The goal of this clinical trial is to learn if stimulating the vagus nerve in combination with a motor task in people with multiple sclerosis can improve motor function. The main questions it aims to answer are:

• Is stimulating the vagus nerve safe and feasible after demyelinating episodes?
• Does a paired motor task with vagus nerve stimulation improve motor function with someone who has multiple sclerosis?

Researchers will compare active vagus nerve stimulation to a sham stimulation to see if the paired vagus nerve stimulation can improve motor control.

Participants will:

• Come in for study visits over a six month period. Study visits are three times weekly for the first month, then single follow up visits at two, three, and six months.
• During study visits, participants will complete 30 minutes of the paired vagus nerve stimulation with a motor task, specifically the grooved peg test.
• At various timepoints throughout the study, motor, disability, and neurophysiological assessments will be administered, including the Timed 25-Foot Walk Test, Expanded Disability Status Scale (EDSS), Upper Extremity portion of the Fugl-Meyer Assessment, Dellon-Modified Moberg Pick-Up Test, Multiple Sclerosis Impact Scale-29 (MSIS-29), motor evoked potentials (MEPs), and visual evoked potentials (VEPs). MRI assessments will also be performed to evaluate exploratory imaging metrics of potential remyelinative efficacy.

Inclusion Criteria:

• All participants ages 18-70 with diagnosis of multiple sclerosis at least 30 days from last relapse
• Baseline grooved peg test time greater than or equal to 91 seconds for completion of the task (2 standard deviation above mean multiple sclerosis score).
• Ability to sign informed consent
• Expanded disability status scale score (or estimated) of 2.5 or greater OR a clinical report of upper extremity dysfunction in their dominant hand

Exclusion Criteria:

• Current uncontrolled and/or clinically significant medical condition.
• History of seizures or epilepsy.
• Other central nervous system disease or significant brain trauma.
• Bacterial or viral infection within the prior 30 days.
• Prior treatment with total body irradiation, clemastine, bexarotene, or other experimental remyelinating agent.
• Recent suicide attempt or continued expressed suicidal ideation.
• Implanted devices, such as pacemakers, cochlear prosthesis, neuro-stimulators.
• Abnormal ear anatomy or ear infection.
• Pregnancy, lactation, or lack of use of contraception.
• Unable to walk 25 feet continuously
• Other significant disease or disorder that might impair study participation. Participants will be allowed to initiate or maintain background disease modifying therapy to reduce the risk of multiple sclerosis relapse and optimize recruitment.