Rehabilitation of Hearing Impaired Individuals I. Instrumental devices a. Hearing aids. b . Cochlear implant. II. Training a. Speech therapy and lip reading. b. Auditory training for those using hearing aids and cochlear implants. Rehabilitation of Hearing Impaired Individuals

Since the inner ear functions normally in patients with CHL there is little difficulty in obtaining good results with hearing aids. In SNHL the benefit is not so good as in CHL because the high tones are affected more than the low tones. This mean that the consonant sounds which carry most of the meaning of speech and speech discrimination are less well heard than the vowel sounds. Hearing Aids

Types of hearing aids -Non-electrical: Ear trumpets and speaking tubes. -Electrical: It consists of: (a) microphone, which picks up sounds and converts them into electrical impulses, (b) an amplifier, which magnifies electrical impulses, and (c) a receiver, which converts electrical impulses back to sound. Its of two types:

A. Air conduction hearing aids: The amplified sound is transmitted via the ear canal to the tympanic membrane. 1. Body worn: The microphone and amplifier are worn on the body while receiver is situated at the ear connected to the amplifier by a lead. This type of aid allows high degree of amplification. It is useful in severely deaf persons or children with congenital deafness.

2. Behind the ear (BTE): The microphone receiver and amplifier are all contained in one unit which is worn behind the ear. From the receiver a small plastic pipe carries the sound into the external auditory meatus. It is useful for slight to moderate hearing loss.

3. In the ear (ITE): The entire hearing aid is housed in a mould which can be worn in the ear. 4. In the canal (ITC): The hearing aid is so small that it can be worn in ear canal without projecting into the concha.

Both ITE and ITC are useful for mild to moderate hearing loss Both ITE and ITC are useful for mild to moderate hearing loss. They offer cosmetic advantages but they are expensive. -

5 . Spectacle type: It is modification of BTE and the unit is housed in the auricular part of the spectacle frame. It is useful for persons who need both eye glasses for vision and hearing aids.

B. Bone conduction hearing aids: Instead of a receiver, it has a bone vibrator which fits on the mastoid and directly stimulates the cochlea. It is useful in patients with intractable otitis externa, chronically discharging ear or mastoid cavities or meatal stenosis where ear inserts cannot be worn. Bone anchored hearing aids (BAHA) use a surgically implanted abutment to transmit sound by direct conduction through bone to the cochlea bypassing the external auditory meatus.

BAHA

Indication for hearing aids Hearing aids should be used when deafness become a handicap. This is usual when there is an overall loss for pure tones of more than 30-35 dB in the speech range and in the better ear. Acoustic feed back A whistling sound due to escape of sound from the EAM to the microphone. It occurs if the earpiece is loosely fitting, wax or in otitis media with effusion. Obviously feedback is likely to occur when the microphone is close to the ear as in an ear level aid and less marked in body worn aids.

Is an electronic device that can provide useful hearing and improved communication abilities for persons who have bilateral severe to profound sensorineural hearing loss who cannot benefit from hearing aids. Cochlear Implant

Components of cochlear implant 1. External component: It consists of a microphone, external speech processor and a transmitter. 2. Internal component: It’s surgically implanted and comprises receiver/stimulator package with an electrode array.

The microphone picks up sound and sends it to the speech processor which analyses and code sounds into electrical pulses. These electrical impulses are sent through a transmitting coil (transmitter) to the surgically implanted receiver/stimulator which decodes the signal and transmits it to the electrode array.

The electrode arrays are placed in the basal turn of cochlea The electrode arrays are placed in the basal turn of cochlea. The auditory nerve is thus stimulated and sends these electrical pulses to the brain which are finally interpreted as sound.

Cochlear implant

Neural plasticity Is the ability of CNS to be programmed to learn a task. It seems that excellent speech articulation can only be accomplished if the speech sounds are learnt before the age of 2-3 years. If a person has never utilized the auditory mechanism, the neural plasticity needed to recognize words probably fades completely between the age of 6-8 years.

Candidates for cochlear implant I. Postlingual patients : Onset of deafness has occurred after completion of speech development. They are excellent candidates. II. Prelingual children who are born with profound sensorineural hearing loss who loose hearing before acquiring speech (within the first 2 years of their life). In principle, the younger the age at which they are implanted, the greater the benefit because full average can then be taken of the inherent “plasticity” of the auditory CNS.  

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