The purpose of this study is to assess the safety and efficacy of the BrainPort balance device in improving balance and gait as measured by clinically accepted standardized balance assessments in subjects with peripheral vestibular dysfunction.

Peripheral vestibular dysfunction can be caused by inner ear disorders, drug toxicity, neuritis, or a number of other causes. In the absence of a fully functional vestibular system, the brain often requires retraining to correctly utilize visual and proprioceptive cues to maintain postural stability. People with vestibular dysfunction experience multiple problems with posture control and movement, including an unsteady gait and various balance-related difficulties. These effects make it very difficult to walk in the dark or on uneven surfaces without risk of falling. They are typically referred for conventional vestibular therapy. Many patients improve with therapeutic intervention. Some patients reach a plateau and do not return to their previous level of function. The BrainPort balance device transmits head position information via electrotactile stimulation of the tongue. With training, patients learn to use the positional information to correct their balance.

Participants meeting the study criteria will be randomized to the perceived stimulation or subliminal stimulation group. All participants will be given baseline assessments of postural stability, balance, and subjective well being according to standardized tests. After completing the baseline assessments, each participant will be trained in the clinic using a standard training protocol with the BrainPort balance device. Each participant will participate in 6 clinical training sessions, over a period of 3 consecutive days. Upon completion of the clinic training sessions, participants will continue with a 7½ week period of home use. During this period, the participant will train with the device for 20 minutes 2 times per day and the clinicians will contact the participants weekly. At the end of the home training period (8 weeks from the beginning of the study), all participants will again undergo the tests given at baseline.

Following the data analysis, subjects that have completed the 8 week study and were originally assigned to the group with inferior results will be given the opportunity to use the device that showed superior results in the data analysis.

Inclusion Criteria:

1. Confirmed diagnosis of peripheral vestibular dysfunction by the following (within 12 months of study enrollment):

   1. Bilateral Vestibular Hypofunction (BVH)-Sinusoidal rotary chair results at least 2 SD below normal across the frequency range of 0.01 to 0.32 Hz, and at least 60 deg/s peak velocity.
   2. Unilateral Vestibular Hypofunction (UVH)-Bithermal caloric test results of > 25% unilateral weakness.

2. Minimum post 3 months diagnosis with residual balance problems.

3. Previously treated with conventional physical therapy, and discharged and/or reached a plateau.

4. Functional Ability:

   1. Able to ambulate independently or with an assistive device for 20 feet.
   2. Ability to stand independently for 2 minutes with no or minimal upper extremity support.
   3. Dynamic Gait Index ≤ 19/24.

5. Able to read and sign the informed consent form.

6. Fluent in English.

7. Willing and able to complete all testing, training, and follow-up evaluations required by the study protocol.

Exclusion Criteria:

1. Current oral health problems as determined by health questionnaire and an examination of the oral cavity.

2. Any medical condition that would interfere with performance on the assessments.

3. Known neuropathies of the tongue.

4. Prior exposure to BrainPort balance device.

5. History of seizures or epilepsy.

6. If female, pregnant. Subject must deny pregnancy and agree to use appropriate birth control to prevent pregnancy for the duration of the study.

7. People with implanted electrical medical devices (i.e. pacemaker, deep brain stimulator).

8. People currently taking any vestibular suppressant medication (i.e. barbiturates, benzodiazepines, betahistines or cortisone).

9. People with a previous diagnosis of a central nervous system lesion (e.g. stroke or brain injury).

10. Current diagnosis of any of the following:

    1. Bilateral areflexia (no response to ice water caloric testing bilaterally)
    2. Progressive neurological disease (such as Multiple Sclerosis)
    3. Cervicogenic dizziness
    4. Pre-syncope/syncope episodes
    5. Orthostatic hypotension
    6. Mood Disorders (such as Major Depression and Bipolar Disorder)
    7. Anxiety disorders
    8. Hydrops / Ménière's

11. Principal Investigator, in his or her medical judgment, does not believe the subject is a good candidate for the trial.