Different Effects of Transcranial Direct Current Stimulation on Leg Muscle Glucose Uptake Asymmetry in Two Women with Multiple Sclerosis

Abstract

Asymmetrical lower limb strength is a significant contributor to impaired walking abilities in people with multiple sclerosis (PwMS). Transcranial direct current stimulation (tDCS) may be an effective technique to enhance cortical excitability and increase neural drive to more-affected lower limbs. A sham-controlled, randomized, cross-over design was employed. Two women with MS underwent two 20 min sessions of either 3 mA tDCS or Sham before 20 min of treadmill walking at a self-selected speed. During walking, the participants were injected with the glucose analogue, [18F] fluorodeoxyglucose (FDG). Participants were then imaged to examine glucose metabolism and uptake asymmetries in the legs. Standardized uptake values (SUVs) were compared between the legs and asymmetry indices were calculated. Subject 2 was considered physically active (self-reported participating in at least 30 min of moderate-intensity physical activity on at least three days of the week for the last three months), while Subject 1 was physically inactive. In Subject 1, there was a decrease in SUVs at the left knee flexors, left upper leg, left and right plantar flexors, and left and right lower legs and SUVs in the knee extensors and dorsiflexors were considered symmetric after tDCS compared to Sham. Subject 2 showed an increase in SUVs at the left and right upper legs, right plantar flexors, and right lower leg with no muscle group changing asymmetry status. This study demonstrates that tDCS may increase neural drive to leg muscles and decrease glucose uptake during walking in PwMS with low physical activity levels.

Post-COVID-19 Fatigue: Potential Contributing Factors

“…At this time, several methods are available to measure many of the contributing factors. Central factors can be studied via neuroimaging procedures such as FDG-PET to measure changes in glucose metabolism [ 50 , 51 ], psychological factors with neuropsychological tests [ 52 ], and peripheral factors can be evaluated by comparing alterations in the electromyography signal with maximal force or power output [ 53 , 54 , 55 ].…”

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

“…Moreover, SUV asymmetry indices (AIs) were calculated to determine the magnitude of asymmetry between the more-and less-affected legs with a previously used equation: ((less-affected side − more-affected side)/((0.5) × (less-affected side + moreaffected side)) × 100). An AI value ≥ 10% was considered asymmetric [32,57,58]. The relative distribution ((standard deviation / mean) × 100) of GU values in PET image voxels within each muscular ROI was calculated as an index of spatial glucose uptake heterogeneity (GUh) [27,28].…”

“…The inclusion and exclusion criteria utilized for this protocol are identical to a previous case report from this lab [32]; a brief description is provided here. The subjects were included if they were between 18-70 years of age, had a positive relapsing-remitting MS diagnosis from a neurologist in accordance with the 2017 revised McDonald's criteria [33], self-reported leg-strength asymmetry, and were able to walk for 20 continuous minutes.…”

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

“…One potential modality to increase cortical excitability and improve motor function in PwMS is transcranial direct current stimulation (tDCS; Jeffery et al, 2007 ; Angius et al, 2016 ). tDCS is a non-invasive means of increasing neuronal excitability of regions under the anode ( Nitsche and Paulus, 2000 ) and has been successfully used in healthy populations ( Workman et al, 2019a , 2020a , b ) and patients with neurological disorders like MS and Parkinson’s disease (PD; Fietsam et al, 2020 ; Workman et al, 2020c ). Increasing the excitability of relevant brain regions might improve motor and cognitive function.…”