Abstract
Sudden deafness is a dramatic and relatively common otological problem. The etiology in most cases remains unresolved although virus involvement has strong support. Sudden deafness has been associated with mumps, rubella, the respiratory and herpes groups of viruses as well as other more rare ones like hantavirus and Lassa virus. Perhaps the bestknown example of virus-induced sudden deafness is acute unilateral hearing loss associated with mumps virus infection. Mumps virus has also been isolated from the inner ear suggesting a direct virus-induced cytolytic mechanism for deafness. Herpesviruses are neurotropic and they have a tendency to become chronic. Therefore they have been strong candidates for viruses being responsible for acute hearing loss. Although serological associations have been found in certain studies, convincing evidence for the involvement of herpes and varicella-zoster viruses as agents causing direct cochlear damage and hearing loss in humans is missing. A number of case reports have associated sudden deafness to rubella, adeno- and hantavirus infections. Multiple studies showing no association of viruses with sudden deafness may reflect seasonal, geographical or epidemiological differences in this disease. This may also bring up the possibility of other etiological factors such as general inflammatory or autoimmune mechanisms for the disease. Histopathological changes in the affected ears are characterized by abnormal cellular architecture in the inner ear with loss of apical and spiral ganglion cells and destruction of the organ of Corti. Similar histopathological changes have been found in experimental animal models infected with mumps, rubella or herpesviruses. Histopathological observations could favor the theory of viral etiology in idiopathic sudden deafness but do not rule out the possibility of immunological disturbances, which would lead to similar histopathological changes.