Otitis Media & Otitis Externa
A STEP 2 CK-focused walkthrough of acute otitis media, otitis media with effusion, and acute (including necrotizing) otitis externa — anchored on otoscopic diagnosis, the observe-vs-treat antibiotic algorithm, and the "next best step" for complications like mastoiditis and skull-base osteomyelitis.
The one anatomic split that runs the whole question
Ear-infection questions hinge on a single distinction: is the problem behind the eardrum (middle ear) or in the external canal? In young children the eustachian tube is short, horizontal, and floppy, so a viral URI easily traps fluid in the middle ear; bacterial overgrowth of that effusion is acute otitis media (AOM). When the effusion lingers after the acute infection resolves — fluid without acute inflammation — it is otitis media with effusion (OME), the leading cause of conductive hearing loss and speech delay in kids. Acute otitis externa (AOE), or "swimmer's ear," is a different animal: moisture or trauma disrupts the canal's protective cerumen, letting Pseudomonas aeruginosa (most common) or S. aureus infect the skin of the external auditory canal. Nail the otoscopy and the tragus exam and the rest of the vignette falls into place.
- Diagnosis needs a middle-ear effusion PLUS acute inflammation. Diagnostic pictures: (1) moderate-to-severe bulging of the TM (the most specific sign), (2) new otorrhea not explained by otitis externa, or (3) mild bulging + recent-onset (<48 h) otalgia or intense TM erythema.
- Pneumatic otoscopy is the confirmatory test — a middle-ear effusion shows reduced/absent TM mobility. Tympanometry can corroborate.
- Top 3 pathogens: Streptococcus pneumoniae, nontypeable Haemophilus influenzae, Moraxella catarrhalis.
- Conjunctivitis–otitis syndrome (concurrent purulent pink-eye + ear pain) = nontypeable H. influenzae → treat with amoxicillin-clavulanate.
- Peak age 6–24 months; risk factors: daycare, supine bottle-feeding, tobacco-smoke exposure, pacifier use, and not being breastfed.
- Bullous myringitis (painful bullae on the TM) is usually caused by the same organisms as ordinary AOM (especially S. pneumoniae); the classic "it's Mycoplasma" association is overstated — treat it like AOM.
AOM vs OME vs Otitis Externa
| Feature | Acute Otitis Media (AOM) | Otitis Media w/ Effusion (OME) | Acute Otitis Externa (AOE) |
|---|---|---|---|
| Site | Middle ear (behind TM) | Middle ear (behind TM) | External auditory canal |
| Pain on tragus/pinna tug | No | No | Yes — hallmark |
| Otoscopy | Bulging, erythematous, opaque TM ± otorrhea | Retracted/neutral TM, air-fluid level or bubbles, no acute inflammation | Edematous, erythematous canal with debris; TM normal if seen |
| Pneumatic otoscopy | ↓ mobility (effusion) | ↓ mobility (effusion) | TM mobility normal |
| Top pathogens | S. pneumoniae, NT H. influenzae, M. catarrhalis | Sterile effusion (post-viral / ET dysfunction) | Pseudomonas aeruginosa, S. aureus |
| Fever / systemic | Common in children | Absent | Usually absent |
| First-line Rx | High-dose oral amoxicillin (or observation) | Watchful waiting; tubes if ≥3 mo + hearing loss | Topical fluoroquinolone ± steroid drops |
A 15-month-old, 3 days into a URI, is brought in for fussiness, ear-tugging, and fever to 38.6°C. Otoscopy: bulging, erythematous left TM with an absent light reflex; pneumatic otoscopy shows reduced mobility. The right ear is normal and the tragus is non-tender.
Diagnosis: unilateral, non-severe AOM.
NEXT BEST STEP — observe vs. treat (shared decision): Because this child is 6–23 months with unilateral, non-severe disease and reliable follow-up, either high-dose amoxicillin or 48–72 h observation with a safety-net (delayed) prescription is acceptable.
Treat with antibiotics up front instead if ANY of:
- Severe disease — moderate/severe otalgia, otalgia ≥48 h, or temp ≥39°C
- Otorrhea present
- Bilateral AOM in a child <24 months
- Age <6 months (always treat)
- First-line: high-dose amoxicillin 80–90 mg/kg/day divided BID.
- Use amoxicillin-clavulanate if: amoxicillin within the past 30 days, concurrent purulent conjunctivitis, or recurrent AOM unresponsive to amoxicillin.
- Penicillin allergy (non-severe / non-type-I): a cephalosporin — cefdinir, cefuroxime, or cefpodoxime. Severe / type-I (anaphylaxis): azithromycin or clindamycin (pneumococcal macrolide resistance is common, so both are less reliable).
- Treatment failure at 48–72 h (persistent symptoms): step up to amoxicillin-clavulanate, or IM ceftriaxone × 3 days; consider tympanocentesis for culture.
- Recurrent AOM (≥3 episodes in 6 months or ≥4 in 12 months with ≥1 in the last 6 months) → refer for tympanostomy tubes.
- OME: effusion without acute infection → watchful waiting ~3 months (most self-resolve). Tympanostomy tubes if bilateral effusion + hearing loss persisting ≥3 months; get audiometry for persistent OME with suspected hearing loss.
A 71-year-old with poorly controlled T2DM reports 3 weeks of deep, unrelenting left ear pain, worse at night, plus foul otorrhea unresponsive to antibiotic drops. Exam shows granulation tissue on the floor of the canal at the bony–cartilaginous (osseocartilaginous) junction and a new left facial droop.
Diagnosis: necrotizing (malignant) otitis externa — Pseudomonas aeruginosa skull-base osteomyelitis, not simple swimmer's ear. Pain out of proportion, granulation tissue, and cranial neuropathy (CN VII first) are the giveaways.
NEXT BEST STEP:
- CT of the temporal bone to assess bony erosion (MRI for soft-tissue/intracranial extent).
- Send ESR/CRP (markedly elevated; useful to track) and culture the granulation tissue.
- Start prolonged systemic antipseudomonal therapy (e.g., ciprofloxacin or ceftazidime / cefepime / piperacillin-tazobactam) and get urgent ENT; optimize glucose control.
Do not manage this as routine AOE with drops alone.
A 3-year-old recently treated for AOM returns with fever and a red, tender, boggy swelling behind the ear that pushes the auricle forward and downward; the postauricular crease is effaced.
Diagnosis: acute mastoiditis — the classic suppurative complication of AOM.
NEXT BEST STEP: CT of the temporal bone with contrast (look for coalescent mastoiditis or a subperiosteal abscess) → admit for IV antibiotics → urgent ENT for myringotomy ± mastoidectomy.
Other complications of AOM to recognize: TM perforation, labyrinthitis, facial-nerve palsy, and intracranial spread (meningitis, epidural/brain abscess, sigmoid-sinus thrombosis). Cholesteatoma is a sequela of chronic/recurrent middle-ear disease and TM retraction — not a single acute episode.
- Tragus tug = "outside" (externa): pain when you pull the tragus/pinna localizes to the external canal (AOE). A quiet tragus with a bulging red drum points to AOM.
- AOM's big 3 — "S-H-M": S. pneumoniae, nontypeable H. influenzae, M. catarrhalis (the same trio that causes bacterial sinusitis).
- Conjunctivitis + otitis → "Augmentin": pink-eye-plus-ear = nontypeable H. influenzae → amoxicillin-clavulanate.
- Necrotizing OE = the 3 D's: Diabetic (or otherwise immunocompromised), Deep pain out of proportion (worse at night), Debris = granulation tissue at the osseocartilaginous junction → CT temporal bone + IV anti-*Pseudomonas*.
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