Similarities between chronic pain and tinnitus.

OBJECTIVE: The aim of this study is to review hypotheses about the mechanisms of chronic pain and to compare them with that of tinnitus. Hypotheses about the pathophysiology of severe tinnitus and chronic pain have been of mainly two kinds: one of which claims that pathology located in the periphery (the ear for tinnitus, and peripheral nerves for pain) can explain the symptoms, while the other claims that the symptoms are caused by changes in the function of nuclei of the central nervous system. DATA SOURCES: A search of the literature from the past 35 years was used.
CONCLUSIONS: There is considerable evidence that both chronic pain and some forms of tinnitus are caused by changes in the central nervous system and that the anatomic location of the physiologic abnormality causing the symptoms of chronic pain and some forms of tinnitus is not the same location to which the symptoms are referred, i.e., the ear for tinnitus and the location of injury for pain. Such changes in the central nervous system may have been induced by peripheral processes such as tissue damage, but the changes can persist a long time after complete healing of a peripheral lesion. Different forms of tinnitus may respond to different treatments as is the case for chronic pain. If the different forms of tinnitus cannot be separated, then the results of studies of the efficacy of different kinds of drugs may be misleading.