Cochlear Implantation and Other Implantable Technology

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Cochlear Implantation and Other Implantable Technology

Otology/Audiology
Author Credentials 

Cameron Wick, MD
Assistant Professor
Otolaryngology – Head and Neck Surgery
Washington University School of Medicine
St. Louis, MO

 

Module Summary

Cochlear implants represent the most successful neural prosthesis to date. Their development is a testament to courageous scientists, surgeons, audiologists, and patients who have pushed the technology forward. The devices work by stimulating spiral ganglion neurons located within the cochlea’s modiolus. A solid understanding of the temporal bone, facial nerve, and cochlea anatomy will optimize surgical placement of the electrode and limit surgical complications. The success of cochlear implants has led to expanded candidacy criteria and even implantation of some non-traditional candidates (electroacoustic, single-sided deafness, etc.). Ultimate cochlear implant performance depends on various patient, device, and surgical factors. Device complications are rare but when they occur they need to be reported in a standardized fashion.

Module Learning Objectives 
  1. Describe the embryology and anatomy of the cochlea.
  2. Explain the indications and contraindications of traditional cochlear implant candidates. Also, recognize some of the non-traditional candidates.
  3. Distinguish how a cochlear implant evaluation differs from a standard audiogram. 
  4. Explain the basics of how the cochlear implant device works.
  5. Recognize some of the variables responsible for variations in cochlear implant performance. 

 

Embryology

Learning Objectives 
  1. The external and middle ears develop from the 1st and 2nd branchial arches, while the inner ear develops from the otic placode. Describe how the development of the inner ear differs from the external and middle ears.
  2. Appreciate how abnormalities in cochlear development can affect cochlear implant performance.

 

References 
  1. Fuchs JC, Tucker AS. Development and integration of the ear. Curr Top Dev Biol. 2015;115:213-232.
  2. Buchman CA, Copeland BJ, Yu KK, Brown CJ, Carrasco VN, Pillsbury HC 3rd. Cochlear implantation in children with congenital inner ear malformations. Laryngoscope. 2004 Feb;114(2):309-16.

 

Anatomy

Learning Objectives 
  1. Ideal cochlear implant electrode placement is within the scala tympani. Identify the different compartments (scala) within the cochlea and where the spiral ganglion neurons reside. 
References 
  1. Runge CL, Friedland DR. Anatomy of the auditory system. In: Flint PW, et al. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia: Elsevier/Saunders; 2015: p.1987-1993.

Pathogenesis

Learning Objectives 
  • Refer to Otology/Audiology unit on “Sensorineural Hearing Loss”
  • Refer to Pediatric unit on “Pediatric Hearing Loss”

 

Basic Science

Learning Objectives 
  1. Many scientists, surgeons, and patients have contributed to the success of cochlear implants. Dr. William House’s ground-breaking work cannot be overstated. Three other influential figures, Graeme Clark, Ingeborg Hochmair, and Blake Wilson, were honored in 2013 with the Lasker-Debakey Clinical Medical Research Award. Review a summary of their pioneering work in these references. 
References 
  1. Clark GM. The multi-channel cochlear implant: multi-disciplinary development of electrical stimulation of the cochlea and the resulting clinical benefit. Hear Res. 2015;322:4-13.
  2. Hochmair I, Hochmair E, Nopp P, Waller M, Jolly C. Deep electrode insertion and sound coding in cochlear implants. Hear Res. 2015;322:14-23.
  3. Wilson BS. Getting a decent (but sparse) signal to the brain for users of cochlear implants. Hear Res. 2015;322:24-38

 

Incidence

Learning Objectives 
  1. Sensorineural hearing loss is common, especially in older adults. In 2014, approximately 37.5 million Americans (15% of the U.S. population) reported difficulty hearing. Despite the success of cochlear implants market penetration remains well below 10% for the eligible adult candidates. Explain current cochlear implant referral patterns and some of the barriers for delivering cochlear implant technology.
References 
  1. Holder JT, Reynolds, Sunderhaus LW, Gifford RH. Current profile of adults presenting for preoperative cochlear implant evaluation. Trends Hear. 2018;22: 2331216518755288.

Genetics

Learning Objectives 
  • Refer to Pediatric unit on "Pediatric Hearing Loss"

Patient Evaluation

Learning Objectives 
  1. Summarize the common word and sentence tests used to determine cochlear implantation candidacy. 
  2. Recognize how cochlear implant candidacy has evolved since its initial FDA approval and current trends for candidacy testing.
  3. Gain awareness of non-traditional candidates, such as electroacoustic/hybrid criteria and asymmetric or single-sided deafness candidates.

 

References 
  1. Wackym PA, Tran A. Cochlear implantation: Patient evaluation and device selection. Flint PW, et al. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia: Elsevier/Saunders; 2015: p  2428-2443.
  2. Sladen DP, Gifford RH, Haynes D, et al. Evaluation of a revised indication for determining adult cochlear implant candidacy. Laryngoscope. 2017;127(10):2368-237.4
  3. Carlson ML, Sladen DP, Haynes DS, et al. Evidence for the expansion of pediatric cochlear implant candidacy. Otol Neurotol. 2015;36(1):43-50.
  4. Carlson ML, Sladen DP, Gurgel RK, Tombers NM, Lohse CM, Driscoll CL. Survey of the American Neurotology Society on cochlear implantation: Part 1, candidacy assessment and expanding indications. Otol Neurotol. 2018;39(1):e12-e19.

 

Imaging

Learning Objectives 
  1. Imaging is a critical component of the cochlear implant evaluation but there is no consensus on whether computed tomography (CT), magnetic resonance imaging (MRI), or both are warranted. List the medical and surgical considerations during cochlear implant evaluation.
References 
  1. Balkany TJ, Brown KD. Medical and surgical considerations in cochlear implantation. In: Flint PW, et al. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia: Elsevier/Saunders; 2015: p. 2444-2454.

Treatment

Learning Objectives 
  1. There are many different metrics to measure cochlear implant outcomes. Explain some of the classic variables that affect implant performance. Also, recognize how implants affect quality of life.
References 
  1. Wanna GB, Noble JH, Carlson ML, et al. Impact of electrode design and surgical approach on scalar location and cochlear implant outcomes. Laryngoscope. 2014;124(Suppl 6):S1-S7.
  2. Holden LK, Finely CC, Firszt JB, et al. Factors affecting open-set word recognition in adults with cochlear implants. Ear Hear. 2013;43(3):342-360.
  3. Blamey P, Artieres F, Baskent D, et al. Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants: an update with 2251 patients. Audio Neurootol. 2013:18(1)36-47.
  4. Vila PM, Lieu JE, Hullar TE, Buchman CA. Developing quality measures for adult cochlear implant centers: preliminary findings. Otolaryngol Head Neck Surg. 2016:155(5)748-752.
  5. McRackan TR, Bauschard M, Hatch JL, Franko-Tobin E, Droghini HR, Nguyen SA, Dubno JR. Meta-analysis of quality-of-life improvement after cochlear implantation and associations with speech recognition abilities. Laryngoscope. 2018:128(4):982-990.

 

Pharmacology

Learning Objectives 
  1. Local drug delivery into the inner ear remains an active area of cochlear implant research. Review the current techniques of extracochlear drug administration and learn about the potential for intracochlear gene therapy or drug-eluting electrode designs.
References 
  1. Plonthke SK, Götze G, Rahne T, Liebau A. Intracochlear drug delivery in combination with cochlear implants: current aspects. HNO. 2017;65(Suppl 1):19-28.

Surgical Therapies

Learning Objectives 
  1. Common approaches for cochlear implant electrode insertion include: round window, extended round window, and cochleostomy. Summarize and explain the differences between these approaches and the optimal vector for each. 
  2. Uncommon approaches for cochlear implant electrode insertion include: scala vestibuli cochleostomy, middle turn cochleostomy, and drill-out. Gain a general awareness of these different approaches and when they might need to be used. 

 

References 
  1. Adunka OF, Radeloff A, Gstoettner WK, Pillsbury HC, Buchman CA. Scala tympani cochleostomy II: topography and histology. Laryngoscope. 2007;117(12):2195-2200.
  2. Iseli C, Adunka OF, Buchman CA. Scala tympani cochleostomy survey: a follow-up study. Laryngoscope. 2014;124(8):1928-1931.
  3. Roland PS, Wright CG, Isaacson B. Cochlear implant electrode insertion: the round window revisted. Laryngoscope. 2007;117(8):1397-1402.
  4. Meshik X, Holden TA, Chole RA, Hullar TE. Optimal cochlear implant insertion vectors. Otol Neurotol. 2010;31(1):58-63
  5. Isaacson B, Roland PS, Wright CG. Anatomy of the middle-turn cochleostomy. Laryngoscope. 2008;118(12):2200-2204.

 

Rehabilitation

Learning Objectives 
  1. Cochlear implant rehabilitation requires using and adjusting to the device. Children and adults may have different needs to facilitate this goal. Identify about some of the education and rehabilitation strategies used to improve cochlear implant performance.
References 
  1. Moog JS, Geers AE. Early education placement and later language outcomes for children with cochlear implants. Otol Neurotol. 2010;31(8):1315-1319.
  2. Harris MS, Capretta NR, Henning SC, Feeney L, Pitt MA, Moberly AC. Postoperative rehabilitation strategies used by adults with cochlear implants: A pilot study. Laryngoscope Investig Otolaryngol. 2016;1(3):42-48.
  3. Limb CJ, Francis HW, Niparko JK. Cochlear implantation: Results, outcomes, rehabilitation, and education. In: Flint PW, et al. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia: Elsevier/Saunders; 2015: p. 2455-2471.

 

Case Studies

  1. A 65-year-old female complains of poor ability to understand speech despite using appropriately fit hearing aids. What are your indications to obtain a cochlear implant evaluation or initiate a cochlear implant referral? 
  2. A 56-year-old male is a cochlear implant candidate and wants to know more about how he will do with the device. What are some of the patient, device, and surgical factors that will impact his performance?

 

Complications

Learning Objectives 
  1. Cochlear implants are very reliable, however surgical complications, device failures, and long-term wound issues may arise. Understand the difference between a hard and a soft device failure.  Recognize the most common reasons for short- and long-term wound complications.
  2. Children with inner ear malformations have a greater risk of meningitis. People with cochlear implants are also at an increased risk of developing meningitis, most commonly from Streptococcus pneumoniae. For this reason, the Center for Disease Control and Prevention (CDC) recommends vaccination against meningitis prior to cochlear implantation. Review the CDC guidelines for pediatric and adult vaccinations prior to cochlear implant surgery. 

 

References 
  1. Balkany TJ, Hodges AV, Buchman CA, et al. Cochlear implant soft failures consensus development conference statement. Cochlear Implants Int. 2005;6(3)105-122.
  2. Zeitler DM, Budenz CL, Roland JT Jr. Revision cochlear implantation. Curr Opin Otolaryngol Head Neck Surg. 2009;17(5): 334–338.
  3. Walgama ES, Isaacson B, Kutz JW Jr, Roland PS. Management of electrode exposure after cochlear implantation. Otol Neurotol. 2012;33(7):1197-1200.
  4. Carlson ML, Neff BA, Link MJ, et al. Magnetic resonance imaging with cochlear implant magnet in place: safety and imaging quality. Otol Neurotol. 2015;36(6):965-971.
  5. Centers for Disease Control and Prevention (CDC). Use of Vaccines to Prevent Meningitis in Persons with Cochlear Implants. Available: https://www.cdc.gov/vaccines/vpd/mening/hcp/dis-cochlear-gen.html

 

Review

Review Questions 
  1. What does the inner ear derive from and how is this different from the external and middle ear structures?
  2. What clinical and audiometric findings warrant a cochlear implant evaluation or referral to a cochlear implant center?
  3. What are the current FDA guidelines for adult cochlear implantation candidacy? What about for children? 
  4. List some of the contraindications of cochlear implantation?
  5. Describe the difference between a round window, extended round window, and cochleostomy approach?
  6. What patient factors, device factors, and surgical factors affect cochlear implant performance?
  7. Explain the difference between a hard and soft device failure?

 

Resources 

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  1. Annual Meeting Webcast (AMW):