Diffusion tensor tractography (DTT) is useful for exploring the state of the corticospinal tract (CST). An accurate estimation of the integrity of the CST in the early stage of a cerebral infarct would enable a determination of motor recovery. DTT was performed to classify CST integrity following a corona radiata infarct to evaluate if the procedure could characterize the motor outcome of the affected hand. Fifty-five patients with completely paralyzed hands due to a corona radiata infarct were recruited for the study, and DTT images were obtained within 7-30 days after a stroke. The DTI findings for the patients were classified into four groups. In type A, the CST was preserved around the infarct; in type B, the CST originated from a cortex other than the primary motor cortex; in type C, the CST was interrupted at the infarct; in type D, the CST failed to reach the infarct due to degeneration. Six months after a stroke, the motor function of the affected hand was evaluated with the motricity index (MI) for the hand, the Medical Research Council score (MRC) for finger extensors and the modified Brunnstrom classification (MBC). These indices were significantly influenced by the DTT type (p<0.05). The highest MI, MRC and MBC were seen in the DTT type A patients; the lowest MI, MRC and MBC were seen in the DTT type D patients (p<0.05). The integrity of the corticospinal tract determined by DTT obtained during the early stage of a corona radiata infarct seems to be helpful in predicting the motor outcome of the affected hand.

Motor outcome according to diffusion tensor tractography findings in the early stage of intracerebral hemorrhage

We tried to investigate the motor outcome according to diffusion tensor tractography (DTT) findings for the corticospinal tract (CST) in the early stage for hemiparetic patients with intracerebral hemorrhage (ICH). Forty patients with severe paralysis of the affected side were enrolled. DTT was obtained in the early stage of the stroke (7-30 days) and was classified into four groups: type A, the CST originating from primary motor cortex was preserved around the hematoma; type B, the CST was similar to type A except the fiber originated from the adjacent areas to the primary motor cortex; type C, the CST was interrupted at or around the hematoma; and type D, the CST did not reach the hematoma due to degeneration (Fig. 1). Six months after onset, motor function was measured and the statistical influence of the DTT type was tested. Initially, none of the motor function scales of the affected side differed among the four DTT types. Six months after the onset of ICH, motor functions of the same side were significantly different according to DTT type (p<0.05). All motor scales were highest in the DTT type A group, and were lowest in the DTT type D group (p<0.0003). The early DTT findings for CST may be used to predict the motor outcome of the affected extremities in hemiparetic patients with ICH.

The effect of transcranial direct current stimulation on the cortical activation by motor task in the human brain: An fMRI study

OBJECTIVES We attempted to evaluate whether cortical activation resulting from hand movements is changed by transcranial direct current stimulation (tDCS) applied on the primary motor cortex for the hand in the human brain, using functional MRI (fMRI). METHODS Fourteen normal subjects were recruited; subjects were randomly assigned to either the tDCS group (n=7) or the sham group (n=7). fMRI was performed with hand grasp-release movements at 1Hz before and after 20 min of intervention (the tDCS group: anodal tDCS, the sham group: sham stimulation). RESULTS The activation of the tDCS underlying primary sensorimotor cortex (SM1) was significantly increased in the tDCS group (p<0.05). By contrast, the SM1 was significantly decreased in the sham group in terms of the voxel count and intensity (p<0.05). No subjects complained of any adverse symptoms or signs. CONCLUSION We demonstrated that anodal tDCS increased the cortical excitability of the underlying motor cortex in the human brain. It seems that tDCS is an effective modality to modulate brain function.

Bilateral primary sensori-motor cortex activation of post-stroke mirror movements: an fMRI study

&NA; This fMRI study was undertaken to test whether the pathophysiological mechanism of mirror movements in hemiparetic stroke patients involves activation of the unaffected motor cortex. We studied 16 control subjects and 51 stroke patients. fMRI was performed at 1.5Tusing a finger flexion‐extension movement paradigm. The incidence of bilateral primary sensorimotor cortex activation was significantly increased during movements of the affected hand of stroke patients who showed mirror movements. Moreover, the incidence of bilateral primary sensorimotor cortex activation increased with the severity of mirror movements and primary sensorimotor cortex was activated bilaterally in all patients who showed sustained mirror movements.We conclude that the motor cortex activation on the non‐stroke side is associated with mirror movements and is correlated with the severity of mirror movements. It seems that the pathophysiological mechanism of sustained mirror movements in stroke patients involves the unaffected motor cortex. NeuroReport 14:1329–1332

Functional Role of the Corticoreticular Pathway in Chronic Stroke Patients

Background and Purpose— The corticoreticular pathway (CRP) is known to be an important extrapyramidal tract for walking ability. However, little is known about the functional role of the CRP in recovery of walking ability. We investigated relation between the CRP and walking ability in chronic hemiparetic stroke patients. Methods— Among 209 consecutive patients, 54 patients, who showed complete injury of the corticospinal tract (CST) in the affected hemisphere on diffusion tensor tractography, and 20 normal subjects were recruited. Functional ambulation category was used in measurement of walking ability. The fractional anisotropy value, apparent diffusion coefficient value, and fiber volume of the CRP and CST were used for the diffusion tensor imaging parameters. Results— In the affected hemisphere, no significant difference in diffusion tensor imaging parameters of the CRP was observed between patient subgroups. In the unaffected hemisphere, patients who were able to walk showed significantly increased fiber volume of the CRP, compared with patients who could not walk and normal control subjects (P<0.05), without significant difference in fractional anisotropy and apparent diffusion coefficient values. In addition, the fiber volume of the CRP in the unaffected hemisphere showed positive correlation with functional ambulation category (P<0.05). In contrast, diffusion tensor imaging parameters of the CST in the unaffected hemisphere showed no correlation with functional ambulation category (P>0.05). Conclusions— The increased fiber volume of the CRP in the unaffected hemisphere seems to be related to walking ability in patients with chronic stroke. Therefore, the compensation of the CRP in the unaffected hemisphere seems to be one of the mechanisms for recovery of walking ability after stroke.

Cortical effect and functional recovery by the electromyography-triggered neuromuscular stimulation in chronic stroke patients

We investigated the effect of electromyography (EMG)-triggered neuromuscular electrical stimulation (NMES; EMG-stim) on functional recovery of the hemiparetic hand and the related cortical activation pattern in chronic stroke patients. We enrolled 14 stroke patients, who were randomly assigned to the EMG-stim (n=7) or the control groups (n=7). The EMG-stim was applied to the wrist extensor of the EMG-stim group for two sessions (30 min/session) a day, five times per week for 10 weeks. Four functional tests (box and block, strength, the accuracy index, and the on/offset time of muscle contraction) and functional MRI (fMRI) were performed before and after treatment. fMRI was measured at 1.5 T in parallel with timed finger flexion-extension movements at a fixed rate. Following treatment, the EMG-stim group showed a significant improvement in all functional tests. The main cortical activation change with such functional improvement was shifted from the ipsilateral sensorimotor cortex (SMC) to the contralateral SMC. We demonstrated that 10-week EMG-stim can induce functional recovery and change of cortical activation pattern in the hemiparetic hand of chronic stroke patients.