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There are many known causes and degrees of hearing loss which is defined as a deterioration of hearing. This condition may be caused by a mechanical problem in the ear canal or middle ear that has blocked the conduction of sound. It may also be caused by damage to the inner ear, auditory pathways in the brain or auditory nerve. When the conduction of sound is affected this is known as conductive hearing loss. If there is damage to the inner ear, auditory nerve or its pathways to the brain the hearing loss is called sensorineural hearing loss. Both types of hearing loss can be easily distinguished when a doctor compares the difference in how well a person can hear sounds that are conducted by air to those conducted by bones.
When the inner ear is affected the sensorineural hearing loss is categorized as sensory, but when the auditory nerve or auditory nerve pathways in the brain are affected the hearing loss is called neural. It is believed that sensory hearing loss is hereditary or caused by loud noises which is also known as acoustic trauma. Other causes thought to be responsible for sensory hearing loss might include viral infections of the inner ear, certain drugs or Meniere's disease. With neural hearing loss it is believed that such factors as brain tumors causing damage to nearby nerves and the brain stem, some infections, various brain and nerve disorders and some hereditary diseases could be responsible. Mumps, German measles, meningitis or inner ear infections during childhood have been known to damage the auditory nerve causing hearing loss and the auditory nerve pathways in the brain are sometimes damaged by diseases that destroy the nerve covering.
Several hearing tests are available to measure the amount of hearing loss and although a tuning fork test can be performed in a doctor's office the best test are done in a sound proof booth by an audiologist. In adults hearing by air conduction is tested by placing a vibrating tuning fork near the ear and hearing by bone conduction is done by placing the base of a vibrating tuning fork against the head. Using these two test an audiologist can tell if the problem is in any part of the ear including the inner ear, ear canal, middle ear, auditory nerve or auditory nerve pathway to the brain. Other test that may be run to check for hearing loss include audiometry, speech threshold audiometry, discrimination, tympanometry, auditory brain stem response and electrocochleography.
An audiometry measures the hearing loss with an electronic device called an audiometer. This device takes a precise measure by producing sounds in specific pitches or what are called pure tones and specific volumes. Speech and threshold audiometry will measure how loud words must be spoken to be understood, while a discrimination test shows the patients ability to hear the differences between words that sound similar. Tympanometry is a type of audiometry that measures the impedance or resistance to pressure of the middle ear. The auditory brain stem response test helps distinguish between sensory and neural hearing loss and the electrocochleography measures the activity of the auditory nerve and cochlea. Treatment with most hearing loss will depend on the cause. While some causes such as fluid in the ear or ear wax can be eliminated to correct the problem, other causes may be permanent and require a hearing aid for correction.
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