Join us for a discussion about conductive hearing loss (CHL) in adults, a topic that will be relevant to a variety of rotations!

Show Notes

Intro:

Hey everyone and welcome to The Oto Approach, a podcast created by medical students for medical students, to teach you about all things otolaryngology. I'm your host Aileen, and today we're going to talk about Adult Conductive Hearing Loss. Tag along for a discussion about this common presentation within otolaryngology and primary care settings.

According to the Global Burden of Disease Study, which measured years lived with disability, hearing loss is the fourth leading cause of disability globally.1 In 2013, the Canadian Health Measures Survey demonstrated through a study of audiometric results, that 4.6 million Canadians between 20 and 79 or 19% of this population had hearing loss that affected their ability to hear normal speech.2 An even larger subset of the adult population has some degree of hearing loss in the high frequency range, where age-related loss begins.2 The prevalence of hearing loss increases with age, evident as four-frequency hearing loss, affects 65% of people between 70-79, while affecting only 10% of those under 50.2

Hearing loss is a public health issue and disproportionally affects those from lower socioeconomic situations and lower levels of education. The likelihood of having four-frequency hearing loss was 28% among households with an annual income of $50,000, compared to 12% in households with an annual income of $100,000 or more.2 Adults in households with lower education levels were twice as likely to have hearing loss compared to those in households where one or more members was a postsecondary graduate.2

Hearing loss has far-reaching implication, including impaired communication which can negatively impact patients’ relationships and work.Untreated hearing loss can impact the health, psychosocial and economic well-being of individuals, and is associated with higher rates of social isolation, lower quality of life, depression, falls, cognitive decline, dementia and mortality.3,4

Anatomy:

Now that we discussed the prevalence and impact of adult hearing loss, we are going to dive into the basic anatomy of the ear, as pathology contributing to hearing loss may affect one or more components of the anatomy. 

The anatomy of the ear is uniquely constructed to allow for hearing. The ear is divided into three segments: the outer, middle and inner ear. The outer, comprised of the auricle or pinna and external auditory canal, is the part with the most contact with the external world.5 The outer ear or auricle features including the helix, antihelix, tragus and antitragus effectively “catch” sound waves and funnel them down to the external auditory canal.6 The middle ear is an air-filled space, which is divided into the epitympanic recess and tympanic chamber, and contains the ossicles.5 The tympanic membrane separates the outer ear and the middle ear. Sound waves vibrate the tympanic membrane. The ossicles, including the malleus, the incus and the stapes, are bony structures suspended by ligaments which allow them to move and transmit vibrations to the inner ear.5 The inner ear contains the vestibular system, responsible for balance and equilibrium, and the cochlea, which is essential for hearing.7 The piston-like motion of the stapes is effective in transmitting energy to the cochlea through the oval window, resulting in movement of the fluid of the inner ear.6 The cochlea is composed of 3 main fluid compartments, the scala tympani and scala vestibuli containing perilymphatic fluid, and the scala media, containing endolymphatic fluid.7 The Organ of Corti contains inner and outer hair cells, which allow for the transduction of electrical auditory signals.8 The stiffness and size of the hair cells vary throughout the cochlea, which allows the cells to respond to a range of frequencies.8 These are distributed throughout the cochlea such that cells that respond to low frequencies are located near the apex of the cochlea, whereas the cells that respond to high frequencies are at the base of the cochlea. The vibration of the sound waves through the fluid bends the stereocilia on these hair cells. This mechanical energy is then converted to electrical energy which is transmitted to the central nervous system via the cochlear or auditory nerve, a branch of the cranial nerve VIII (8), or the vestibulocochlear nerve.8 The other branch, the vestibular nerve innervates the organs of balance in the inner ear, the semicircular canals and otolith organs and conveys sensory impulses regarding the head and body motion to the brain.9

Classification of Hearing Loss:

Hearing loss may be classified into three types; Sensorineural, Conductive and Mixed. Sensorineural hearing loss involves the inner ear, the cochlea, or the auditory nerve. Conductive hearing loss involves any cause that limits the amount of external sound from gaining access to the inner ear, typically outer or middle ear pathologies. Mixed hearing loss is a combination of sensorineural and conductive loss.6 

Today, we will mainly be focusing on conductive hearing loss, and we will cover sensorineural hearing loss in another episode!  

Outer Ear Causes: 

First, we will review the causes associated with the outer ear which cause conductive hearing loss and the treatments associated with the different causes. 

One of the most common cases of conductive hearing loss is wax or (sa roo min) cerumen impaction. Q-tips or cotton tip applicators are known for worsening impaction.10 There are several methods of removing and softening the cerumen. Warm water irrigation can remove the cerumen in patients without a history of otitis media, perforation of tympanic membrane or otologic surgery.10 An otoscope and curette can also be used to remove the cerumen. Oil or mineral oil can aid in removal by softening the cerumen.10

Foreign bodies in the external auditory canal can also cause unilateral conductive hearing loss. Removal is similar to cerumen typically with a curette.10

Otitis externa is an infection, most commonly caused by Pseudomonas aeruginosa and Staphylococcus aureus, affecting the external auditory canal which can cause conductive hearing loss as swelling and infectious debris can occlude the canal. Treatment of otitis externa involves debridement of the external auditory canal and use of ototopical drops. In severe infections a wick can be placed in the ear and the medication can be delivered over two to three days. The wick helps to stent open the canal so that drops can be delivered effectively.10

Tumors may be another cause of occlusion of the external ear canal. The most commonly malignant tumor is squamous cell carcinoma.6 Treatment is often surgical with adjuvant radiation. Exostosis and osteomas are the two most common benign bony growths that may result in conductive hearing loss by occluding the external auditory canal completely or causing repeat infections as cerumen, skin, infectious debris are prevented from exiting the canal. Patients with exostosis have multiple bilateral growths near the tympanic membrane and often report a history of cold-water swimming.10 Osteomas differ from exostosis as they are single, unilateral and closer to the meatus, at the bony-cartilaginous junction.10 If symptomatic, these growths may be removed surgically. 

Trauma to the external ear canal can also be a cause of conductive hearing. Ototopical drops can be used to prevent otitis externa and EAC stenting can be used to prevent significant stenosis.6

Middle Ear Causes:

Now we will discuss some of the Middle Ear causes which can lead to conductive hearing loss.

Conductive hearing loss can be caused by otitis media, an  infection involving Fluid filling the middle ear space, preventing the tympanic membrane from vibrating, and disrupting the transmission of sound. Otitis media with effusion refers to a condition where the fluid in the middle ear continues to accumulate despite the infection resolving. Otitis media with effusion in adults has been associated with nasopharyngeal carcinoma, and requires investigations as such.11 Lingering fluid in the middle ear usually resolves within 4-6 weeks in 70% of cases.6 In the cases where the fluid does not clear, the fluid can be removed by myringotomy and pressure equalization tube placement or myringotomy and aspiration.6 The symptoms - pressure, decreased hearing and tinnitus, are not well tolerated in adults as compared to children, and thus adults seek this treatment much sooner than is recommended for children. 

The eustachian tube connects the back of the nose (nasopharynx) to the middle ear and functions to protect the middle ear from pathogens, ventilate the middle ear, maintain equal air pressure on either side of the eardrum, and aid in drainage of secretions.12 Dysfunction of this structure, including swelling of the mucosal lining of the tube, or impaired opening and closing, can cause muffled or reduced hearing, or tinnitus.12 This usually occurs in the setting of a viral upper respiratory infection, sinusitis or allergies.6 There are surgical and non-surgical treatment options for eustachian tube dysfunction, depending on the etiology, but there is limited consensus about such management.12 

Cholesteatomas are another cause of conductive hearing loss, and occur as a result of squamous epithelium in the middle ear.13 Cholesteatomas can be locally destructive, causing erosion of the ossicular chain, mastoid, and external auditory canal. However - cholesteatomas, despite their name, are not a cancer. Poor eustachian tube function or tympanic membrane trauma can increase the risk of cholesteatomas. Treatment is surgical, typically involving a tympano mastoidectomy.6

Otosclerosis is the leading cause of hearing loss in adults without a history of middle ear effusion or otitis media.12 It is notably more prevalent in women, is often a familial disorder, and typically presents in early adulthood with gradual onset.13 This is caused by fixation of the stapes footplate to the oval window, which impairs the motion of the stapes. Treatment can include hearing aids or surgery. The surgery, a stapedectomy, involves removing the fixed part of the stapes bone with a laser or micro-drill and replacing it with a mobile prosthetic bone.14 

Tympanic membrane perforation is another common cause of conductive hearing loss, by impairing the vibrational pattern of the tympanic membrane. This perforation can be caused by various factors such as trauma or infection, or iatrogenic causes such as myringotomy and tube insertion.15 The signs and symptoms of perforation include sudden onset pain, followed by relief and drainage from the ear or otorrhea.15 The size and location of the perforation impacts the degree of hearing loss, larger and posterior/superior located perforations increase risk of significant hearing loss. Perforations tend to heal spontaneously without intervention, but the healing process can also be aided by utilizing a paper or biogenic film patch. Occasionally surgical correction is required to correct the perforation.6 

Middle ear barotrauma can also result in tympanic membrane perforation and conductive hearing loss. Barotrauma refers to injury or trauma due to exposure to changes in pressure, which are often sudden or large during diving, flying, or hyperbaric oxygen treatment. The eustachian tube aids in maintaining equal pressure on either side of the tympanic membrane, equilibrating to the ambient pressure, allowing us to experience changes in pressure without damage to the ears. However, if this equalization is impeded on by mucosal edema secondary to an upper respiratory tract infection, pregnancy or anatomic variations, the negative pressure in the middle ear can cause serous fluid of blood accumulation or inward rupture of the tympanic membrane.6 Treatment includes topical and systemic decongestants, analgesics and antihistamines.6 

History

Now we are going to review some of the important aspects of a history in the context of adult hearing loss. Any patient presenting with hearing loss should have a full auditory history and examination. It is critical to ask about onset and progression and if they are experiencing unilateral or bilateral loss. Through the history you can also gain an understanding of how the hearing loss affects the patient, asking about how well they can understand spoken words, if the problem is mainly with noise backgrounds or if it is equally present in quiet settings as well. Additionally, you can ask about associated tinnitus, vertigo or disequilibrium, or if they have experienced headache or visual disturbances around the time of the episodes of hearing loss. It is also important to ask about pain or drainage from the ear. It is essential to inquire about some of the causes that we reviewed such as trauma, major infection, previous ear surgery and other medical conditions, such as diabetes, coronary artery disease and autoimmune diseases. Social history is also important in this clinical context and asking about their job and the nature of noise level at the workplace. Excessive noise exposure can affect the degree of (prez buh cue sis) presbycusis, or age related hearing loss, that develops, and exposure to loud noises can cause high-frequency sensorineural hearing loss, but again, we will get more into sensorineural hearing loss in a future episode- so stay tuned for that!6 Family history of hearing loss is also important information to gather. Finally, inquiring about medications, both prescribed and over the counter. 

Physical and Investigations:

There are some aspects of the physical examination and testing that can occur in a primary care office setting, however many patients also require formal audiological testing or other specialized tests. There are also a variety of free smartphone apps that can perform screening audiograms, including “uHear” which has been validated in a number of peer reviewed studies against the gold standard pure tone audiometry.16 This technology is particularly helpful in situations where formal audiograms are not accessible. 

In the office setting, methods to evaluate hearing include whispered voice test, tone-emitting otoscope, questionnaires and tuning forks. The whispered voice test is often introduced to medical students in clinical skills and involves standing at arm’s length behind the patient, as they cover one ear, and whispering a sequence of words such as “ninety-nine,” then asking them to repeat what they heard.24 This is repeated for the opposite ear. Screening for hearing loss with a tone-emitting otoscope has been shown to be the most effective screening method, compared to questionnaires. 

Tuning forks can be utilized to perform Weber and Rinne tests, which can help distinguish the location and type of hearing loss the patient is experiencing. The Weber test is conducted by placing the vibrating tuning fork on the midline of the forehead, or bridge of the nose, then asking the patient where the loudest sound is experienced, on the right, left or middle. The vibrations will be conducted through the bone to the cochlea, and in normal hearing or symmetrical hearing loss the sound is heard in the middle, equal on both sides.25  The Weber test suggests sensorineural hearing loss if the sound is louder on the patient’s reported “good” side, and conductive hearing loss is considered if the sound is louder on the bad side.24 Rinne test differentiates sound transmitted through air conduction from bone conduction via the mastoid bone.26 The tuning fork handle is placed on the mastoid bone behind the ear and the patient is asked to report when the sound is no longer audible, then the fork is brought away from the bone near the ear canal and asked if they can hear the sound now. Another way to complete this test is asking the patient if the tuning fork is louder on the bone or by the ear. A normal test result would be hearing the sound again once the fork is brought in close proximity to the ear or hearing it louder when by the ear, demonstrating air conduction is better than bone conduction.24 The Weber and Rinne test work together to help differentiate conductive and sensorineural hearing loss. An abnormal Rinne test suggests conductive loss, particularly if the Weber test also lateralizes to that side. In the case the Rinne test is normal in an ear where the Weber test showed lateralization to that same ear, the Rinne test must be conducted on the opposite ear. If this test is normal in this ear, it is suggestive of sensorineural hearing loss.24

The auricle and external auditory canal should also be examined. An otoscope can be utilized to visualize the tympanic membrane and recognize any middle ear abnormalities, such as perforations in the tympanic membrane. Pneumatic otoscopy can be used to assess the mobility of the tympanic membrane. When air is forced into the auditory canal, the tympanic membrane should move down and when the pressure is released the tympanic membrane should be pulled outward.17 Formal audiologic assessment should be performed for patients who do not have a known cause for the hearing loss. 

When an etiology for hearing loss is not clear, referral to an otolaryngologist is recommended. 

Clinical Pearls

Here are some clinical pearls from our resident team, including good FYIs and frequently quizzed topics on ENT rotations:

Interpreting audiograms is a key skill for otolaryngologists and can be especially beneficial for clerks when reviewing hearing tests. Here are some pearls related to audiogram interpretation for conductive hearing loss:

• A notched decrease in hearing decibels at ~2000 Hz is called Carhart’s notch and can be a classic sign of otosclerosis.

• A notched decrease in hearing decibels at ~4000 Hz is often associated with noise-induced hearing loss.

• Adults with age-related hearing loss otherwise known as presbycusis will have decreasing hearing decibels in the higher frequencies.

• Patients with conductive hearing loss will classically have a “air-bone gap” where hearing tested through the air is reduced compared to hearing through the bone. As bone related hearing relies solely on sensorineural hearing loss and air related hearing relies on sensorineural as well as conductive hearing loss.

We would like to extend our sincerest thanks to the Saint John Regional Hospital Department of Surgery within the Horizon Health Network for their generous support. 

Thank you so much for listening to our podcast! We hope you’ll tune in to our next episode! Please head to our website at www.theotoapproach.com for our show notes, and to sign up for our newsletter to stay up to date with our latest episodes.

References:

1. GBD 2015 Disease and Injury Incidence and Prevalence Collaborators. Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet Lond Engl. 2016;388(10053):1545-1602. doi:10.1016/S0140-6736(16)31678-6

2. Government of Canada SC. Prevalence of hearing loss among Canadians aged 20 to 79: Audiometric results from the 2012/2013 Canadian Health Measures Survey. Published July 15, 2015. Accessed September 28, 2021. https://www150.statcan.gc.ca/n1/pub/82-003-x/2015007/article/14206-eng.htm

3. Cunningham LL, Tucci DL. Hearing Loss in Adults. N Engl J Med. 2017;377(25):2465-2473. doi:10.1056/NEJMra1616601

4. Government of Canada SC. Unperceived hearing loss among Canadians aged 40 to 79. Published August 21, 2019. Accessed September 28, 2021. https://www150.statcan.gc.ca/n1/pub/82-003-x/2019008/article/00002-eng.htm

5. Sánchez López de Nava A, Lasrado S. Physiology, Ear. In: StatPearls. StatPearls Publishing; 2021. Accessed September 29, 2021. http://www.ncbi.nlm.nih.gov/books/NBK540992/

6. Weber P. Etiology of hearing loss in adults. UpToDate. Published September 2021. Accessed September 29, 2021. https://www.uptodate.com/contents/etiology-of-hearing-loss-in-adults?search=ear%20anatomy&source=search_result&selectedTitle=7~150&usage_type=default&display_rank=7#H2

7. Impairments NRC (US) C on DD for I with H, Dobie RA, Hemel SV. Basics of Sound, the Ear, and Hearing. National Academies Press (US); 2004. Accessed September 29, 2021. https://www.ncbi.nlm.nih.gov/books/NBK207834/

8. White HJ, Helwany M, Peterson DC. Anatomy, Head and Neck, Ear Organ of Corti. In: StatPearls. StatPearls Publishing; 2021. Accessed September 29, 2021. http://www.ncbi.nlm.nih.gov/books/NBK538335/

9. Landau ME, Barner KC. Vestibulocochlear nerve. Semin Neurol. 2009;29(1):66-73. doi:10.1055/s-0028-1124024

10. Isaacson J, Vora NM. Differential Diagnosis and Treatment of Hearing Loss. Am Fam Physician. 2003;68(6):1125-1132.

11. Mills R, Hathorn I. Aetiology and pathology of otitis media with effusion in adult life. J Laryngol Otol. 2016;130(5):418-424. doi:10.1017/S0022215116000943

12. Llewellyn A, Norman G, Harden M, et al. Interventions for adult Eustachian tube dysfunction: a systematic review. Health Technol Assess Winch Engl. 2014;18(46):1-180, v-vi. doi:10.3310/hta18460

13. Sooriyamoorthy T, De Jesus O. Conductive Hearing Loss. In: StatPearls. StatPearls Publishing; 2021. Accessed October 5, 2021. http://www.ncbi.nlm.nih.gov/books/NBK563267/

14. Stanford Medicine. Otosclerosis and Stapes Surgery. Stanford Medicine. Otolaryngology⁠ — Head & Neck Surgery (OHNS). Accessed October 11, 2021. https://med.stanford.edu/ohns/OHNS-healthcare/earinstitute/conditions-and-services/conditions/otosclerosis.html

15. Park H, Hong SN, Kim HS, et al. Determinants of Conductive Hearing Loss in Tympanic Membrane Perforation. Clin Exp Otorhinolaryngol. 2015;8(2):92-96. doi:10.3342/ceo.2015.8.2.92

16. Bright T, Pallawela D. Validated Smartphone-Based Apps for Ear and Hearing Assessments: A Review. JMIR Rehabil Assist Technol. 2016;3(2):e13. doi:10.2196/rehab.6074

17. Weber P. Evaluation of hearing loss in adults. UpToDate. Published August 2021. Accessed September 25, 2021. https://www.uptodate.com/contents/evaluation-of-hearing-loss-in-adults?search=adult%20hearing%20loss&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2#H1

18. Wahid NWB, Hogan CJ, Attia M. Weber Test. In: StatPearls. StatPearls Publishing; 2021. Accessed October 13, 2021. http://www.ncbi.nlm.nih.gov/books/NBK526135/

19. Kong EL, Fowler JB. Rinne Test. In: StatPearls. StatPearls Publishing; 2021. Accessed October 1, 2021. http://www.ncbi.nlm.nih.gov/books/NBK431071/

20. National Institue on Deafness and other Communication Disorders. Age-Related Hearing Loss (Presbycusis) — Causes and Treatment. NIDCD. Accessed October 11, 2021. https://www.nidcd.nih.gov/health/age-related-hearing-loss

21. Wright T. Menière’s disease. BMJ Clin Evid. 2015;2015:0505.

22. Halliday J, Rutherford SA, McCabe MG, Evans DG. An update on the diagnosis and treatment of vestibular schwannoma. Expert Rev Neurother. 2018;18(1):29-39. doi:10.1080/14737175.2018.1399795

23. Ciorba A, Corazzi V, Bianchini C, et al. Autoimmune inner ear disease (AIED): A diagnostic challenge. Int J Immunopathol Pharmacol. 2018;32:2058738418808680. doi:10.1177/2058738418808680

24. Kuhn M, Heman-Ackah SE, Shaikh JA, Roehm PC. Sudden Sensorineural Hearing Loss. Trends Amplif. 2011;15(3):91-105. doi:10.1177/1084713811408349

25. Rauch SD. Idiopathic Sudden Sensorineural Hearing Loss. N Engl J Med. 2008;359(8):833-840. doi:10.1056/NEJMcp0802129

26. Weber P. Sudden sensorineural hearing loss in adults: Evaluation and management. UpToDate. Published July 14, 2021. Accessed September 25, 2021. https://www.uptodate.com/contents/sudden-sensorineural-hearing-loss-in-adults-evaluation-and-management?search=otosclerosis&topicRef=6844&source=see_link#H1