What is the pathophysiology of tinnitus?

Updated: Feb 27, 2020
  • Author: Aaron G Benson, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
  • Print
Answer

Answer

Clinically, subjective tinnitus is the perception of sound in the absence of auditory stimulation. In terms of neurophysiology, tinnitus is the consequence of the brain’s response to input deprivation from the auditory periphery. In the healthy auditory system, there is an ordered tonotopic frequency mapping from the auditory periphery (cochlea), through the midbrain, to the auditory cortex. When a region of the cochlea is damaged, the subcortical and cortical projections adjust to this chronic lack of output (plasticity), and the tonotopic organization is altered. In the auditory cortex, the region that corresponds to the area of cochlear damage is termed the lesion projection zone (LPZ). After cochlear damage, neurons in the LPZ show 2 important changes: an increase in the spontaneous firing rate and an increase in the frequency representation of the neurons that border the region of damage (the so-called lesion edge frequencies).

Tinnitus model. Two phenomena in the auditory cort Tinnitus model. Two phenomena in the auditory cortex are associated with peripheral deafferentation: 1) hyperactivity in the lesion projection zone and 2) increased cortical representation of the lesion-edge frequencies (here, C6) in the lesion projection zone. These two phenomena are presumed to be the neurophysiological correlates of tinnitus. The red letters correspond to octave intervals of a fundamental frequency.

These findings are explained in terms of a) the loss of central inhibition on the regions that are damaged and b) cortical plasticity of the neighboring regions of the cortex that are still active. Hence, tinnitus neurophysiology is related to detrimental cortical adaptation to input deprivation from the sensory periphery.

Additional data from animal and human studies have suggested that tinnitus may be associated with neuronal hyperactivity at different levels of the central auditory pathways, including the dorsal cochlear nucleus, the inferior colliculus, auditory cortex, and the striatum.

A literature review by Tegg-Quinn et al indicated that tinnitus can cause cognitive difficulties in adults by affecting executive control of attention. [2]  A prospective study by Gudwani et al also suggested that an association exists between tinnitus and cognitive problems. The report, which involved 25 patients, indicated that chronic, subjective tinnitus has a particularly deleterious effect on digit-span tests, verbal comprehension, mental balance, attention and concentration, immediate recall, visual recognition, and visual-motor gestalt tests. [3]


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!