Cochlear Implants in Developing Countries - Vula - University of ...

acoustic input into a usable electricaldynamic range for each electrode which isstimulated.The audiologist who does the programming/MAPpingis responsible for maintenanceand programming of the CI, includinginitial stimulation and regular followupprogramming sessions. The audiologistobtains 2 psychophysical measures i.e.elec-trical thresholds (T-levels) andcomfort levels (C-levels), to create aprogram (MAP).An appropriate encoding strategy as wellas a stimulation mode should be selectedfor each patient. Encoding strategy is themeans by which an implant translates theincoming acoustic signal into patterns ofelectrical pulses which in turn stimulate theauditory nerve fibres. Stimulation moderefers to the flow of electric current, that is,the location of the indifferent (reference)electrode relative to the active (stimulated)electrode. A combination of objective andbehavioural programming techniques areutilised to establish an appropriate MAPfor each CI recipient.Bilateral CIsIn the developed world, children andgrowing number of post-lingual deaf adultpatients are commonly implanted. Implantingbilateral CIs means that 2 separateinternal and external hardware systems areimplanted either concurrently or sequentially.The speech processors do not communicatewith one another and programmingMAPs are done independently foreach processor.Advantages of bilateral CIs include:Improved sound localisationImproved speech understanding inquiet conditions as well as with backgroundnoiseBoth auditory pathways are stimulatedwhich ensures that the better performingear has been implanted (since it isdifficult to determine pre-operativelywhich ear will perform better with aCI)The 2 nd CI acts as a reserve should oneof the implants failEnsures binaural hearing and thusassists in a young child’s developmentof central auditory processing skillsThe ideal bilateral adult CI candidate haspost-lingual hearing loss and a relativelyshort duration of profound hearing loss(

Establishing a CI Programme in aDeveloping CountryAudiologists are key members of a unitstarting to do CIs in a developing country.Limited audiological service and insufficientrehabilitative resources are thereforethe greatest challenges. Audiologists (orspecially trained hearing health providers)should be well versed with assessinghearing in young children as well as inseverely hearing impaired adults. Detailedknowledge of anatomy, physiology, electricalstimulation, CI technology andrehabilitation is required, and the audiologistmust be educated and be familiarwith the specific CI system to be used.Intensive, hands-on training with regard toprogramming software, intra-operativemonitoring, programming (MAPping) andtrouble-shooting are essential.An ear surgeon with knowledge ofaudiology has to be part of the CI teamfrom the beginning. He/she should befamiliar with middle ear and mastoidsurgery; surgery for CI in itself is not verycomplicated and in most instances isperformed on ears with normal grossanatomy. Multiple CI courses for surgeonsare available worldwide 5 .The major CI brands are the predominantlyused in the developing world, mainlybecause of their extensive experience andthe support and services that the providersoffer. There is an ongoing debate as towhether a more affordable CI would bemore appropriate for low-income countriesas it might be of lower quality and notas reliable. However, the prices of devicesand accessories will have to be reduced tomake CIs accessible to patients in thedeveloping world.ConclusionsCIs have been a major advance in thetreatment of deafness. Despite the remarkableoutcomes of CIs in adult and paediatricpatients, its availability as well as therequired specialised services remainlimited in the developing world.References1. Muller AMU, Wagenfeld DJH.Cochlear Implants in South Africa.ENT News, 2003;12(2):57-622. Sharma A, Dorman MF, Spahr AJ. Asensitive period for the development ofthe central auditory system in childrenwith cochlear implants: Implicationsfor age of implantation. Ear Hear2002;23(6):532-93. Muller AMU, Wagenfeld DJH.Paediatric cochlear implantation. CME:SA Journal of CPD: Community ENT,2003;21(11):628-324. Peters BR, Litovsky R, Parkinson A,Lake J. Importance of age and postimplantationexperience in speechperception measures in children withsequential bilateral cochlear implants. JOtol Neurotol 2007;28(5):649-575. http://www.entandaudiologynews.com/diary/AuthorTalita le RouxLecturer in AudiologyAudiologist: UP Cochlear Implant UnitDepartment of Communication PathologyUniversity of PretoriaSouth Africatalita.leroux@up.ac.zaAuthor and EditorClaude Laurent, MD, PhDProfessor in ENTENT Unit, Department of Clinical ScienceUniversity of UmeåUmeå, Swedenclaude.laurent@ent.umu.se5

EditorsDe Wet Swanepoel PhDAssociate ProfessorDepartment of Communication PathologyUniversity of PretoriaPretoria, South Africadewet.swanepoel@up.ac.zaJohan Fagan MBChB, FCORL, MMedProfessor and ChairmanDivision of OtolaryngologyUniversity of Cape TownCape Town, South Africajohannes.fagan@uct.ac.zaOPEN ACCESS GUIDE TOAUDIOLOGY & HEARING AIDSFOR OTOLARYNGOLOGISTShttp://www.entdev.uct.ac.zaThe Open Access Atlas of Otolaryngology,Head & Neck Operative Surgery by JohanFagan (Editor) johannes.fagan@uct.ac.za islicensed under a Creative CommonsAttribution - Non-Commercial 3.0 UnportedLicense6