Abstract
(First paragraph) Hearing loss is a condition affecting people of all ages and can be categorized as either conductive or sensorineural. Conductive hearing loss is caused by pathology of the middle ear and will not be addressed in this volume. Our focus here is on sensorineural hearing loss, or hearing loss caused by pathology of the inner ear. Sensorineural hearing loss can be either inherited or acguired and congenital or late onset. Over 400 syndromes have been described that demonstrate hearing loss along with a variety of other anomalies. A few of the most common hereditary hearing loss syndromes include Branchi- oto-renal (caused by mutations in Eya1 and Six1), Waardenburg’s (mutations occur in the Pax3 and MITF genes, among others), Pendred's (caused by a mutation in the PDS /pendrin gene) and Usher’s (caused by a mutation in one of several USH genes) Syndromes. In addition, over 70 different genes have been described that produce non-syndromic hearing loss. These genes code for a variety of protein products including structural proteins, ion channels, and transcription factors. Acguired sensorineural hearing loss can be caused by trauma to the inner ear, environmental auditory insults, ototoxic medications and idiopathic sudden sensorineural hearing loss, and presbyacusis (hearing loss in elderly patients). The vestibular portion of the inner ear is also susceptible to disease including Meniere's disease, vestibular neuronitis, and benign paroxysmal positional vertigo (Snow, 2003).