Study of Safety and Effectiveness of PoNS Device to Treat Chronic Balance Deficit Due to Traumatic Brain Injury (TBI)

Inclusion Criteria: * Male or female, 18-65 years of age * Documentation on initial TBI (defined as closed-head, non-penetrating, blunt, whiplash, or explosive blast-induced brain injury) severity (at time of injury): Glasgow Coma Scale (GCS) score 9-15, with loss of consciousness \< 24 hours, post-traumatic amnesia ≤7 days, or hospital admission ≤ 7 days post TBI * If female, subject is not pregnant, not lactating, has a negative pregnancy test prior to receipt of the PoNS™ device, and agrees to use contraception from screening to end of the study * Balance disorder with SOT composite score at least 16 points below normal resulting from a mild/moderate TBI without any concomitant pathologies * At least 1 year post injury * Stable neurologic status * Prior participation in a focused physical rehabilitation program for TBI and deemed by their treating clinician/themselves to have reached a plateau * Able to walk continuously on a treadmill for 20 minutes, level grade and at any speed, with support if needed * Access to a treadmill and commitment to utilize this for the at-home portion of the study * Able to understand the study procedures and give informed consent * Willing and able to adhere to the study schedule * Willing to complete a neuropsychological evaluation prior to inclusion Exclusion Criteria: * Medical finding from screening history and physical examination that is clinically significant or would otherwise impact patient safety or data integrity * Medical finding from prior neuroradiologic study or recent MRI that is significant or that would impact patient safety or data integrity * Planned use or use of any investigational product, pharmaceutical or device within 30 days preceding receipt of the PoNS device and during the entire study * Balance or gait deficits due to lower extremity injury or neurological condition other than TBI * Penetrating brain injury, craniotomy or refractory subdural hematoma * Oral health problems at the time of recruitment * Oral surgery within 3 months of screening * History of oral cancer * Non-removable metal orthodontic devices that could interfere with PoNS use * Presence of metallic implant or other MRI-incompatible device * Blood pressure abnormalities considered clinically significant * Use of Coumadin or other anticoagulant except aspirin in the last 6 months * Untreated or undiagnosed diabetes * Diabetic neuropathy * Active or recent (within 1 year) treatment for any cancer, excluding basal cell carcinoma. * Neurological disorders other than those attributed to the primary diagnosis (neurodegenerative diseases such as Multiple Sclerosis, Parkinson's disease, Alzheimer's disease or other dementia, Amyotrophic Lateral Sclerosis) * History of epileptic or other seizure disorders * Known ischemic heart disease and/or history or atrial or ventricular arrhythmias with or without syncope * Any other untreated or unstable acute or chronic, clinically significant medical condition for which the subject is currently undergoing treatment that the study investigator deems unsuitable for inclusion * Use of a lower extremity biomechanical prosthetic with the exception of a splint for foot drop * Females who are pregnant, lactating, or planning to become pregnant during the study * Chronic use of any potentially interfering medication, or use of any medication that would compromise the ability to function or perform the study activities * Addition of and/or major change in type or dosage of any prescription medication within 3 months prior to receipt of the PoNS device * Active alcoholism. The study investigator will have the right to exclude subject participation if the subject seems intoxicated at time of screening and/or during any study appointment. * History of drug abuse will be assessed * Recent history of smokeless tobacco use * Any reason that may be a threat to health or safety * Any finding in the neuropsychological evaluation that makes the subject unsuitable for inclusion