Etiology and Rehabilitation of Sensorineural Hearing Loss

Abstract

Hearing is a special sense by which we perceive sound by detecting vibrations. Hearing ability is important for us to be able to interact, communicate and socialize. Sound is captured by the human ear which is a peripheral sensory organ composed of the external ear, middle ear and inner ear. The external ear serves to focus sound energy through the external auditory canal toward the tympanic membrane. The middle ear amplifies the sound energy via the ossicular chain which transfers sound vibrations to the inner ear. The inner ear includes the cochlea where mechano-electrical transduction of sound energy takes place. Humans perceive the vibrations of sound as transient auditory signals of vibratory mechanical forces transmitted through the external ear and middle ear, where they are transduced to neural signals in the inner ear passing via the auditory nerve to the central auditory system of the auditory cortex where the signal is processed and interpreted and passed on for perceptive processing. Understanding the central auditory processing in the central nervous system is essential to understanding how the sound information is discriminated and analysed to allow good communication. Any single problem in the peripheral or central auditory pathway may cause hearing impairment. Conductive hearing loss is defined as the hearing loss due to inappropriate mechanical transmission. Conditions that can cause conductive hearing loss are foreign body obstruction of the external auditory canal, perforation of the tympanic membrane, middle ear effusion, the destruction of ossicles, etc. Depending on the specific cause of conductive hearing loss, medical or surgical treatment can restore hearing. Sensorineural hearing loss refers the hearing loss caused by inner ear problems such as hair cell damage or neural degeneration. Unlike the conductive hearing loss, sensorineural hearing loss is usually permanent. Sensorineural hearing loss is divided into congenital and acquired. Congenital hearing loss may be caused by a congenital anomaly, a chromosomal syndrome or a congenital infection such as rubella or cytomegalovirus. Acquired sensorineural hearing loss might have numerous etiologic causes, including