Conductive Hearing Loss

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Conductive Hearing Loss

Otology/Audiology
Author Credentials 

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

 

Module Summary

The external and middle ears are designed to amplify sound energy. When problems occur in those spaces it results in a conductive hearing loss. Understanding the anatomy and physiology of the external auditory canal, tympanic membrane, and ossicles are critical for an accurate conductive hearing loss diagnosis. The rehabilitation options depend on addressing the underlying pathology and trying to restore elements that can efficiently conduct sound energy. 

Module Learning Objectives 
  1. Review how sound is transmitted and amplified through the outer and middle ear spaces.   
  2. Identify a conductive or mixed hearing loss on an audiogram.
  3. Recognize the multiple pathologies that can create a conductive hearing loss.
  4. Summarize the different hearing rehabilitation options as well as their inherent advantages and disadvantages.

 

Embryology

Learning Objectives 
  1. The external and middle ears develop from the 1st and 2nd branchial arches as well as the 1st branchial cleft and 1st pharyngeal pouch. Explain the derivates from these primitive structures.  
  2. Recognize that the development of the external and middle ears is different than the stapes footplate and inner ear.

 

References 
  1. Fuchs JC, Tucker AS. Development and integration of the ear. Curr Top Dev Biol. 2015;115:213-232

Anatomy

Learning Objectives 
  1. Recognize the shape, articulating surfaces, and support structures for the malleus, incus, and stapes.
  2. Define the different middle ear spaces, including the protympanum, mesotympanum, epitympanum, retrotympanum, and hypotympanum. Understand the important structures within each space.
  3. There are different theories on how the middle ear and mastoid spaces ventilate from the Eustachian tube. Describe the epitympanic diaphragm and how variations in the tensor fold can alter ventilation pathways into the epitympanum. 

 

References 
  1. Tarabichi M, Marchioni D, Presutti L, Nogueira JF, Pothier D. Endoscopic transcanal ear anatomy and dissection. Otolaryngol Clin N Am. 2013;46:131-154
  2. Marchioni D, Piccinini A, Alicandri-Ciufelli M, Presutti L. Endoscopic anatomy and ventilation of the epitympanum. Otolaryngol Clin N Am. 2013;46:165-178

Pathogenesis

Learning Objectives 
  1. Explain that conductive hearing loss can occur from a variety of pathologies including obstruction of the external auditory canal, otitis externa, tympanic membrane perforations/pathology, otitis media, and disruption of the ossicular chain.
  2. Familiarize yourself with some of the common underlying pathologies like tympanic membrane perforation, chronic otitis media with effusion, and otosclerosis.
  3. Recognize less common causes of conductive hearing loss including those conditions, like superior semicircular canal dehiscence and enlarged vestibular aqueduct, that create a third window phenomenon or “pseudoconductive” hearing loss.    

 

References 
  1. Merchant SN, Ravicz ME, Puria S, Voss SE, Whittemore KR Jr, Peake WT, Rosowski JJ. Analysis of middle ear mechanics and application to diseased and reconstructed ears. Am J Otol. 1997;18(2):139-154
  2. Rosenfeld RM, Shin JJ, Schwartz SR, et al. Clinical practice guideline: Otitis media with effusion (update). Otolaryngol Head Neck Surg. 2016;154(1 Suppl):S1-S41
  3. Quesnel AM, Ishai R, McKenna MJ. Otosclerosis temporal bone pathology. Otolaryngol Clin N Am. 2018;51:291-303
  4. Merchant SN, Rosowski JJ. Conductive hearing loss caused by third-window lesions of the inner ear. Otol Neurotol. 2008;29(3):282-289

 

Basic Science

Learning Objectives 
  1. Summarize concepts of ossicular coupling and acoustic coupling.
  2. Sound energy gets transmitted from the air-filled middle ear space into the fluid-filled inner ear through the process of impedance matching. Describe how elements of area ratio and lever ratio contribute to impedance matching and sound amplification.

 

References 
  1. Merchant SN, Ravicz ME, Puria S, Voss SE, Whittemore KR Jr, Peake WT, Rosowski JJ. Analysis of middle ear mechanics and application to diseased and reconstructed ears. Am J Otol. 1997;18(2):139-154
  2. Goode RL, Killion M, Nakamura K, Nishihara S. New knowledge about the function of the human middle ear: development of an improved analog model. Am J Otol. 1994:15(2);145-154

Genetics

Learning Objectives 
  1. Cite that many conditions related to conductive hearing loss do not have a well-defined genetic component. 
  2. Otosclerosis is complex disorder with both genetic and environmental factors. Recognize the classic teaching of otosclerosis as an autosomal dominant disorder with incomplete penetrance and acknowledge newer insights into its genetic complexity. 

 

References 
  1. Babcock TA, Liu XZ. Otosclerosis: from genetics to molecular biology. Otolaryngol Clin North Am. 2018;51(2):305-318

Patient Evaluation

Learning Objectives 
  1. Cite that otoscopy and/or otomicroscopy are critical for evaluation of the tympanic membrane and middle ear space.
  2. Review how tuning fork exams, Weber and Rinne, can predict and/or confirm audiometric findings.  

 

References 
  1. Lee DH. How to improve the accuracy of diagnosing otitis media with effusion in a pediatric population. Int J Pediatr Otorhinolaryngol. 2010;74(2):151-153
  2. Foster MF, Backous DD. Clinical evaluation of a patient with otosclerosis. Otolaryngol Clin North Am. 2018;51(2):319-326

 

Measurement of Functional Status

Learning Objectives 
  1. The audiogram is a critical component of evaluating a patient with hearing loss. Describe how to interpret the audiogram to identify a conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.
  2. Identify what information acoustic immittances and acoustic reflexes can provide on the status of the tympanic membrane, ossicular chain, and brainstem.

 

References 
  1. Kileny PR, Zwolan TA. “Diagnostic audiology.” In: Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Elsevier/Saunders; 2015:2051-2071 

Imaging

Learning Objectives 
  1. Otosclerosis changes the density of the otic capsule bone. Identify its most common location at the fissula ante fenestram versus more advanced disease associated with cochlear otosclerosis. 
References 
  1. Purohit B, Hermans R, Op de beeck K. Imaging in otosclerosis: A pictorial review. Insights Imaging. 2014;5:245-252
  2. Subramanian M, Chawla A, Chokkappan K, Lim T, Shenoy JN, Chin Guan Peh W. High-Resolution Computed Tomography Imaging in Conductive Hearing Loss: What to Look for? Curr Probl Diagn Radiol. 2018;47(2):119-124

Treatment

Learning Objectives 
  1. Conductive hearing loss can be treated with hearing aids, osseointegrated hearing implants, or surgery to restore the tympanic membrane and/or ossicular chain. Explain that each option has inherent advantages and disadvantages. 
  2. Describe the components of a hearing aid and understand how appropriate fitting techniques can lead to improved outcomes.

 

References 
  1. Stach BA, Ramachandran V. “Hearing aid amplification”. In: Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Elsevier/Saunders; 2015:2481-2493
  2. Valente M, Oeding K, Brockmeyer A, Smith S, Kallogjeri D. Differences in Word and Phoneme Recognition in Quiet, Sentence Recognition in Noise, and Subjective Outcomes between Manufacturer First-Fit and Hearing Aids Programmed to NAL-NL2 Using Real-Ear Measures. J Am Acad Audiol. 2018;29(8):706-721

 

Surgical Therapies

Learning Objectives 
  1. Summarize the differences between a medial graft, lateral graft, and the over-under tympanoplasty techniques.
  2. Describe the indications for cartilage tympanoplasties. 
  3. Recognize some differences when performing ossiculoplasty and tympanoplasty using a microscope versus an endoscope.
  4. There are many different osseointegrated implantable devices. Distinguish which patients may benefit from implantable options that bypass the middle ear space.

 

References 
  1. Adams ME, El-Kashlan HK. “Tympanoplasty and ossiculoplasty.” In: Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Elsevier/Saunders; 2015:2177-2188
  2. Dornhoffer J. Cartilage tympanoplasty: indications, techniques, and outcomes in a 1,000-patient series. Laryngoscope. 2003;113(11):1844-1856
  3. Babu S, Luryi AL, Schutt CA. Over-under versus medial tympanoplasty: Comparison of benefit, success, and hearing results. Laryngoscope. 2019;129(5):1206-1210
  4. Isaacson B, Wick CC, Hunter JB. Endoscopic ossiculoplasty. Oper Tech Otolaryngol Head Neck Surg. 2017;28:39-43
  5. Bennett ML, Zhang D, Labadie RF, Noble JH. Comparison of middle ear visualization with endoscopy and microscopy. Otol Neurotol. 2016;37(4):362-366
  6. Vincent R, Sperling NM, Oates J, Jindal M. Surgical findings and long-term hearing results in 3,050 stapedotomies for primary otosclerosis: a prospective study with the otology-neurotology database. Otol Neurotol. 2006;27(8 Suppl 2): S25-47
  7. Cheng HCS, Agrawal SK, Parnes LS. Stapedectomy versus stapedotomy. Otolaryngol Clin North Am. 2018;51(2):375-392
  8. Pross SE, Lustig LR, Della Santina CC. “Implantable hearing devices.” In: Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Elsevier/Saunders; 2015:2411-2427

 

Case Studies

  1. A 42-year-old male with a history of right ear cholesteatoma has undergone five previous right ear surgeries resulting in a canal wall down cavity with a large conductive hearing loss. He gets occasional drainage, especially when the ear is occluded with a traditional hearing aid. Explain the hearing rehabilitation options? What advantages does an osseointegrated hearing implant have in this scenario?
  2. A 25-year-old female with a history of ear tubes as a child presents with a left-sided tympanic membrane perforation and a left conductive hearing loss. She has no problems with her right ear. What are the indications for tympanoplasty? Do all tympanic membrane perforations need to be repaired?
  3. A 47-year-old female reports bilateral conductive hearing loss for the past 15-years. Her right ear is the poorer hearing ear. The hearing loss became noticeable while pregnant. In addition to pure tone averages, word recognition scores, and acoustic immittances are there any other audiometric tests that could be helpful to confirm the diagnosis? Is imaging required for this patient? Which ear would you operate on? How would you counsel on surgical outcomes and complications? 

 

Complications

Learning Objectives 
  1. Cite why tympanoplasties fail and ways to optimize surgical outcomes.
  2. Review expected outcomes and the variability in ossiculoplasty results.
  3. Accurately quote the complication rates associated with stapes surgery, including the risk of complete sensorineural hearing loss.

 

References 
  1. Yung M. Long-term results of ossiculoplasty: reasons for surgical failure. Otol Neurotol. 2006;27(1):20-26
  2. House JW, Teufert KB. Extrusion rates and hearing results in ossicular reconstruction. Otolaryngol Head Neck Surg. 2001;125(3):135-141
  3. Yawn RJ, Hunter JB, O'Connell BP, Wanna GB, Killeen DE, Wick CC, Isaacson B, Rivas A. Audiometric outcomes following endoscopic ossicular chain reconstruction. Otol Neurotol. 2017;38(9):1296-1300
  4. Wiet RJ, Harvey SA, Bauer GP: Complications in stapes surgery. Otolaryngol Clin North Am. 1993;26(3):471-490

 

Review

Review Questions 
  1. What external and middle ear structures derive from the 1st branchial arch, 2nd branchial arch, 1st branchial cleft, and 1st pharyngeal pouch?
  2. Name the different spaces that make up the middle ear.
  3. How does the area ratio and lever ratio contribute to sound conduction?
  4. What is the maximum conductive hearing loss and what clinical scenario would create this type of deficit?
  5. Describe how a third window phenomenon leads to a conductive hearing loss?
  6. Explain the differences between a medial graft tympanoplasty, lateral graft tympanoplasty, and over-under tympanoplasty.

 

Resources 

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  1. Annual Meeting Webcast (AMW):