MechanismThe external ear canal is a tubular structure that conducts sounds and protects the middle ear. Exostosis is a chronic condition characterized by narrowing of the inner half of the ear canal as a result of bone growth. The bony wall grows outward slowly over a period of years in response to local irritation by cold water. These growths are called swimmer's nodes and are common in swimmers, surfers and divers. This condition is not related to infection nor is it caused by infection; however, the narrowing of the ear canal may prevent water from draining out, which increases susceptibility to outer-ear infections. The bony swellings continue to grow while there is a continued exposure to cold water (such as that found in seawater and outdoor swimming pools in temperate climates). Exostosis often occurs in outdoor enthusiasts in their mid- to late-30s, but individuals who experience significant cold-water exposure — such as surfers, swimmers and divers — can develop the condition earlier.
The narrowed ear canal is more prone to blockage by earwax or debris and more susceptible to swimmer's ear (otitis externa). An exostosis on the floor of the ear canal can form a sump that retains moisture and is susceptible to infection. Exostosis is seen as a narrowing of the ear canal. The average ear canal is about 0.25 inches wide (7 milimeters). The bone growth may cause it to narrow to 0.04 inches (1 millimeter). Early signs include water trapping in the ear canal after swimming. Debris trapping and infections may make surgery necessary.
ManifestationsExternal ear infections and difficulty removing water from the external ear canal may be recurrent. Exostosis symptoms in advanced cases include a decreased hearing possibly combined with an increased prevalence of ear infections.
Differential DiagnosisOther causes of external ear-canal obstruction could include infection or earwax (cerumen) impaction.
TreatmentIn case of decreased hearing or repeated infections, exostosis may be removed surgically.
Fitness to DiveExostoses do not affect fitness to dive unless they are occluding the ear canal or causing recurrent infection.
- Wear a hood in cold water.
- After diving, rinse both ears with freshwater to flush contaminated water and salt.
- If prone to ear infections, blow warm air into external canal using a hair dryer (take care to make sure the air is not too hot).
- If your ears have a natural tendency to build up a blockage of earwax, have them checked regularly, particularly before a prolonged diving trip.