Causes of Tinnitus
Tinnitus is ringing, buzzing, roaring, or other sound in the ear. For some it comes and goes, and for many it is permanent in one or both ears. Millions of Americans suffer from tinnitus, and far too many have been told that there is nothing to do but live with it. While this may have once been true, research has come a long way in recent years and new treatment methods are very effective.
DIFFERENT WAYS THAT TINNITUS CAN HAPPEN
It is generally not possible to determine for any given individual which particular mechanism is the cause of their tinnitus. Fortunately, treatment is the same regardless of the cause and is very effective.
MISFIRING COCHLEAR HAIR CELLS
Inside the cochlea (in the inner ear as described on the How Hearing Works page) are row upon row of 20,000 hair cells that transform mechanical sound vibrations into electrochemical nerve impulses.
The way this mechanism works is that as fluid is churned in the cochlea from vibration coming from the middle ear bones, the fluid rushes past these hairs and causes them to bend. The bending of these hairs opens a trap door underneath them, allowing the potassium-rich fluid they live in to reach a sodium-filled fluid underneath, and potassium mixed with sodium makes electricity. This electrical charge is then carried up the hearing nerve to the brain where sound happens.
When these hair cells become damaged, they lay flat as shown in the bottom picture to the right. When hair cells are permanently out of place, there is a constant mixture of the two fluids that the hair cells are meant to keep apart, and this constant mixture results in a continuous firing of the hearing nerve. Because each of these hair cell bundles represents a specific pitch of sound, the ringing has a pitch which corresponds to the area of greatest damage.
It is generally accepted that this is the mechanism of tinnitus associated with noise damage or ototoxic medications because these cause physical damage to the basilar membrane of the cochlea, where the hair cells are located.
AUDITORY DEPRIVATION AND NEURAL HYPERSENSITIVITY
Brains like input. Neurons like to be stimulated. This includes the auditory neurons in the temporal lobe. Just like the cochlea, the auditory cortex it tonotopically organized, meaning that each neuron is responsible for a different pitch. This means that when hearing loss happens, certain neurons lack input in the specific frequency regions where the hearing loss is most severe. As you can see in the image to the right, neural stimulation happens in relatively large regions, not generally one neuron at a time.
The portion of the brain responsible for hearing is close to other regions, and if an auditory neuron is not getting input from the hearing nerve, it might well pick up electrical activity in an adjacent region and respond. Since that neuron is responsible for sound at a certain pitch, when it fires in response to adjacent activity it sounds like a ringing sound at the pitch that neuron represents.
DIET OR MEDICATIONS
Tinnitus can also be caused by things we swallow, be it caffeine, salt, or prescription or over-the-counter medications. Aspirin is a very common medication that has been linked to tinnitus, and if there is an alternate blood thinner that your doctor can put you on it can often eliminate the ringing.
Other health conditions such as high blood pressure and diabetes have also been linked to tinnitus. Be sure to have regular physicals to ensure that all such issues are identified and addressed appropriately.