Detail physical, otologicial, nose and throat
C. Preoperative Investigations
-Verifies the degree of HL
-Ensure that the acoustic nerve and brainstem auditory pathway are sufficiently preserved to support CI
– Brain stem auditory evoked potentials (BAEP)
– Electrocochleography (ECochG)
– Promontory stimulation testing
3. Vestibular tests:
4. Radiological tests
5. The Final Assessment Meeting
The controversy over cochlear implants has many sides.
Being deaf is traditionally defined as an inability to hear. For many people, being deaf is considered to be quite challenging and in fact it is even classified as a disability. For others especially those who were born without the ability to hear it is just another type of existence. Most people who are part of deaf consider cochlear implant surgery to be quite unacceptable and is considered disrespectful and insulting, since the medical community views deafness as a handicap which must be treated or corrected. They view being deaf is not a handicap person but a shared experience which gives the deaf community its unique cultural identity. They feel it as “a minority threatened by the hearing majority”.
The deaf community feels that their way of life is fully functional.
Mary Koch, who started the children’s re-habitation program at Johns Hopkins’ Listening Center, says the medical world were split at the outset.
“The (deaf community’s)perception is that there nothing wrong. There nothing that need to be fixed. Our perception is, there is something that need to be fixed . From the very foundation, we are diverging in our perspective, ” Koch says.
“Its difficult to except something that would take someones entire culture into question.”
They feel it is a form of ethnic “genocide.”
Deaf culture activists have two main problems with the implant.
One is that implanting children at the very young age encourages them to be oral and places emphasis on speech and lip reading. Deaf activists feel not only that this is not only natural or comfortable way of communication for deaf people, but that making children”hearing ” by implanting them denies them ASL and the Deaf experience.
Deaf people who have implants are not seen as a Deaf but are label either a as “hard of hearing,” “hearing-deafies” or “hearing wanables”(Arana-Ward A01).In fact deaf activist argue, the CI will prevent the deaf person from functioning in either the deaf and hearing worlds, “since he will never be accepted as a full member” of either group (Arana-Ward A01).
Implantation in older children and adolescents
The ideal age for in congenitally deaf children has been discussed. The current recommendation is around or just before the age of two years. Several studied has examined the benefits of implantation in older children and adults.
Graham concluded that children <2 years should not be implanted and there should not be upper age limit say 6 or 7 for implanting prelingually deaf child.
Waltzman et al examined the outcomes in 35 congenitally deaf children who received the implant after the age of 8 years and 14 congenitally deaf adults. The result indicated that there was improvement in open-set speech perception in children. Adults demonstrated improvement in mean scores for word and sentence recognition, although the improvement was not as significant as in the children implanted at a younger age. Result were adversely influenced by increasing duration of deafness and older age at time of implantation.
Bilateral cochlear implantation
In the last few years, experience has growth with bilateral implantation and studies in adults report the benefits binaural hearing sound should provide, including sound localization and enhanced speech recognition in background noise.Muller et al reported a study of nine bilaterally implanted adult patients tested for speech understanding in quite and in noise. They were tested in three situations, left implant only, right implant only and both implants activated . The speech discrimination tests included monosyllables in quite and sentences in noise. Result indicated higher speech score for all subjects with bilateral stimulation. This has encourage bilateral implantation in children and prelimanary results indicate that outcome measure by auditory perception and speech intelligibility are improved. Bilateral implantation will require further longitudinal evaluation of significant numbers of children in order to confirm these reports indicating that additional benefits occured from the second implant.
Post-lingual and Pre-lingual candidate:
Postlingual candidate has complete development of speech. So they report hearing sensation post implantation and hence considered excellent candidate previously. But later there was the issue about the plasticity and even the postlingual should be implanted before the age of 8 years. And the duration of deafness is inversely related to success.
There was a dilemma whether or not prelingual deaf candidate were to be implanted.These candidate are deaf before development of speech. They were found to be confused of the resulting sensation post implantation and thus were disappointing. But recently the age between 1-2 year of life is considered best time of implantation.
Which ear is to be implanted?
This aspect of CI ha remained very controversial. Formerly it was believed that the ear with residual hearing and functioning cochlear hair cell is to be preserved. It was suggested to avoid an ear which has sufficient residual hearing and functioning cochlear hair cells to gain benefits from conventional acoustic amplification.
Now it is preferred to implant the ear which has functional hearing cells compared to which don’t and provided both ear is dead, an ear with lesser duration of deafness is a choice of implantation.
CI in children with meningitis
CI in children with pro fund deafness due to meningitis is ossification is identified. They are advised early implantation to improve the chances of satisfactory implantation of multichannel electrode array. House carried out the surgery sooner than 4 months after meningitis.
While there are cases reported who recovered 6 months (Balkany et al), 25 months (Brookhouse) and 14 months (McCormica) post meningitis.
Thus it is controversial whether top wait for recovery or implant. However, they recommend a period of six months wait post meningitis should be enough to detect most cases of spontaneous recovery.
Miscellaneous Note From CI:
MRI following cochlear implantation
The presence of the magnet in current implant systems has led to MRI being contradicted in implanted patients. The device have are movable magnet, a small incision over the posterior half of the receiver/stimulator package will allow the implanted magnet to be removed to enable MRI to be performed. This requires a small surgical procedure with the risk of introducing infection. A recent study shows that it is possible to perform an MRI scan provided the scanner is equipped with a 1-Tesla magnet.
PRE-REQUISITES FOR CI:
Hearing loss should be profound or total or bilateral SNHL.
Unaided HL>=95 dB Hz showing no significant usable hearing
Aided>= 60dB Hz IN 500 Hz, 1,2,3,4 KHz
There must be clear lack of hearing aid benefit over a period of months. It is essential that any candidate considered for possible CI should have had an adequate trial of appropriate conventional amplification for minimum of 6 months.
Speech and language through hearing aid or tactile aid
If he demonstrate significant open set word recognition or significant above chance performance or close set word identification tests, do not consider him as implant candidate.
There should be any conductive component of HL. If it is present, it should be eliminated and further assessment should be carried out
Central auditory pathway must be functioning.
Extent, timing and cause of the hearing loss.
Whether a hearing aid has been useful
How the patient communicates
Is there any usable speech?
Any major health problems
Any evidence of development delay
Past otological history: ear infections, ear surgery. otitis media with effusion
Family history: how does the family communicate?'
Social history: does the patient understand and want the implant?
Appearance including congenitial stigmata
Any abnormal behavior
Status of the meatus, tympanic membrane and middle ear, presence of a mastoid cavity or atticotomy
Nose and throat, and general examination
Audiology: adults, pure tone audiogram, special speech tests to measure discrimination
Electrocochleography, steady state potential testing, brain stem auditory potentials
Vestibular tests: caloric testing in adults
Radiological tests: high quality CT scans (MRI, PET) chest X-ray
Teacher of the deaf
Otologists medical and surgical care
Patient support group
Radiologist and staff
|Children||As for adults, plus the following:
audiologists need paediatric experience
Teacher of the deaf (habilitationist)
|Tonotopic fashion +||Allows to acess apical region of cochlea which is not accessible from the around window|
|Electrode are threaded via round window and not further deep than 25mm||Speech information coded near the apex and it is also the region in which nerve survival tends to be best.|