Transcranial direct current stimulation with sensory modulation intervention (tDCS-SM): Treatment effects and underlining mechanisms in patients with severe to moderate upper extremity paresis after stroke
Date Issued
2016
Date
2016
Author(s)
Koh, Chia-Lin
Abstract
Backgroud and purposes Up to 60% of people with stroke suffered from severe to moderate long-term upper extremity（UE）motor impairment. The deficits of UE can greatly impact patients‘ daily living independence and quality of life. However, treatment effect of current interventions is still limited. Nick Ward and Leonardo Cohen suggested 5 intervention strategies for stroke motor recovery:（1）reduction of somatosensory input from the intact;（2）increase in somatosensory input from the paretic;（3）anesthesia of a body part proximal to the paretic hand;（4）activity within the affected motor cortex may be up-regulated;（5）activity within the intact motor cortex may be down-regulated. Recent studies have shown each strategy to be effective in stroke patients with mild or moderate UE impairment. However, evidence for people with severe UE impairment after stroke remains unclear. Since research has found a greater effect for combined strategies than a single strategy, this proposal develops a combined intervention with the above 5 strategies, named Transcranial direct current stimulation with sensory modulation intervention (tDCS-SM). tDCS-SM is expected to be most effective for people with severe UE impairment after stroke. In addition, neuroimaging can provide in vivo information about the brain plasticity which underpinning the motor recovery after stroke. However, image indexes that can be used in stroke patients with severe UE impairment remained examined. Therefore, this study aimed to examined whether a multi-strategy intervention (i.e., tDCS-SM) enhanced motor outcome immediately and longitudinally in patients with chronic severe to moderate upper extremity paresis. In addition, the underline mechanism of the tDCS-SM’s efficacy was examined using neuroimaging technology. Methods A total of 25 stroke participants were randomly assigned to either a transcranial direct current stimulation with sensory modulation (tDCS-SM) group or a control group for an 8-week intervention. The tDCS-SM group (n = 14) received bilateral tDCS stimulation, bilateral cutaneous anesthesia, and high repetitions of passive movements on the paretic hand. The control group (n = 11) received the same repetitive passive motor training but with sham tDCS and sham anesthesia. Outcomes were assessed at baseline, at post-intervention, and at 3- and 6-month follow-ups. All enrolled participants who were diagnosed as ischemic stroke received diffusion spectrum and functional magnetic resonance imaging at 3T. Corticospinal tract (CST) and callosal motor fiber (CMF) integrity was assessed by measuring the mean generalized fractional anisotropy (mGFA) of the reconstructed tracts. The CST tractogram was segmented from the internal capsule to the motor cortex (CSTABOVE) and the internal capsule parts only (CSTPLIC). The CMF tractogram was segmented from the mid-sagittal plane to the motor cortex. For the functional magnetic resonance imaging, all participants received passive finger extension movemnt during scanning. Data were analyzed with SPM99. Results The Fugl-Meyer motor score improved more in the tDCS-SM group than in the control group, with a moderate between-group effect size (partial η2, ηp2 = 0.14), and long-term effects of tDCS-SM were found (ηp2 =0.17 and 0.12). The tDCS-SM group exhibited a slightly better immediate effect (ηp2 = 0.02 – 0.04) on reducing spasticity than the control group, but no long-term effect. Small immediate and long-term treatment effects of tDCS-SM were found on hand function and daily function recovery (ηp2 = 0.02 - 0.09). No difference between groups was found for the lateraliry index and the mGFA of CSTABOVE. Significant differences between groups were found for the mGFA and the laterality index of the unaffected CSTPLIC. The control group showed a large decrease of mGFA at the unaffected CSTPLIC. The CMF integrity was not compared due to limited no sufficient case number in the control group. Conclusion tDCS-SM showed better immediate and long-term effects on voluntary UE movement recovery than intensive passive movement intervention. The effects of tDCS-SM on spasticity control and functional changes were found in the short term but not in the long term in patients with severe to moderate UE paresis. For ischemic stroke, the tDCS-SM maintained the unaffected CST structural integrity from being degenerated. The results of this study suggested that the tDCS-SM has potential to improve UE motor recovery in patients with severe to moderate UE paresis, however, the treatment effects of tDCS-SM to improve patients‘ functional recovery were still limited.
Subjects
stroke
upper extremity
brain stimulation
passive motor training
recovery mechanism
Type
thesis
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