Tinnitus is the perception of sound in the head or the ears. Typically, an individual perceives the sound in the absence of outside sounds, and the perception is unrelated to any external source. Clinically, subjective tinnitus is the perception of sound in the absence of auditory stimulation.
The findings are 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. It 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.
Estimates of patients with tinnitus range from 10-20% of the population (30-45 million people). Tinnitus in children has been reported as high as 18%.