Pathogenesis

The mechanism of tinnitus is yet to be completely understood (1)

The pathogenesis of tinnitus is dependent on site and it can begin at any location from the cochlear nucleus to the auditory cortex (1).

Normally, external sounds result in a change of rate or pattern of the continuous incoming stream of cochlear neuronal signals. These changes are interpreted as sound by the brain. The sensation of tinnitus is felt by a person when such changes occur continuously. These changes may arise either spontaneously or as a result of some triggering event (2).

Several theories exist as to the causation of idiopathic tinnitus:

• the cochlear hypothesis: damaged outer hair cells within the cochlear apparatus become disinhibited leading to an overamplification of the ambient noise
  
  
• Moller's hypothesis: tinnitus is caused by demyelination in the vestibulocochlear nerve
  
  
• tinnitus is generated by spontaneous otoacoustic emissions; only thought to prevail in 4% of patients and responds to aspirin

Reference:

• (1) Crummer RW, Hassan GA. Diagnostic approach to tinnitus. Am Fam Physician. 2004;69(1):120-6l
• (2) British Tinnitus Association 2005. Update on the management of tinnitus by audiologists