EAR DISEASE

any of the diseases or disorders that affect the human ear and hearing. Impaired hearing is, with rare exception, the result of disease or abnormality of the outer, middle, or inner ear. Serious impairment of hearing at birth almost always results from a dysfunction of the auditory nerve and cannot be improved by medical or surgical treatment. In early and late childhood the most frequent cause for impaired hearing is poor functioning of the eustachian tubes with the accumulation of a clear, pale yellowish fluid in the middle-ear cavity, a disorder called serous, or secretory, otitis media. In early and middle adult life the usual cause for progressive impairment of hearing is otosclerosis. The usual cause of hearing loss after the age of 60 is presbycusis, a disorder that results from the aging process. In most cases when loss of hearing is due to a problem with sound conduction, surgical restoration can correct the defect and restore hearing. When loss of hearing is the result of nerve damage, however, surgery is not of use. Medical treatment of auditory nerve damage is helpful only in rare casese.g., when the loss is due to syphilis or an early case of Mnire's disease or in some instances when zinc deficiency is the underlying cause. More important than a cure for auditory nerve damage is prevention. Cases of deafness in the newborn due to rubella (German measles) in the mother can be averted with the rubella vaccine. Nerve damage caused by exposure to excessive and prolonged noise is preventable by early detection. One approach is to give routine hearing tests to individuals who work in environments where excessive noise is unavoidable. The incidence of impaired hearing in the general population depends on the degree of hearing loss defined as impaired (see ear: The physiology of hearing: Hearing tests: Audiometry). According to U.S. statistics, by age 6, 0.2 percent of all children have impaired hearing in one or both ears that is sufficient to warrant consultation of an ear specialist. By age 18 the number of children with hearing loss sufficient to require diagnostic examination reaches 2.5 to 3 percent. By age 65 the number of adults with a recognizable hearing impairment reaches 5 percent. After age 65 the incidence of impaired hearing rises rapidly. About 30 to 35 percent of individuals between the ages of 65 and 75 and 40 percent of those older than 75 are affected by hearing loss. Comparable figures from Great Britain show that 1 in 6 persons is estimated to have some hearing difficulty, but only one-fourth of these have any real handicap, with one-third of this latter group needing hearing aids and 1 in 20 being deaf to all speech and beyond help with a hearing aid. Of British children, 1 in 1,000 is severely deaf, and as many as 7 per 1,000 are estimated to have a level of impairment that requires some form of help. The structure and function of the human auditory and vestibular systems are treated in the following sections from the ear article: Anatomy of the human ear, The physiology of hearing, and The physiology of balance. This article deals with the more important diseases and disorders of the outer, middle, and inner ear. Additional reading Ear diseases and hearing disorders are discussed in Michael E. Glasscock III, George E. Shambaugh, Jr., and Glenn D. Johnson (eds.), Surgery of the Ear, 4th ed. (1990), a well-illustrated text on diseases of the ear and their surgical correction; James Jerger (ed.), Hearing Disorders in Adults (1984); John Ballantyne, M.C. Martin, and Antony Martin (eds.), Deafness, 5th ed. (1993); Robert Thayer Sataloff and Joseph Sataloff, Hearing Loss, 3rd ed., rev. and expanded (1993); and David M. Vernick et al., The Hearing Loss Handbook (1993). George E. Shambaugh, A Restudy of the Minute Anatomy of Structures in the Cochlea with Conclusions Bearing on the Solution of the Problem of Tone Perception, The American Journal of Anatomy, 7(2):245257 (Aug. 1, 1907), was the first detailed description of the hearing-nerve end organ in the cochlea, where sound waves are converted into nerve impulses depending upon the pitch of the tone. George E. Shambaugh, Jr., and Alexandre Petrovic, Effects of Sodium Fluoride on Bone: Application to Otosclerosis and Other Decalcifying Bone Diseases, JAMA, 204(11):969973 (June 10, 1968), summarizes research on the arrest, by means of sodium fluoride, of progressive deafness caused by otosclerosis. Philip H. Beales, Noise, Hearing, and Deafness (1965), is a useful review in lay language of the problem of deafness and the adverse influence on hearing of excess noise exposure; a more recent text is Karl D. Kryter, The Handbook of Hearing and the Effects of Noise: Physiology, Psychology, and Public Health (1994). Brief reports by panels of experts assembled by the National Institutes of Health are issued as NIH Consensus Statements; several statements are of clinical concern in the field of hearing and deafness: Noise and Hearing Loss, 8(1):124 (Jan. 2224, 1990), also available with the same title in JAMA, 263(23):31853190 (June 20, 1990), Early Identification of Hearing Impairment in Infants and Young Children, 11(1):124 (Mar. 13, 1993), and Cochlear Implants in Adults and Children, 13(2):130 (May 1517, 1995), also available with the same title in JAMA, 274(24):19551961 (Dec. 27, 1995). More information on the success of cochlear implants is available in Jeffrey P. Harris, John P. Anderson, and Robert Novak, An Outcomes Study of Cochlear Implants in Deaf Patients, Archives of OtolaryngologyHead and Neck Surgery, 121(4):398404 (April 1995). George E. Shambaugh