Hearing loss can be caused by a blockage of sound to the inner ear or damage to the inner ear. Hearing loss that is due to a blockage is called conductive hearing loss. Conductive hearing loss is not typically considered permanent hearing loss.

A hearing loss that is caused by damage to the inner ear is called sensorineural hearing loss. Though conductive hearing loss can often be medically corrected by repairing or removing the cause of the blockage, sensorineural hearing loss is considered permanent. Permanent hearing loss can vary in degree from mild difficulty to deafness.

The causes of permanent hearing loss are damage to the cochlea or auditory nerve. Sensorineural hearing loss can be present at birth or acquired later in life. Causes of sensorineural hearing loss that is present at birth, also called congenital hearing loss, can be due to normal heredity, deformity, or chromosomal abnormality.

If the mother contracts an intrauterine infection or has toxemia during the pregnancy, the fetus may develop congenital hearing loss. Prematurity, a lack of oxygen during or after birth, and maternal diabetes make the newborn susceptible to permanent hearing loss.

Damage to the inner ear or auditory nerve can be due to traumatic injury such as a car accident or violence. In some cases, permanent hearing loss is due to exposure to toxic chemicals. This is called ototoxicity.

Exposure to loud noise and the effect of aging can cause permanent hearing loss. Occupational hearing loss is sensorineural hearing loss from exposure to loud noises in the work environment. Some careers such as working in an industrial setting and musicians are prone to occupational hearing loss.

Some infections are potential causes of permanent hearing loss. Meningitis, influenza, chicken pox, measles, mumps, and encephalitis have been identified as possible causes of acquired permanent hearing loss.

Some people develop sudden hearing loss without an identifiable cause. This sudden, unexpected hearing loss is called idiopathic hearing loss. In many cases, the hearing loss subsides as mysteriously as it developed. Idiopathic hearing loss can be permanent. There is no universally accepted treatment for idiopathic hearing loss though it is often treated with steroids.