Alterations in Leg Muscle Glucose Uptake and Inter-Limb Asymmetry after a Single Session of tDCS in Four People with Multiple Sclerosis

Abstract

Asymmetrical lower limb weakness is an early symptom and significant contributor to the progressive worsening of walking ability in people with multiple sclerosis (PwMS). Transcranial direct current stimulation (tDCS) may effectively increase neural drive to the more-affected lower limb and, therefore, increase symmetrical activation. Four PwMS (1 female, age range: 27–57) underwent one session each of 3 mA or SHAM tDCS over the motor cortex corresponding to their more-affected limb followed by 20 min of treadmill walking at a self-selected speed. Two min into the treadmill task, the subjects were injected with the glucose analog [18F]fluorodeoxyglucose (FDG). Immediately after treadmill walking, the subjects underwent whole-body positron emission tomography (PET) imaging. Glucose uptake (GU) values were compared between the legs, the spatial distribution of FDG was assessed to estimate glucose uptake heterogeneity (GUh), and GU asymmetry indices (AIs) were calculated. After tDCS, GU was altered, and GUh was decreased in various muscle groups in each subject. Additionally, AIs went from asymmetric to symmetric after tDCS in the subjects that demonstrated asymmetrical glucose uptake during SHAM. These results indicate that tDCS improved GU asymmetries, potentially from an increased neural drive and a more efficient muscle activation strategy of the lower limb in PwMS.

Effects of bilateral dorsolateral prefrontal cortex high-definition transcranial direct-current stimulation on time-trial performance in cyclists with type 1 diabetes mellitus

“…In particular, tDCS promoted glucose tolerance during a standardized euglycemic-hyperinsulinemic clamp in 15 healthy male volunteers, possibly due to the activation of hypothalamic K ATP channels by transient ATP depletion [17]. In another study, glucose uptake heterogeneity was ameliorated in patients with multiple sclerosis, supposedly through an increased neural drive and a more efficient muscle activation [18].…”

Effects of Transcranial Direct Current Stimulation Over the Left Primary Motor Cortex on Verbal Intelligence

“…Finally, although the current study was conducted in a randomized, double-blinded way with a sham group recruited to mitigate the potential placebo effect, which has been widely implemented in previous tDCS studies ( Giustolisi et al, 2018 ; Rivera-Urbina et al, 2019 ; Mondino et al, 2020 ), it may still be insufficient to rule out all of confounding factors, as sham treatment may inevitably induce sensation different from active conditions ( Fietsam et al, 2021 ) and cause some mild physiological effects that are easily overlooked ( Nikolin et al, 2018 ). Thus, using multi-electrode montages and adding an active control group targeting the brain area that irrelevant to certain tasks may be optional ways to address this issue in the future ( Fonteneau et al, 2019 ).…”

On the Effects of Transcranial Direct Current Stimulation on Cerebral Glucose Uptake During Walking: A Report of Three Patients With Multiple Sclerosis

“…This study employed a single-blind, SHAM-controlled, cross-over design. The subjects attended three sessions with ≥3 days between Sessions 1 and 2 (to allow adequate leg muscle recovery from the isokinetic strength test, detailed below) and ≥7 days between Sessions 2 and 3 to ensure the effects of tDCS were sufficiently diminished ( Nitsche and Paulus, 2000 ; Fietsam et al, 2020 , 2021 ; Figure 1 ). During Session 1, the subjects provided informed consent and completed the Patient Determined Disease Scale (PDDS) and Fatigue Severity Scale (FSS).…”

“…SHAM stimulation produces similar sensations as active tDCS and is used to maintain condition blinding without altering cortical excitability ( Woods et al, 2016 ). These tDCS parameters have been used previously in our lab ( Fietsam et al, 2020 , 2021 ). Following tDCS, the subjects were asked which condition (3 mA or SHAM) they thought they received and described the sensations felt during the stimulation, rated on a 1–10 Likert scale (1 = “barely perceptible; 10 = “Most I could possibly stand”).…”