May 2021 Flagstaff Business News
Karon Lynn, Au.D
The Johns Hopkins University School of Medicine has begun research into a treatment that involves a modified cochlear implant.
If you have ever had a bout of dizziness, you would empathise with an individual who experiences dizziness chronically. Most of us have had an episode of car sickness or sea sickness. Imagine being in that state all the time! It is one of the most debilitating symptoms a person can have. Their entire life is consumed by the sensation of vertigo and coping with the nausea and disorientation it causes.
Drugs to treat vertigo are designed to reduce the sensitivity of the balance organs and usually have the side effect of making the person groggy or sleepy. In some conditions, the drugs are not helpful at all. Chronic vertigo can be caused by many conditions, including circulation issues, low blood pressure, dysfunction of the inner ear (vestibular systems), medication side effects, trauma to the head or neck and viruses, which cause damage to the vestibular system. The vertigo may start out slowly and cause dizziness intermittently or suddenly begin and stay all day and never go away.
One type of dizziness is called bilateral vestibular hypofunction, or BVH. Bilateral (both ears), vestibular (balance organ) hypofunction (the organs work but not correctly). It is estimated that about 1.8 million people have this disorder. Because humans use multiple inputs to navigate the world, having one input disrupted is a tremendous disadvantage. People with BVH are at risk for falls and have to concentrate on their balance to walk, bend over, stand up and sit down during their daily activities.
As a person moves, the brain receives information from a few different sensory systems such as vision, muscles and joints and, finally, sensations from the inner ear balance areas. People with BVH have difficulty keeping their eyes, head and body steady. Head movements make their vision jump and blur, which makes walking a challenge. It creates significant stress because the individual needs to concentrate to walk, and if they don’t, down they go. Because the current medicines cause a degree of sedation, people are encouraged to avoid driving, swimming and walking on uneven surfaces. People with BVH are 30 times more likely to suffer a fall than their peers.
The Johns Hopkins University School of Medicine has begun research into a treatment that involves a modified cochlear implant. The multichannel vestibular implant (MVI) is designed to stimulate the balance nerve long-term, which makes it a 24-hour-per-day sensory restoration treatment. The implant electrode bypasses the malfunctioning area of the inner ear and stimulates the vestibular nerve in response to signals. The vestibular nerve is located very close to the hearing nerve; essentially, in the same area of the head. The implant is designed to help people with damage to the delicate anatomy that makes up the vestibular system. The inner ear has three tiny structures called semicircular canals that track the head’s rotation along three axes (imagine nodding, shaking your head and tipping your left or right eyebrow up). Fluid in these canals pushes on sensory hair cells that change the mechanical signal to an electrical one in order to send information up the vestibular nerve. This implant restores most of the ability to walk, move and turn the head without dizziness. It helps people with BHV orient themselves in space!
The MVI is comprised of two parts. There is an implanted device that stays just under the skin above the ear with its electrode embedded in the vestibular nerve and an external motion sensor device that sends signals inside to the electrode. The external device is designed to send information about the speed and direction of any head motion. A tiny gyroscope is used to track the person’s head rotations in three dimensions, and a processor, which sends the rotational data to the internal implant to electrically stimulate the vestibular nerve. The implant uses nine electrodes to convey the information that would normally come from the three semicircular canals. This initiates head and eye reflexes that help maintain clearer vision during head movement and reduce the need to exert conscious effort to walk.
This research group has implanted eight people. All of the candidates already had hearing loss in the ear that was implanted. Some of the recipients lost more hearing in the implanted ear after the surgery and some of them maintained the hearing they had prior to the surgery. With these successful results, we hope that the industry will be able to offer this procedure to more individuals in the next few years!