In an otherwise healthy adult with sudden painful swelling over the mastoid (posterior ear) and mild otalgia, what is the most likely diagnosis and recommended initial work‑up and management?

Acute Mastoiditis

This presentation of sudden painful bony swelling over the mastoid with ear pain is acute mastoiditis until proven otherwise, and you must obtain CT imaging of the temporal bone with IV contrast immediately to confirm the diagnosis and rule out complications. 1

Key Diagnostic Features

The critical distinguishing features of mastoiditis versus simple otitis media are:

• Mastoid tenderness on palpation 1
• Retroauricular swelling and erythema 1, 2
• Protrusion or displacement of the auricle (pinna pushed forward/outward) 1, 3
• These findings are not present in uncomplicated acute otitis media 1

The bony swelling you describe is pathognomonic for mastoiditis—this represents periosteal inflammation and potential subperiosteal abscess formation. 2, 3

Immediate Workup

Imaging is mandatory and should not be delayed:

• CT temporal bone WITH IV contrast is the definitive first-line study 1
• IV contrast improves detection of inflammatory tissue, abscesses, and complications critical for management decisions 1
• CT will confirm bone destruction, coalescence of mastoid air cells, and identify subperiosteal abscess 1, 4

Laboratory studies to obtain:

• Complete blood count with differential 1
• Inflammatory markers (ESR, CRP) 1
• Blood cultures if systemic infection suspected 1

Critical Red Flags Requiring Urgent Evaluation

Assess immediately for these complications that mandate emergent intervention:

• Headache, vertigo, or meningismus 5, 1
• Neck rigidity or seizures 5, 1
• Cranial nerve deficits or neurological symptoms 5, 1
• Facial nerve weakness 6

If any of these are present, obtain MRI brain with and without IV contrast in addition to CT, as MRI is superior for detecting intracranial complications including meningitis, brain abscess, cerebritis, subdural empyema, or dural venous sinus thrombosis. 5, 1

Initial Management

Begin treatment immediately while awaiting imaging:

• Admit for intravenous antibiotics with antistaphylococcal and antipseudomonal coverage 5
• Common organisms are Streptococcus pneumoniae, Staphylococcus aureus, and Pseudomonas aeruginosa 5
• Pain control is essential: Use acetaminophen or NSAIDs for mild-moderate pain; severe pain may require opioid combinations 1
• Reassess pain frequently using standardized scales, as periosteal inflammation produces intense pain 1

Surgical Decision-Making

The need for surgery depends on CT findings and clinical response:

• Myringotomy ± tympanostomy tube placement can be sufficient in early disease without bony erosion 5, 7
• Mastoidectomy is indicated if:
  • Subperiosteal abscess is present 5, 2
  • Clear signs of bony necrosis or coalescence 5, 2
  • Failure to improve after 48 hours of IV antibiotics 5, 1
  • Clinical deterioration 5, 1

Contemporary evidence supports that some cases with subperiosteal abscess can be managed with needle aspiration plus myringotomy without mastoidectomy, though this remains controversial. 5

Common Pitfalls to Avoid

Do not dismiss this as simple otitis externa or otitis media—mastoid tenderness with bony swelling is a specific warning sign requiring imaging. 1, 6

Do not delay imaging when posterior auricular swelling is present—this indicates potential extension beyond the middle ear and mastoid. 5, 6

Do not be falsely reassured by prior antibiotic treatment—33-81% of mastoiditis cases had received antibiotics for presumed otitis media before developing mastoiditis. 5, 1

Do not rely on normal inflammatory markers to exclude mastoiditis—clinical examination findings take precedence. 6

Obtain intraoperative cultures if surgery is performed—these are the most reliable for microbiological diagnosis, though cultures may be negative in 33-53% of cases. 1, 2