Department of Otolaryngology, Head & Neck Surgery Cochlear Implants Glen T. Porter, MD Arun K. Gadre, MD Department of Otolaryngology, Head & Neck Surgery Galveston, TX

History of Cochlear Implants Volta Djourno and Eyries House, Doyle, Simmons 1972 Single-channel implant 1984 FDA approval 1990’s Beyond

Anatomy Anatomy

Anatomy Scala tympani Scala vestibuli Cochlear duct Basilar membrane Vestibular membrane Tectoral membrane Hair cells (outer/inner) Cochlear nerve fibers

Anatomy-micro

Physiology of Hearing

Anatomy

Sensorineural Hearing Loss Death of hair cells vs. ganglion cells Otte, et al estimated we need 10,000 ganglion cells with 3,000 apically to have good speech discrimination Apical ganglion cells tend to survive better (?acoustic trauma) Central neural system plasticity

Pathologic Anatomy

Anatomy of Sound

Anatomy of Speech Mix of frequencies Speech recognition is “top-down” process Formant frequencies: frequency maximum based on vocal tract F0 is fundamental frequency F1 & F2—contribute to vowel identification F3—l,r (lateral and retroflex glides) F4 & F5—higher frequency speech sounds Some speech based on amplitude—k, f, l, s

Components of Cochlear Implant

Implant Components Microphone External speech processor amplification External speech processor Compression Filtering Shaping Transmitter (outer coil) Receiver Electrode array Neural pathways

Types of Cochlear Implants Single vs. Multiple channels Audio example of how a cochlear implant sounds with varying number of channels Monopolar vs. Bipolar Speech processing strategies Spectral peak (Nucleus) Continuous interleaved sampling (Med-El, Nucleus, Clarion) Advanced combined encoder (Nucleus) Simultaneous analog strategy (Clarion)

Anatomy of a Cochlear Implant

Indication for Cochlear Implant Adults 18 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 suitable No anatomic contraindications Medically not contraindicated

Indications for Cochlear Implantation -- Children 12 months or older Bilateral severe-to-profound sensorineural hearing loss with PTA of 90 dB or greater in better ear No appreciable benefit with hearing aids (parent survey when <5 yo or 30% or less on sentence recognition when >5 yo) Must be able to tolerate wearing hearing aids and show some aided ability Enrolled in aural/oral education program No medical or anatomic contraindications Motivated parents

Contraindications Incomplete hearing loss Neurofibromatosis II, mental retardation, psychosis, organic brain dysfunction, unrealistic expectations Active middle ear disease CT findings of cochlear agenesis (Michel deformity) or small IAC (CN8 atresia) Dysplasia not necessarily a contraindication, but informed consent is a must H/O CWD mastoidectomy Labyrinthitis ossificans—follow scans Advanced otosclerosis

CT Findings

General Workup Audiologic exam with binaural amplification CT scan/MRI of temporal bones Trial of high-powered hearing aids Psychological evaluation Medical evaluation Any necessary tests to discover etiology of hearing loss

Surgical technique

Surgical Technique

Surgical Technique

Postoperative Management Complication rate only 5% Wound infection/breakdown Yu, et al showed good response to Abx, I&D Facial nerve injury/stimulation, CSF leak, Meningitis CDC recommendations Vertigo (Steenerson reported 75%) Device failure—re-implantation usually successful Avoid MRI

Postoperative Rehabilitation Necessary part of implantation Different focus depends on patient’s previous experience with sound Goal is to enable children to be able to learn passively from the environment Program addresses receptive as well as expressive language skills Multidisciplinary, dedicated group necessary

Results of Implantation Wide range of outcomes Improvement is long-term (Waltzman, et al. 5-15 yr f/u) Implantation is cost effective—even in the elderly (Francis, et al) Research indicates recipe for success includes: Short length of time from deafness to implantation (Sharma showed <3.5 years regain normal latencies within 6 mos. After 7 years, little plasticity remains) Experience with language before onset of deafness Implantation before age six for prelingually deafened children (Govaerts, et al showed 90% of children implanted <2yo were integrated into mainstream vs. only 20-30% if implanted after age 4) Aural/oral education Highly motivated patients/parents

A Look to the Future Partial implants with hearing aid Those with residual low-frequency hearing Intraoperative mapping Bilateral implantation One vs. two speech processors Implantation for asymmetric SNHL “Softip” array Minimally invasive implantation