There are many causes of tinnitus, and the origin of many incidences of tinnitus is unknown. A common cause of severe tinnitus is deprivation of signals to the central auditory system (see Chap. 11). This may occur through conductive hearing loss, cochlear hearing loss, and pathologies of the auditory nerve. The relation between tinnitus and hearing loss is discussed in Chap. 35 (see also Chaps. 8 and 10).