This article is on external auditory exostosis (EAE). This resource is open to everyone. Patients, Medical Students and General Practitioners may find this useful. Adjacent boxes provide additional information for Medical Practitioners.
What is External auditory exostosis (EAE)
External auditory exostosis (EAE) is a benign irreversible bone growth projecting into the ear canal in response to repeated exposure to cold water or cold air for over a long period of time (Kroon et al., 2002).
How does the EAE occur?
Ear canal is a bony passage protected by a thin layer of skin. Entrance of cold water or cold air irritates the ear canal and stimulates new bone formations protruding into its lumen. This results in progressive narrowing of the ear canal (Kroon et al., 2002). When the narrowing is significant enough, the obstruction can occur and causes symptoms which will be discussed below.
What is a purposed mechanisms of EAE formation?
Repeated exposure of external auditory canal to cold water or cold air stimulates the formation of new bone at the tympanic ring. The exact mechanisms of EAE development is still unknown. It was suggested that exposure to cold air or cold water stimulates osteoblasts of the temporal bone causing bone to grow into the ear canal. This, perhaps, occur in order to protect the tympanic membrane from the low temperature (Harrison, 1962).
Who gets EAE?
EAE occurs most commonly in people who are repeatedly exposed to cold water or cold air. It is most classically associated with surfing, therefore, it is also known as “surfers ear” (Kroon et al., 2002). Other groups of people that are at higher risk of developing EAE are swimmers, divers, kayakers, and sailors (Kroon et al., 2002; Landefeld et al., 2020). A study reports that the risk of EAE development increases by 12% per one extra year of cold water exposure (Reddy et al., 2011). Severity of the disease increases with colder temperature and longer duration of exposure to cold water or cold air (Kroon et al., 2002; Reddy et al., 2011).
EAE is common in New Zealand because of our long coastline. It is also common in the West Coast of the U.S. and the Coast of Australia (Hurst et al., 2004)
In general populations, the prevalence of EAE is 3-6% (DiBartolomeo, 1979; Mlynski et al., 2008). In at risk population with frequent contact with cold water, the prevalence range between 38.0% to 89.96%. (Kroon et al., 2002; Lambert et al., 2021)
What are the symptoms?
Usually patients with EAE are symptom-free (Reddy et al., 2011; Wegener et al., 2021). Symptoms occur as the disease progresses, specifically when the bone growths have become so large that they cause obstruction (Kroon et al., 2002).
Patients may initially find it difficult to clear water from their ears. They may have fullness or blocked sensation within their ears following water activities and find that they must shake their head vigorously or hop to clear water from their ears (Reddy et al., 2011). When there is water or debris trapping within the ear canal, the patients are at increased risk of developing otitis externa (ear canal infection, also known as “swimmer’s ear”) (Landefeld et al., 2020). Therefore, patient with EAE may present with recurrent ear infections (Landefeld et al., 2020). When there is infection, patients may experience ear pain, ear itching, and ear discharge with or without hearing loss and jaw pain (Hajioff & MacKeith, 2015). Ear infection in patients with EAE may take longer time to heal as the infection debris cannot be effectively cleared due to the increased swelling from inflammation of the already narrowed ear canal (DiBartolomeo, 1979).
EAE patients may develop chronic cerumen impaction (building up of earwax leading to blockage of ear canal) when the narrowing is large enough to impact the normal self-cleansing process of the ear canal. This may result in conductive hearing loss (Turetsky et al., 1990).
Rarely patients may have hearing impairment due to severe narrowing or complete blockage of the ear canal by the bony growth (Turetsky et al., 1990).
How is it diagnosed?
EAE is diagnosed by using otoscope to visualize bony outgrowths protruding into the ear canal.
How to grade EAE severity?
There are four grades of EAE severity based on level of ear canal obstruction caused by EAE as seen on otoscopy (Nakanishi et al., 2011).
Grade 0 – normal ear canal, no visible exostosis
Grade 1 – obstruction of up to 33%
Grade 2 – obstruction of 34–66%
Grade 3 – obstruction of 67–100%.
Can you prevent Exostoses?
Stopping cold water or cold air from entering the ear canal is the key for EAE prevention (Reddy et al., 2011). This can be achieved by regular use of physical ear protections such as ear plugs and neoprene wetsuit hood or headband (Alexander et al., 2015; Landefeld et al., 2020). Avoiding water activities during cold weather is also recommended (Alexander et al., 2015).
What are the treatment options?
If EAE is detected at early stages, it often does not require treatment. Disease progression can be slowed down by following the prevention strategies above.
Symptomatic patients can be managed conservatively in the early stages. Removal of obstructive earwax can be done in the clinic setting. For patients with symptoms of water trapping, the use of high concentration alcohol ear drop is shown to effectively dry and acidify the ear canal resulting in reduced risk of infection (Wang et al., 2005).
When to refer patient for ENT specialist assessment?
Referral to ENT service is recommended for grade 3 lesions, patients with recurrent ear infection or progressive hearing loss, or when there are concerns for alternative diagnoses such as tumour. Patient should have an audiogram done before the referral has been made (Simas et al., 2016).
When ear infection develops, it can be managed with pain relief, topical antibiotics with or without steroid (e.g., Sofradex and Ciproxin HC) and oral antibiotics (if the infection become severe and spread to the adjacent tissues).
Surgical removal is the only definitive treatment of EAE. It is recommended when EAE became so large that it causes recurrent water trapping, recurrent infection, or significant hearing loss (Alexander et al., 2015; Reddy et al., 2011). It is normally performed as a day surgery. The patients will be put to sleep (under general anesthesia). It is common to have pain after the surgery. It is important that the patients refrain from water activities for 6-8 weeks post-surgery to allow complete healing.
Surgery to remove EAE can expose the patients to risk of complications such as rupture of eardrum, hearing loss, injury to nearby nerves, infection, delayed healing process and ear canal narrowing (Hurst, 2001). It is also important to note that surgical intervention does not prevent recurrences. Therefore, patient who had surgical treatment still need to follow the preventative measures to avoid further development of EAE (Hurst et al., 2004).
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Author + Affiliation:
Dr Thitapon Uiyapat, Whanganui Hospital
Date of Publication +/- Review: