This study is an exploratory study to see if we can detect changes in fMRI activity during TENS in persons with MS. This is a randomized, single-blind crossover design. Subjects will undergo an MRI scan while they receive sham stimulation of the tibialis anterior, active stimulation of the tibialis anterior, stimulation of the quadriceps, perform continuous movements of the foot (plantar \& dorsiflexion) and a combination of stimulation of the tibialis anterior and movement of the foot. This study will include 15 subjects with relapsing remitting or progressive MS and 15 healthy controls. Blood-oxygen-level-dependent (BOLD) activation changes and the interaction networks before, during and after active TENS and differences in activation due to stimulation on quadriceps vs. tibialis anterior, stimulation on tibialis anterior vs plantar/dorsiflexion and stimulation on tibialis anterior vs stimulation combined with plantar/dorsiflexion. This will be compared between pwMS and healthy controls. This study can add to the limited knowledge and possibly help to personalize and implement TENS in the clinic.
