Cochlear Implant

Cochlear Implant

The Fundamental Concept of Cochlear ImplantTo bypass the damaged hair cells.

History: Old generation: Sound awareness only New generation: Improved communication abilities (auditory cues with lip reading, open set speech) Since 1972 more than 16 different cochlear implants 1984 FDA approval for adults 1990 children approval

AnatomyAnatomy

AnatomyScala tympaniScala vestibuliCochlear ductBasilar membraneVestibular membraneTectorial membraneHair cells (outer/inner)Cochlear nerve fibers

Physiology of Hearing

Anatomy-micro

Anatomy

Sensorineural Hearing LossDeath of hair cells vs. ganglion cellsOtte, et al estimated we need 10,000 ganglion cells with 3,000 apically to have good speech discriminationApical ganglion cells tend to survive better

Pathologic Anatomy

Structure of Cochlear ImplantExternal componentsInternal components

Components of Cochlear Implant

Anatomy of a Cochlear Implant

How does it work?

Neural Responses to SoundTemporal coding: Provide information about timing cues (rhythm and intonation.Place coding: Rely on the tonotopic organization of a neural fibers.Provide information about quality (timber of a speech signal sharp to dull)

Site of StimulationExtracochlearIntracochlearRetrocochlear (lateral recess of the fourth ventricle over the cochlear nuclei.

Number of ChannelsSingle channel no place codingMulti channel

Electrode Design1. Single electrode2. Multielectrode

Indication for Cochlear ImplantAdults18 years old and older (no limitation by age)Bilateral severe-to-profound sensorineural hearing loss (70 dB hearing loss or greater with little or no benefit from hearing aids for 6 months)Psychologically suitableNo anatomic contraindicationsMedically not contraindicated

Indications for Cochlear Implantation -- Children12 months or olderBilateral severe-to-profound sensorineural hearing loss with PTA of 90 dB or greater in better earNo appreciable benefit with hearing aids (parent survey when 5 yo)Must be able to tolerate wearing hearing aids and show some aided abilityEnrolled in aural/oral education programNo medical or anatomic contraindicationsMotivated parents

Factors Affecting Patient SelectionOnset of deafness (congenital or adventitious)Year of deafnessLength of sensory deprivation (i.e. no hearing aids)Socioeconomic factorsEducational levelIndividual ability to use minimal cuesGeneral health

Factors Affecting Pt. (cont.)PersonalityWillingness to participate in rehabilitation programLanguage skillsAppropriate expectationsDesire to communicate in a hearing societyPsychological stabilityCochlear patency

Audiologic EvaluationPure tone audiometry under headphonesAudiometry with a hearing aid in a monitored free field Immittance testingSpeech recognition testingOAE

Audiologic Evaluation (cont.)Environmental sounds (closed and open set)Speech reading (lip reading) ability Electrical response audiometryAuditory discriminationTranstympanic electrical stimulation (promontory or round window test)

Medical EvaluationClinical history and initial interviewPreliminary examinationComplete medical and neurologic examinationCochelar imaging using computed tomography (CT or magnetic resonance imaging (MRI)Vestibular examination (electronystagmography)EKGPsychologic or psychiatric assessment or bothVision testingAssessment for anesthetic procedures

CT Findings

ContraindicationsIncomplete hearing lossNeurofibromatosis II, mental retardation, psychosis, organic brain dysfunction, unrealistic expectationsActive middle ear diseaseCT findings of cochlear agenesis (Michel deformity) or narrow IAC (CN8 atresia)Dysplasia not necessarily a contraindication, but informed consent is necessaryH/O CWD mastoidectomyLabyrinthitis ossificansfollow scansAdvanced otosclerosis

Rehabilitation1-6-12 programBinaural Hearing Aid

Surgical ProcedureAll electrode insertions are carried out through the facial recess approach. Various incision designs are used to allow wide exposure of the mastoid and squamous portions of the temporal bone. The temporalis muscle and periosteum are widely stripped to accommodate a table for the pedestal of the Ineraid device or the receiver-stimulator of the other devices. The mastoidectomy is not widely saucerized, but instead overhanging ledges are purposefully maintained. Care must be exercised so as not to damage the fibrous annulus during the facial recess approach..

Surgical Technique

Complications:A. Intraoperative

1. Intraoperative cannot be placed appropriately. 2. Insertion trauma 3. Gusher

Complications (cont.):B. Postoperative 1. Postauricular flap edema, necrosis or separation 2. Facial paralysis 3. Transient vertigo is more likely to occur on a totally nonfunctioning vestibular system. 4. Pain is usually associated with stimulation of Jacobsons nerve, the tympanic branch of the glossopharyngeal nerve. 5.Facial nerve stimulation 6. Meningitis 7. Device extrusion

Rehabilitation Tuning or mapping of the external processor to meet individual auditory requirements after 3 - 4 weeks postop.

Rehabilitation

Rehabilitation

Rehabilitation

Rehabilitation

Rehabilitation

Rehabilitation

Rehabilitation

Pediatric ImplantationFive years after approval was given for adult implanta-tion by FDA, approval of cochlear implants for use in patients ages 2 to 17 years was granted. The major concerns regarding implantation in children included difficulty in evaluating the young childs hearing impairment, assessing the performance and effect of implantation on the childs development compared with traditional types of training, the risks of implantation (both intraoperative and long term), the effects of implantation on the auditory system, and the challenges of effectively programming such sophisticated devices in children.

New ConceptsAgeABI Binaural CI

Auditory Brain Stem