How is mastoiditis diagnosed?

Diagnosing Mastoiditis

Mastoiditis is diagnosed through a combination of clinical examination findings and imaging studies, with the key clinical distinction from acute otitis media being the presence of mastoid tenderness, retroauricular swelling, and protrusion of the auricle. 1

Clinical Diagnostic Features

• The primary clinical signs of mastoiditis include:

  • Mastoid tenderness on palpation 1, 2
  • Retroauricular swelling 1, 2
  • Protrusion of the auricle 1, 2
  • Postauricular erythema 2
  • Fever (most common presenting symptom) 3, 2

• Otoscopic findings similar to acute otitis media (AOM) may be present:

  • Bulging tympanic membrane 1
  • Erythema of the tympanic membrane 1
  • Limited or absent tympanic membrane mobility 1
  • Otorrhea (if tympanic membrane has ruptured) 1, 2

• Important to note: Classic physical findings may be absent in many cases, making diagnosis challenging 3

Diagnostic Algorithm

1. Initial Clinical Assessment:

   • Evaluate for ear pain, fever, and otoscopic findings of AOM 1
   • Specifically examine for mastoid tenderness, swelling, or auricle protrusion 1
   • Consider mastoiditis in patients with otitis media or fever of unknown origin 3

2. Laboratory Testing:

   • Laboratory analysis may reveal evidence of systemic inflammation 2
   • Note that normal white blood cell count and inflammatory markers should not be used to exclude the diagnosis 2

3. Imaging Studies:

   • CT temporal bone with contrast is the preferred initial imaging modality for suspected mastoiditis 1, 4, 2
   • Imaging is indicated when:
     • Diagnosis is uncertain 2
     • Subperiosteal abscess is suspected 5
     • Patient fails to improve after 48 hours of adequate medical therapy 4, 5
     • Focal neurological signs are present 5
     • Complications are suspected 4

4. Additional Imaging:

   • MRI with contrast is superior for detecting intracranial complications such as meningitis, cerebritis, subdural empyema, or brain abscess 4, 6

Common Pitfalls and Caveats

• Mastoiditis is often overlooked because it is uncommon and may not present with a clearly diagnostic set of physical findings 3

• Mastoiditis can develop despite prior antibiotic treatment for AOM (33-81% of mastoiditis cases had received antibiotics previously) 1

• Relying solely on otoscopic findings may miss mastoiditis; always examine the mastoid area in cases of severe or persistent AOM 1

• Plain radiographic evidence of mastoiditis is usually not apparent early in the disease course 3

• Signs suggesting complications that require immediate attention include:

  • Headache, vertigo, meningismus, neck rigidity, seizures, or neurological deficits 1
  • These may indicate serious complications like subperiosteal abscess, labyrinthitis, meningitis, intracranial abscess, subdural empyema, or dural venous sinus thrombosis 1

• CT and MRI imaging should be reserved for children with suspected mastoiditis-related intracranial complications rather than used routinely 5