OME (or chronic serous otitis media) can follow AOM if the ear fails to heal properly, and is also common in young children (again, the theory suggests that Eustachian tube dysfunction is the main underlying risk/cause for OME). It is usually described as the presence of effusion for more than one month (to differentiate from AOM).
Eustachian tube dysfunction (usually blockage secondary to underdevelopment and AOM) causes a negative pressure in the middle ear (due to air being absorbed/diffused into the mucosal cells)- which then draws out transudative, serous discharge from the mucosa.
Note how this process is essential sterile, i.e. no pathogen and no antibiotic treatment is needed. HOWEVER, there may be an underlying perpetuating infection of the nose/throat (occasionally in the ear) that can prevent resolution. It is important to look for signs of URTIs or allergies.
Unlike AOM, pain and discomfort are very rare symptoms. Hearing problems are more common, especially in young children, and the first sign may be watching TV too loud or not doing well at school. A feeling of fullness is also usually present.
If the membrane is perforated, a persistant serous discharge will also be present, but this is not always the case.
At otoscopy, the patient may have a bulging membrane with fluid behind it (loss of landmarks and light reflex). They don’t have any signs of infection e.g. redness, injection etc. as with AOM.
Tympanometry (tests the movement of the membrane in response to pressures) will usually show type B results (i.e. no movement) since the pressure behind the drum prevents any further movement.
The diagnosis, however, is often clinical.
If symptoms persist for over 3 months and are having significant impact on hearing/development etc, then surgery is usually the first option. A Grommet’s insertion procedure involves cutting open the ear drum (myringotomy) and inserting a tube to equalise the pressure).