SHS 451 1st EditionExam # 2 Study Guide Chapters 3-5Cochlear Implants – Chapter 3What are the components of a cochlear implant? Cochlear Implant: not an amplifier but a device that bypasses the peripheral auditory system to directly stimulate the auditory nerve. -consists of: - An external worn headset connected to a speech processor- A battery source- Surgically implanted internal receiver stimulator attached to the electrode array that's placed in the cochleaWho is a candidate for a cochlear implant?In the 1980s, only adults with profound postlingual hearing impairment were eligible. Now it has been approved for people over 12 months with bilateral moderate to profound SNHL. EvaluationAAO-HNS recommends testing in quiet at 70 dB SPL using the minimum speech test battery which includes: Hearing in Noise Test (HINT) → 2, 10 sentence lists in quietConsonant-Nucleus-Consonant (CNC) → 1, 50 word listIn 2004, the recommendation was made to reduce the presentation levels to 50 or 60 dB SPL in order to reflect real-life listening. The new minimum speech test batter includes:AZ Bio Sentence TestBanford-Kowal-Bench Speech in Noise TestCNC test presented at 60 dBCriteriaFor adults: < or = to 50% speech recognition in the ear to be implanted when listening at normalconversational levels to sentence material (HINT) in the best aided conditions. (Medicaid has stricter guidelines for payment requiring speech recognition scores of < or = to 50%. The opposite ear must score < or = to 60%. For children: a bilateral profound hearing loss (> or = to 90 dB HL) for 12-24 months of age and severe to profound SNHL (> or = to 70dB HL) in 24 months of age to 18 years with limited benefit from traditional amplification. In older children, the criterion is < or = to 30% word recognition at normal conversational levels in the best aided condition. Formal EvaluationsInclude: Standard audiometric unaided test batteryOtoacoustic Emissions Aided speech perception testing Aided speech reading evaluationsSpeech and language evaluations should be completed on all children and adults with prelingualhearing loss. *MRI's or CT scans are necessary to determine if the device can be implanted*Limitations of Device-Not everyone is able to use the phone even after training-Some individuals may only receive enhancement of their speech reading abilities and awareness of environmental sounds- Adults with prelingual hearing loss have poorer prognosis for success How is a cochlear implant programmed?SurgeryA small area of the mastoid is drilled for placement of the receiver stimulator and the electrode array. The array is threaded through the mastoid and the ME cavity and then inserted in the Scala Tympani of the cochlea through the round window. Insertion depths can range up to 30 mm. After surgery, the patient must wait approximately 2-3 weeks for the external head set andspeech processor to be fitted. It needs to heal before placing the magnet. Hook Up (Initial fitting and programming)-Usually takes 1 to 2 hours-Audiologist must program the speech processor by using a specific manufacturer designed diagnostics programming system interfaced with a personal computer-All current implants have the capability of testing the integrity of the internal device by using a technique called telemetry. Electrode voltages and impedances can be measured when current is supplied through the system. In this manner the audiologist can check the internal device prior to programming the system. If any of the electrodes are found to be out of compliance with standard values, they will not be programmed for use. In some implant centers, telemetry is also completed by the audiologist in the operating room at the time of surgery to ensure proper device functioning before surgical closures. -In order to create the program (MAP), for the speech processor, the audiologist must determine the electrical dynamic range for each electrode used. The programming system delivers an electrical current through the cochlear implant system to each electrode in order to obtain the electrical threshold (C-level) and maximal level of current that is comfortable loud (C-level) measures. T-level or minimum stimulation level is the softest electrical current that produces an auditory sensation by the patient 100% of the time. The C-level is the loudest level that can be listened to comfortably for a long period of time. The speech processor is thenprogrammed or “mapped” using one of the several encoding strategies so that the electrical current delivered to the implant will be within this measured dynamic range between T- and C-levels. -T- and C-levels are easier to obtain on adults and older children with postlingual hearing loss. Techniques for testing the T-levels in young children are similar to testing pure ton hearing thresholds, ranging from observational testing to conditioned play audiometry. Obtaining the C-levels is a challenging task, with the audiologist often relying totally on behavioral observation. -Neural Response Telemetry (Neural Response Imaging, Auditory Response Telemetry): objective techniques that can be used to estimate the dynamic ranges in young children or difficult to test patients. They offer a means of testing the compound action potential of the nerve using 2 of the electrodes in the array as recording electrodes and 2 as stimulating electrodes. With children, audiologists will often evaluation only a limited number of electrodes spaced throughout the electrode array during the initial hookup and either estimate the levels for the other electrodes or only include the tested electrodes in the initial program. -After the levels are established and the MAP is created, the mic is then activated so that the patient is able to hear speech and sounds in the environment. -All current generation systems have multiple memories that allow the audiologist to save more than one MAP in the speech processors. This can be very helpful to the audiologist since, due toacclimatization to sound, the initial levels are often not the final values. Higher current values can be used to make alternative MAPS, which can be saved into the processor's multiple memories so that patients have the option of increasing the power between clinic visits. After their MAP has stabilized, different programs can be designed for various listening situations such as everyday listening, listening in noisy settings, or music. Acclimatization to