Key distinguishing features of the most common diagnoses
|Boil||OM||Infective OE||Chronic OM||Reactive OE|
|Other Skin Disease||Possible||No||No||No||Yes|
Small Print:Skull/mastoid X-rays, CT or MRI scan, audiometry.
- Swab of ear discharge: Helps guide treatment in refractory cases.
- Urine for glucose: To exclude underlying diabetes if infections are recurrent (especially boils).
- X-ray of the mastoid process will show a cloudy appearance in the mastoid air cells in mastoiditis.
- CT or MRI scan is the best way to investigate possible invasion of temporal bone by tumour, cholesteatoma.
- Audiometry may be required to assess baseline hearing loss in chronic OM, so improvement after definitive surgical treatment can be measured.
- Skull X-ray: May show middle cranial fossa fracture in CSF otorrhoea (performed in hospital after significant trauma).
- Otitis externa is often recurrent: To minimise future problems, advise the patient to avoid getting water in the ear and stop using cotton buds. Also treat any underlying skin disease.
- In the presence of ear discharge, pain on moving the tragus suggests otitis externa or a boil; in the case of the former, the patient tends to present with itching rather than pain.
- Most cases of otitis externa and media settle with empirical treatment and so don’t require a swab. Only investigate if they do not respond to first-line treatment.
- If the diagnosis is not certain, be sure to follow up after initial treatment to visualise the drum; if persistent discharge makes this impossible, refer to the ENT outpatients department for aural toilet and further assessment.
- Heat, tenderness and swelling over the mastoid process suggests mastoiditis: Refer urgently.
- If ear discharge does not clear with usual therapy, refer for microsuction of debris (aural toilet) to speed resolution and exclude significant middle-ear disease.
- Very rarely, middle-ear infection causing discharge can progress centrally, causing, for example, meningitis or cerebral abscess – so refer immediately any patient with ear discharge who becomes confused or develops neurological signs.
- The use of aminoglycoside or polymyxin drops in the presence of a perforated tympanic membrane carries a risk of ototoxicity (though some specialists do use such drops even if perforation is present). When using potentially ototoxic drops, be as certain as you can about what you are treating.
- Beware severe otitis externa in elderly diabetics or the immunocompromised – it may be the necrotising (‘malignant’) form.