What is Tinnitus?
Tinnitus is sound or noise originating in the ears or head. The most common form is called subjective tinnitus which means only the person who is experiencing tinnitus can hear it. Many times patients with tinnitus are amazed that others cannot hear it. Objective tinnitus is tinnitus which can actually be heard by others if they put their ear to yours. There is a long list of causes of tinnitus. Tinnitus can be caused by ear infections, excessive ear wax, damage to the ear drum (tympanic membrane), middle ear disease, sensorineural hearing loss (nerve damage), aging, cervical neck disease, tmj, aspirin, ear trauma, excessive noise exposure, increased intracranial pressure, Meniere's disease, acoustic nerve tumors, brain tumors, and unusual medical conditions such as advanced syphilis. Estimates of patients with tinnitus range from 10-15% of the population (30-40 million people). 85% of patients with ear disease experience tinnitus.
Jastreboff and Hazell suggest that tinnitus may occur at any level from the cochlea (inner ear) to the cortex (brain). Hyperactivity or damage to the cochlear hair cells results in senseless signals which are translated by the brain as a phantom hearing sensation. Tinnitus resulting from damage to the ear would be called peripheral tinnitus while that caused by the central nervous system would be called central tinnitus. The biggest cause of tinnitus by far is due to damage to the receptor cells in the inner ear. The concept of what happens is related to the idea of phantom pain. With phantom pain people who have had their foot amputated sometimes report that their foot hurts even though they no longer have a foot. Why is this? The explanation has to do with how our central nervous system deals with missing input from peripheral nerves, in this instance your foot. Every neuron in your body sends information to the central nervous system. When those neurons are not present, the central nervous system misses them and in turn puts that "sensation" back. In the case of the foot, it is pain or a tactile sense.
With tinnitus we believe that the damaged or missing receptor cells (hair cells) stop sending signals to the brain, and the hearing centers in the brain miss the input from those cells. The receptors in the brain then look for any input and amplify it. There is a lot of electrical activity in the brain. When some electrical signal is erroneously detected and then amplified, you hear a sound, tinnitus, even though there is not an actual sound present.