What is the most appropriate next step in diagnosis for a 3-year-old boy with persistent ear pain, fever, and signs of possible mastoiditis after completing a 10-day course of amoxicillin (amoxicillin)?

CT Scan is the Most Appropriate Next Diagnostic Step for Suspected Mastoiditis

A CT scan of the head (option B) is the most appropriate next step in diagnosis for this 3-year-old boy with suspected acute mastoiditis.

Clinical Presentation Analysis

The patient presents with several concerning features that strongly suggest mastoiditis:

• Persistent right ear pain despite completing a 10-day course of amoxicillin
• Fever of 38.9°C (102°F)
• Downward and lateral displacement of the right auricle
• Tenderness to palpation of the posterior auricular area

These clinical findings, particularly the displacement of the auricle and posterior auricular tenderness, are pathognomonic for mastoiditis, which is a serious complication of acute otitis media that has failed to respond to initial antibiotic therapy.

Diagnostic Approach

When mastoiditis is suspected based on clinical presentation, imaging is essential to:

1. Confirm the diagnosis
2. Assess the extent of disease
3. Identify potential complications (intracranial or extracranial)

Why CT Scan is the Correct Choice:

• CT scan provides detailed visualization of the mastoid air cells, middle ear, and surrounding structures
• It can identify bony erosion, coalescence, subperiosteal abscess, or intracranial complications
• Recent evidence suggests that the presence of bony erosion significantly impacts management decisions 1

Why Other Options Are Not Appropriate:

• Bone scan (A): Less specific, provides limited anatomical detail, and is not the standard imaging modality for acute mastoiditis
• Tympanometry (C): While useful for diagnosing middle ear effusion 2, it cannot assess mastoid involvement or complications
• Lumbar puncture (D): Would only be indicated if meningitis is suspected, but the patient has a supple neck without signs of meningeal irritation
• Tympanocentesis (E): While helpful for identifying pathogens in treatment-resistant otitis media 2, it does not evaluate the extent of mastoid involvement

Management Considerations

After confirming mastoiditis with CT imaging, treatment typically involves:

1. Hospitalization for intravenous broad-spectrum antibiotics
2. Consideration of surgical intervention if:
   • No clinical improvement after 48 hours of IV antibiotics 3
   • Evidence of complications such as subperiosteal abscess or intracranial extension
   • Bony erosion or coalescence on imaging 1

Recent studies indicate an increasing incidence of mastoiditis with more complicated cases requiring surgical intervention 4. The most common pathogens include Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus 5, 6.

Conclusion

For this 3-year-old boy with clinical signs of mastoiditis after failed antibiotic treatment for otitis media, a CT scan of the head is the most appropriate next diagnostic step to confirm the diagnosis, assess the extent of disease, and guide appropriate management.