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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- AOM requires acute symptoms plus middle-ear effusion and inflammation; a bulging tympanic membrane is the highest-yield exam finding
- Most common organisms: Streptococcus pneumoniae, nontypeable Haemophilus influenzae, Moraxella catarrhalis; viral URI often precedes bacterial AOM
- First-line treatment when antibiotics are indicated: high-dose amoxicillin 80-90 mg/kg/day divided BID
- Use amoxicillin-clavulanate if amoxicillin in the past 30 days, concurrent purulent conjunctivitis, or recurrent AOM unresponsive to amoxicillin
- Observation for 48-72 h is reasonable in selected nonsevere cases; analgesia is required for all patients
Overview
Acute otitis media is an acute infection of the middle ear space caused by eustachian tube dysfunction after viral upper respiratory infection. Negative middle-ear pressure and impaired drainage allow bacterial overgrowth and purulent effusion. Diagnosis should not be made on ear pain alone: Step 2 CK expects objective otoscopy, especially moderate-to-severe tympanic membrane bulging, new otorrhea not caused by otitis externa, or mild bulging with recent-onset ear pain or intense erythema. Otitis media with effusion is fluid without acute infection and should not be treated with antibiotics.
Epidemiology
AOM is one of the most common pediatric infections and antibiotic indications in the United States, peaking between 6 and 24 months of age. Risk factors include day-care attendance, smoke exposure, lack of breastfeeding, craniofacial abnormalities, pacifier use, allergic rhinitis, and recent viral URI. Pneumococcal and influenza vaccination reduce some episodes but do not eliminate AOM. Adults can develop AOM, but persistent unilateral effusion in an adult requires evaluation for nasopharyngeal obstruction or malignancy.
Clinical Features
Symptoms
Otalgia or ear tugging, often after viral URI symptoms
Fever, irritability, poor sleep, or decreased feeding in infants
Transient conductive hearing loss or aural fullness
Otorrhea if tympanic membrane perforates
Severe otalgia for >=48 h or temperature >=39 C suggests severe AOM
Postauricular pain, swelling, or protruding pinna suggests mastoiditis
Signs
Bulging, opaque, erythematous tympanic membrane with reduced mobility on pneumatic otoscopy
Middle-ear effusion: air-fluid level, bubbles, or impaired tympanic membrane mobility
Normal ear canal helps distinguish AOM from otitis externa
Perforated tympanic membrane may show purulent otorrhea
Postauricular erythema, edema, and auricular displacement are red flags for acute mastoiditis
Investigations
First-line
Pneumatic otoscopyBest initial diagnostic examination. Bulging TM and reduced mobility support AOM; a red TM alone is nonspecific and can occur with crying or fever
TympanometryObjective evidence of middle-ear effusion when otoscopy is uncertain; flat type B tracing supports effusion
Hearing assessment if persistent effusionOME lasting >=3 months or suspected language delay warrants age-appropriate audiology
Second-line
Culture of otorrheaIf chronic drainage, tympanostomy-tube otorrhea, immunocompromise, or treatment failure
Re-examination at 48-72 hRequired if observation chosen or symptoms fail to improve on antibiotics
Specialist
ENT referralRecurrent AOM (>=3 episodes in 6 months or >=4 in 12 months with 1 in last 6 months), persistent effusion with hearing difficulty, structural TM abnormalities, or suspected mastoiditis
CT temporal boneNot routine. Use if mastoiditis, intracranial complication, facial nerve palsy, or severe atypical disease suspected
1
Analgesia for all patients
- Acetaminophen or ibuprofen for pain and fever; topical anesthetic drops may be used if tympanic membrane is intact
- Do not rely on antibiotics for immediate pain relief; analgesia is a separate treatment step
2
Antibiotics vs observation
- Immediate antibiotics: age <6 months; age 6-23 months with bilateral AOM; severe symptoms; otorrhea; immunocompromise; craniofacial abnormality; unreliable follow-up
- Observation 48-72 h: selected children >=6 months with nonsevere unilateral AOM and reliable follow-up; also selected older children with mild bilateral disease
- Adults with clear bacterial AOM are generally treated rather than observed
3
First-line antibiotic choices
- High-dose amoxicillin 80-90 mg/kg/day divided BID for 5-10 days depending on age and severity
- Amoxicillin-clavulanate if amoxicillin in past 30 days, purulent conjunctivitis (H influenzae), or amoxicillin failure
- Non-anaphylactic penicillin allergy: cefdinir, cefuroxime, cefpodoxime, or ceftriaxone
- Anaphylactic beta-lactam allergy: azithromycin or clindamycin may be used, but coverage is less reliable
4
Treatment failure and recurrent disease
- Failure = persistent severe symptoms or no improvement after 48-72 h; switch amoxicillin to amoxicillin-clavulanate or give ceftriaxone
- Tympanostomy tubes may be offered for recurrent AOM if middle-ear effusion is present at assessment
- Do not use prophylactic antibiotics for recurrent AOM
Complications
- Tympanic membrane perforation: Otorrhea with pain relief; usually heals spontaneously
- Otitis media with effusion: Persistent conductive hearing loss after infection clears
- Mastoiditis: Postauricular swelling, erythema, protruding pinna — requires IV antibiotics and ENT
- Intracranial spread: Meningitis, brain abscess, sigmoid sinus thrombosis; suspect with severe headache, neurologic signs, or toxic appearance
- Facial nerve palsy: Rare complication from temporal bone inflammation
USMLE Step 2 CK Exam Tips
- 1Bulging tympanic membrane is the key diagnostic clue; a red tympanic membrane alone is not enough
- 2AOM + purulent conjunctivitis = nontypeable H influenzae — choose amoxicillin-clavulanate, not amoxicillin alone
- 3Otitis media with effusion has fluid but no acute infection; do NOT give antibiotics
- 4Severe AOM or age <6 months = antibiotics; mild unilateral disease in an older child can be observed
- 5Postauricular swelling + protruding pinna after AOM = mastoiditis — CT temporal bone + IV antibiotics + ENT
- 6Recurrent AOM with effusion at assessment = tympanostomy tube candidate
- 7Pain control is always part of management even when antibiotics are prescribed
practicetest your knowledge on acute otitis mediaApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — ent and beyond.
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