Nerve deafness, also known as sensorineural hearing loss, is a condition of the ear whose symptoms include decreased hearing ability or total deafness due to damage to the inner ear. It affects millions of people in varying degrees of severity. The condition may be the result of defects present at birth, called congenital defects, or acquired symptoms later in life. Most cases of nerve deafness are attributed to abnormalities of the hair cells located in the inner ear.
Irreversible damage to parts of the inner ear, specifically the hair cells found in the cochlea, distinguishes nerve deafness from other hearing loss conditions, although very rare cases of deficiencies in the auditory centers of the brain and cranial nerve have been discovered. . Damage to the brain's auditory processors leads to a more severe sensorineural deafness called central hearing loss, marked by an inability to interpret sounds so that speech becomes incomprehensible. Most cases of nerve deafness are caused by damage to the hair cells, preventing auditory information from being transmitted to the acoustic nerve and causing some degree of deafness. The number of abnormal hair cells determines the severity of hearing loss.
Injury or destruction of the hair cells in the inner ear can come from congenital sources, inherited dominant or recessive genes associated with hearing loss, or acquired external influences such as infection, disease, or trauma. Acquired nerve deafness has been linked to abnormalities and diseases of almost every organ system, the side effects of some medications, and physical injuries. Lifestyles that incorporate constant exposure to loud noise, such as blaring headphones on a daily basis, can also cause such trauma. Some acquired causes can trigger a rapid hearing loss called sudden sensorineural hearing loss that usually resolves within a couple of weeks.
Nerve deafness that develops from inherited dominant or recessive genes can be syndromic, which refers to hearing loss that occurs along with abnormal symptoms in other parts of the body, or non-syndromic. The presence of a dominant deafness gene in a family requires that only one parent carry and pass the gene to their children for it to manifest. This usually results in hearing loss that continues in family members from one generation to the next.
Accurate diagnosis of nerve deafness involves rapid screening tests for hearing and audiometry. If nerve deafness is discovered, electroacoustic hearing aids that are placed in or behind the ear can be used for mild to moderate cases. Profound hearing loss may require the use of a cochlear implant, which requires a surgical procedure to embed the internal component of the device.