Birmingham Tinnitus Care and Auditory Therapies 

Discordant Dysfunction Theory

The Discordant Dysfunction Theory was proposed by PJ Jastreboff (1990) as an explanation of  the source of tinnitus.

Within the inner ear there is snail shell shaped structure called the cochlea. Within this structure is housed thousands of tiny hairs cells which respond to sound and send impulses through the auditory nerve to the brain. Eventually these impulses are registered in the auditory cortex of the brain as sound.

There are two sets of hair cells within each cochlea. The outer hair cells act as a mechanical amplifier within the cochlea making it possible to detect quieter sounds.

The inner hair cells respond to louder sounds. 

Both the outer and inner hair cells within the cochlea send information to the brain via the auditory nerve.

When there is damage to the hearing system it is the outer hair cells which are damaged first. The resulting imbalance between the messages sent from these two types of hair cells causes an imbalance in part of the brainstem within the brain called The Dorsal Cochlear Nuclei and The Inferior Colliculus.

The increase in neural activity in these areas of the brain is further amplified within the auditory system and is perceived as tinnitus.

A  hearing loss causes the auditory system to attempt to compensate for the hearing loss. The hearing system is attempting to restore balance. Hearing loss causes an increased firing rate in the nerves of the central auditory system, this increase in spontaneous activity is detected as tinnitus.

For many people affected by tinnitus, it is simply a side effect of a normal compensation mechanism within the auditory system in a response to hearing loss.

Normal Hearing and Tinnitus

It is thought that damage to the outer hair cells can occur with no measurable hearing loss. Even very minor damage to the outer hair cells can result in the imbalance outlined above, resulting in tinnitus.

Hearing tests normally measure hearing over the range of frequencies from 250Hz to 8,000 Hz. A measurable hearing loss could be present beyond the frequency range that is typically measured during a hearing test resulting in tinnitus perception.