Update on tinnitus.

The study of a disorder such as tinnitus is fraught with difficulties. Tinnitus, like pain, is a subjective symptom. The problem is compounded because several different mechanisms must operate to cause the persistent sensation of tinnitus. Therefore, it is difficult to measure objectively any improvements in the condition. For example, it has been reported previously that sectioning the eighth cranial nerve does not abolish tinnitus in a majority of patients; therefore, central mechanisms must act to preserve the tinnitus. Finally, we know that tinnitus can occur in a host of conditions other than ototoxicity, aging, and noise exposure. Other conditions that may produce tinnitus are migraine headache with auditory aura, temporal lobe seizures, and head injuries. Therefore, it is naive to conceptualize that tinnitus is a disorder with a unitary origin and a unitary "cure".