How does secretory otitis media cause painless hearing loss?

Secretory otitis media causes painless hearing loss because the middle-ear cavity becomes filled with noninfected fluid rather than air. This condition occurs when the eustachian tube fails to provide adequate ventilation to the middle ear.1

When the eustachian tube is blocked—often due to a cold, allergies, or enlarged adenoids—the air normally present in the middle ear is gradually absorbed by the mucous membrane. As this air is not replenished, fluid accumulates in its place. This fluid buildup physically impedes the vibratory movements of the tympanic membrane and the ossicular chain, which are essential for transmitting sound. Because the fluid is noninfected and the condition lacks the inflammation associated with acute infection, the resulting impairment of hearing occurs without the pain typically associated with other forms of otitis media.12