Anodal tDCS over left parietal cortex expedites recovery from stroke-induced apraxic imitation deficits: a pilot study

Abstract

Background: To date, specific therapeutic approaches to expedite recovery from apraxic deficits after left hemisphere (LH) stroke remain sparse. Thus, in this pilot study we evaluated the effect of anodal transcranial direct current stimulation (tDCS) in addition to a standardized motor training on apraxic imitation deficits. Methods: In a rehabilitation hospital, we assessed apraxic, aphasic, and motor deficits in 30 LH stroke patients before and after a five-day standard programme of motor training combined with either anodal (10 min, 2 mA; n = 14) or sham (10 min, 0 mA, n = 16) tDCS applied in a double-blind fashion over left posterior parietal cortex (PPC). Where appropriate, data were analyzed with either t-test, Fisher's exact test, or univariate/ repeated measures ANOVA. Results: Compared to sham tDCS, five sessions of anodal tDCS expedited recovery from apraxic imitation deficits (p < 0.05): Already after 5 days, the anodal tDCS group showed levels of imitation performance that were achieved in the sham tDCS group after 3 months. However, the primary outcome of the study (i.e., anodal tDCS induced improvement of the total apraxia score) failed significance, and there was no significant tDCS effect on apraxia after 3 months. Anodal tDCS improved grip force (of the contra-lesional, i.e., right hand), but had no effect on aphasia. Conclusions: Data from this pilot study show that repetitive, anodal tDCS over left PPC combined with a standardized motor training expedites recovery from imitation deficits in LH stroke patients with apraxia (relative to sham stimulation). Results suggest that in patients suffering from apraxic imitation deficits a randomized controlled trial (RCT) is warranted that investigates the effects of tDCS applied over PPC in addition to a standardized motor training.

Exploring and optimizing the neuroplastic effects of anodal transcranial direct current stimulation over the primary motor cortex of older humans

“…A considerable number of studies in healthy and pathological aging have shown encouraging results for application of tDCS to counteract age-associated decline in various functional domains [78][79][80][81]. Moreover, tDCS has been suggested to be effective in treating symptoms in patients with brain lesions after stroke [82][83][84][85], or in Parkinson´s disease [85], which often develop in higher age. However, despite promising findings described in these studies, a lack of positive functional effects of tDCS were also reported in older adults [24,25,[86][87][88], which might be due to the application of suboptimal stimulation protocols.…”

Verum versus sham tDCS in the treatment of stroke-induced apraxia: study protocol of the randomized controlled trial RAdiCS -“Rehabilitating (stroke-induced) Apraxia with direct Current Stimulation”

“…We assume that the verum stimulation (anodal tDCS over the left parietal lobe) leads to a more significant improvement in apraxia severity than sham stimulation [ 1 ]. The primary endpoint is the difference in the total score of the Cologne Apraxia Screening (KAS [ 19 ]) between the post-interventional investigation and baseline.…”

“…A pilot study following the identical interventional and training procedure was performed before this RCT [ 1 ]. Here, 20 apraxic patients showed a standard deviation (SD) of about 7 points in the comparison of the KAS-score between baseline and post-interventional assessment.…”

“…However, up to date, due to a lack of (large) randomized controlled trials (RCTs), there is no Level A recommendation (definitive efficacy) for tDCS in post-stroke rehabilitation for any specific indication [ 13 ]. For apraxia, studies in healthy subjects [ 18 ], apraxic stroke patients [ 1 , 5 ], and patients with cortico-basal syndrome [ 3 ] showed an improvement in (hand) gesture processing and imitation by anodal tDCS over the left posterior parietal cortex (PPC).…”

Improved gesturing in left-hemispheric stroke by right inferior parietal theta burst stimulation

“…The effect correlated with measures of transcallosal connectivity in the splenium corporis callosi to the IPL-L pointing to an interhemispheric facilitation of this area. Furthermore, it was shown in stroke patients, that the excitatory stimulation by tDCS of the lesioned posterior parietal cortex improved the performance of gestural imitation (Bolognini et al, 2015;Ant et al, 2019).…”