How do we Hear ?
Better understanding of hearing and hearing loss begins by understanding how we hear. Sound waves are collected by the outer ear and channeled along the ear canal to the eardrum. When sound hits the eardrum, the impact creates vibrations that cause three bones in the middle ear to move. The smallest of these bones, the stapes, fits into the oval window between the middle and inner ear. When the oval window vibrates, fluid in the inner ear transmits the vibrations into the hearing organ, called the cochlea.
In the inner ear, thousands of microscopic hair cells are bent by the wave-like action of fluid inside the cochlea. The bending of these hairs sets off nerve impulses that are then passed through the auditory nerve to the hearing center of the brain. This center translates the impulses into sounds the brain can recognize.
How do I know I have hearing loss ?
Hearing loss is usually gradual, developing over a long period of time. At some point, the deterioration of hearing starts to interfere with conversational speech in many places. If you answer "yes" to many of the following questions, you may have hearing loss:
Types of Hearing Loss
Conductive hearing loss: This occurs when the outer or middle ear fails to work properly. Sounds become "blocked" and are not carried all the way to the inner ear. Conductive hearing losses are often treatable with either medicine or surgery. Common causes are fluid behind the eardrum or wax build-up in the ear canal. Conductive hearing loss also can occur when the eardrum or bones of the middle ear are disrupted, result of an upper respiratory tract infection may affect patency of the Eustachian tube (a small tube like structure that connects the middle ear to the nose), Presence of a foreign body, Absence or malformation of the outer ear, ear canal, or middle ear and acoustic trauma.
Sensory hearing loss: This occurs when the inner ear is damaged. The most common causes are congenital cochlear deformity, genetic syndromes, aging, inner ear infection and noise exposure, meniers disease. This type of hearing loss is usually not medically or surgically treatable.
Neural hearing loss: This occurs when there is damage to the hearing nerve or the nervous system. The inner ear generates neural impulses that travel through the hearing nerve to the brain. Aging can cause degeneration of the hearing nerves,meningities, ototoxicity, and tumor pressurizing the auditory nerve.
Mixed Hearing Loss: Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss. In other words, there may be damage in the outer or middle ear and in the inner ear (cochlea) or auditory nerve. When this occurs, the hearing loss is referred to as a mixed hearing loss. Common cause can be otosclerosis.
Causes of hearing loss
Age : Advancing age is the most common cause of hearing loss.
Disease : Meningitis, Meniere's Syndrome, benign growths and tumors on the hearing nerve. Viral infections such as mumps and measles.
Drugs : Some drugs and antibiotics can cause damage to hair cells in the inner ear and the auditory nerve. Some of these drugs include, but are not limited too, quinine, aminoglycosides, diuretics and aspirin in large dosages.
Infections : Otitis media is a middle ear infection characterized by the formation of fluid in the middle ear. This can be caused by allergies, head colds, inflamed tonsils and adenoids, blocked eustachian tubes, sore throats and other viruses.
Malformation : A malformation of the ear canal can sometimes cause a hearing loss.
Noise : Noise exposure (hunting, factory/plant noise, engine noise) can cause permanent hearing loss. Perforation: Perforation of the eardrum can be caused by a change in air pressure associated with flying or scuba diving, a foreign object such as a cotton swab used to clean the ears or pressure caused by a middle ear infection.
Wax : Wax can build up in the ear canal and cause a blockage, which will stop sound from passing through the ear canal. A physician, nurse or audiologist can periodically remove the ear wax. (Cotton swabs or sharp objects should never be used to clean the ears because they can push the wax deeper into the ear and may puncture the eardrum).