What are the typical presentation, diagnostic workup, and management—including antimicrobial therapy and surgical indications—of mastoiditis in adults?

Mastoiditis in Adults: Presentation, Workup, and Treatment

Clinical Presentation

Mastoiditis is defined by the triad of mastoid tenderness, retroauricular swelling, and protrusion of the auricle—not by imaging findings alone 1. These physical exam findings distinguish mastoiditis from uncomplicated acute otitis media 1.

Key Clinical Features to Assess:

• Retroauricular signs: Swelling, erythema, and tenderness over the mastoid bone are present in all cases of true mastoiditis 2, 3.
• Auricle displacement: The pinna is pushed forward and outward by underlying inflammation 1, 3.
• Otoscopic findings: Bulging and erythematous tympanic membrane, similar to acute otitis media, with possible otorrhea if the membrane has ruptured 1, 2.
• Systemic symptoms: Fever, malaise, otalgia, and hearing loss are common but not universal 2, 3, 4.
• Atypical presentations: Adults frequently present with insidious, latent forms that lack classic findings, making diagnosis challenging 3.

Red Flags for Complications:

• Neurological signs: Headache, altered consciousness, seizures, focal deficits, meningismus, or neck rigidity suggest intracranial extension 1, 5.
• Facial nerve involvement: Facial weakness or paralysis occurs in up to 18% of adult cases 3.
• Vestibular symptoms: Vertigo or hearing loss may indicate labyrinthitis 1, 3.

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Diagnostic Workup

Physical Examination Algorithm:

• Step 1: Perform otoscopy to identify tympanic membrane abnormalities (bulging, erythema, perforation with otorrhea) 1.
• Step 2: Palpate the mastoid region for tenderness and assess for retroauricular swelling 1, 2.
• Step 3: Examine for auricle protrusion and displacement 1, 3.
• Step 4: Conduct a neurological exam to screen for complications (cranial nerve function, meningeal signs) 1, 5.

Imaging Strategy:

CT temporal bone with IV contrast is the definitive imaging study when mastoiditis is clinically suspected 1, 5. This modality provides optimal visualization of bony erosion, coalescence of mastoid air cells, and soft tissue complications 1.

When to Image:

• Immediate imaging: Obtain CT if the diagnosis is uncertain, if complications are suspected, or if the patient fails to improve after 48 hours of IV antibiotics 5, 4.
• MRI with contrast: Reserve for suspected intracranial complications (brain abscess, meningitis, subdural empyema, dural venous sinus thrombosis), as MRI has superior sensitivity for soft tissue and intracranial pathology 1, 5.

Imaging Findings That Mandate Surgery:

• Subperiosteal abscess: Requires IV antibiotics plus mastoidectomy 6, 5.
• Bony erosion: Destruction of the tegmen or lateral mastoid wall indicates advanced disease necessitating surgery 6.
• Coalescence of air cells: Suggests progression beyond simple opacification 1, 5.

Laboratory Studies:

• Blood cultures and inflammatory markers (CBC, CRP, ESR) assess systemic inflammation but should not exclude the diagnosis if normal 4.
• Culture from myringotomy or mastoidectomy: Guides antibiotic therapy, though cultures are negative in 33–53% of cases 1, 7.

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Treatment

Initial Management:

All adults with clinical mastoiditis require immediate IV broad-spectrum antibiotics, with consideration of myringotomy ± tympanostomy tube insertion 5, 4.

Empiric IV Antibiotic Regimens:

• First-line: Ampicillin-sulbactam or ceftriaxone to cover Streptococcus pneumoniae (38.7% of cases) and other common pathogens 5, 4.
• Complicated mastoiditis (with intracranial extension or subperiosteal abscess): Vancomycin plus piperacillin-tazobactam, a carbapenem, or ceftriaxone plus metronidazole to cover resistant organisms and anaerobes 5.
• Confirmed Streptococcus pyogenes: Add clindamycin to penicillin therapy 5.

Pain Management:

• Acetaminophen or NSAIDs for mild-to-moderate pain; consider opioid combinations (oxycodone with acetaminophen or ibuprofen) for severe pain 8.
• Frequent reassessment using pain scales is essential, as mastoiditis pain can be intense due to periosteal involvement 8.

Surgical Indications:

Mastoidectomy is indicated for:

• Subperiosteal abscess identified on imaging 6, 5.
• Bony erosion of the mastoid cortex or tegmen 6.
• Failure to improve after 48 hours of IV antibiotics 5, 3.
• Clinical deterioration at any point during medical management 5.

Surgical Outcomes:

• Conservative management (antibiotics ± myringotomy) achieves cure in 69% of uncomplicated cases and 24% of cases with intracranial complications 3.
• Mastoidectomy is required in approximately 22% of all mastoiditis cases 5.

Transition to Oral Antibiotics:

Once clinical improvement is documented, transition to high-dose oral amoxicillin-clavulanate (2000 mg twice daily) 5.

Alternative Oral Regimens:

• Non-immediate β-lactam allergy: Cefdinir, cefpodoxime, or cefuroxime 5.
• Immediate Type I hypersensitivity: Clindamycin plus cefixime or cefdinir (avoid macrolides due to 20–25% failure rates from pneumococcal resistance) 5.

Monitoring After Transition:

• Reassess within 48–72 hours to ensure continued improvement 5.
• Persistent middle ear effusion is expected in 60–70% of patients at 2 weeks and does not require continued antibiotics unless symptomatic 5.

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Common Pitfalls

• Relying on imaging alone: Incidental mastoid opacification without clinical signs does not constitute mastoiditis requiring treatment 6.
• Underestimating atypical presentations: Adults often lack classic retroauricular findings, leading to delayed diagnosis and higher complication rates (15% meningitis rate in one series) 3.
• Assuming prior antibiotics exclude mastoiditis: 33–81% of mastoiditis cases had received antibiotics before diagnosis 6, 5.
• Delaying imaging in non-responders: Failure to obtain CT after 48 hours of IV antibiotics can miss complications such as intracranial abscess or venous sinus thrombosis 5, 4.
• Using macrolides for step-down therapy: Azithromycin and clarithromycin have unacceptably high failure rates and should be avoided 5.