Introduction to Hearing Loss

	*Conductive*	*Sensory Neural*
1. Site	Outer or middle ear.	Inner ear or cochlea and the nerve pathways to auditory centres in the brain.
2. Deafness because	Vibrations do not reach the inner ear or arrive there attenuated.	Vibrations are not registered by nerve cells in the inner ear because they are damaged, or have never developed.
3. Reasons for deafness	Outer ear - obstruction such as impacted ear wax. Middle ear - vibration of the eardrum or middle ear bones is interrupted by: fluid build up in the middle ear, ear infections, or breakage in the ossicular chain	1. Heredity (or genetic factors) 2. Rubella or German measles. 3. Diseases of perinatal period. 4. Diseases of later childhood, for example, meningitis. 5. Noise induced hearing loss.

4. Amenable to treatment	Medical and surgical procedures can be effective.	There is not a cure for sensory neural hearing loss, however a cochlear implant may be an option for a deaf person.
5. Characteristics of hearing loss	Loss for low and high pitch sounds is similar. Usually a mild to moderate degree of hearing loss.	Usually the loss of hearing for high pitches is greater - often much greater than for low pitch sounds. Hearing loss can range from mild to profound.
6. How speech is heard	Muffling in the perception of speech. Usually there is minimal distortion in the perception of the speech signal. Hearing aids sound very clear.	Distortion in the perception of speech. Vowels may be heard relatively well; consonants are often distorted, if heard at all. Hearing aids sound somewhat distorted, but are necessary.

Summarized By Thirayost Nimmanon

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