Nosology of deafness.

It is estimated that about one half of all congenital deafness and/or hearing impairment is inherited and that approximately one third of this communicative disorder is associated with syndromic abnormalities. The remainder of inherited deafness occurs as an isolated entity, independent of alterations in physical status or any disease process. This latter group typically presents with no clinical signs or symptoms or other dysmorphic stigmata that might help in the early identification of hearing loss. As contemporary advances in genetic testing and therapy emerge, there is an ever-increasing opportunity to provide improved diagnosis and counseling to those with inherited disorders. Over the past 3 decades, there have been several distinct categorical systems introduced to define deafness. Most often, the nosology of deafness is described by either origin, onset, degree and type of severity, and/or structural pathology. Therefore, understanding the cause and nature of hearing loss is the first measure in the accurate diagnosis and management of patient care. This article describes several classification schemata, citing examples of numerous congenital syndromes and other disorders that contribute to deafness.