When there is damage to any part of the path that sound takes through the hearing system, hearing ability may be compromised. A person is hearing impaired if there is a hearing loss less than 90 decibels (dB). In case of hearing loss of 90 dB or more, a person is deaf. .
Hearing impairment is divided into several categories:.
(1) conductive hearing loss--here, the problem is located in the outer ear or the middle ear. This is normally caused by cerumen (earwax), middle ear diseases or otosclerosis (the eardrum and the ossicles have increased mobility).
(2) sensorineural hearing loss--In this kind of hearing loss, the inner ear of the hearing nerve is affected. The loss is normally permanent and more in the higher frequencies than the lower frequencies. This type of hearing impairment is normally caused by congenital or inherited reasons, noise trauma, aging, trauma (head injury) or a tumor compressing the hearing nerve.
(3) Mixed--some combination of sensorineural and conductive hearing loss.
The most common cause associated with either of the categories are as follows:.
Family history of hereditary childhood sensorineural hearing loss.
In utero infection, such as cytomegalovirus, rubella, syphilis, herpes and toxoplasmosis.
Craniofacial anomalities, including those with abnormalities of the pinna and ear canal.
Birth weight less than 1,500 grams.
Hyperbilirubinemia at a serum level requiring exchange transfusion.
Bacterial meningitis.
Mechanical ventilation lasting 5 days or longer.
Stigmata or other findings associated with a syndrome known to include a sensorineural and/or conductive hearing loss.
Head trauma associated with loss of consciousness or skull fracture.
Neurodegenerative disorders.
Perforation of the ear drum.
Therapy for conductive hearing loss often involves treatment with medication or surgery. A person suffering from sensorineural hearing loss is best helped with the use of a hearing aid.