Portable neuroimaging and biped multi-task battery to study the effects of non-invasive cerebellar stimulation: a case series on hemiplegic patients with and without basal ganglia lesion

Introduction: The cerebello-thalamo-cortical(CTC) pathway plays a crucial role in postural control and balance. CTC pathway can be facilitated with cerebellar transcranial Direct Current Stimulation(ctDCS) while cortical responses can be measured with portable neuroimaging[1] that was investigated on stroke survivors with and without basal ganglia infarction. Methods: Twelve stroke survivors participated in a single-blind randomized-order crossover study on bipolar ctDCS targeting bilateral dentate nuclei and motor region of cerebellum(details in [1]). Current study investigated two subjects with basal ganglia(BG) lesions based on ctDCS effects on their performance during multi-task battery of overground/treadmill walking, standing weight-shifting(virtual reality-based balance training(VBaT)[2]) as-well-as brain activation at prefrontal cortex(PFC) and sensorimotor cortex(SMC) based on functional near-infrared spectroscopy(fNIRS) and electroencephalogram(EEG). Results: VBaT system identified directional weight-shifting dysfunction(measured by irregularity/sway in center of pressure trajectory) and dynamic variability(measured by coefficient of variation of step time and stride time characterizing walking). The ctDCS intervention did not affect performance in BG-lesion cases(when compared to others[1]). BG-lesioned cases did not fit general linear model well that putatively associated lobular electric field strength with changes in fNIRS-EEG measures at ipsilesional and contra-lesional PFC and SMC[1]. Furthermore, post-ctDCS cerebrovascular reactivity to ctDCS[3] was not significant in BG-lesioned cases while they were significantly(p<0.05) different between the hemispheres in other subjects. Conclusion: Deterioration in biped multi-task performance is postulated to be related to reduced error-correction ability because of BG infarction. Here, cerebrovascular reactivity to ctDCS[3] is postulated to identify responders where BG infarction may affected cerebello-cortical pathway[4] that needs investigation in a larger cohort.