🩺 Introduction
Acute mastoiditis is a suppurative infection of the mastoid air cells, usually a complication of acute otitis media (AOM). Radiology helps confirm diagnosis, assess extent, and detect life-threatening complications (extracranial and intracranial).
⚡ Pathophysiology
- Starts with acute otitis media → infection spreads to mastoid air cells.
- Mucosal edema + pus leads to opacification and coalescence of mastoid air cells.
- Can extend to adjacent bone, soft tissues, venous sinuses, and brain.
🖼️ Imaging Modalities
1. CT Temporal Bone (modality of choice)
- Best for bony anatomy and complications.
- Findings:
- Opacification of mastoid air cells.
- Loss of bony septae (“coalescent mastoiditis”).
- Erosion of mastoid cortex.
- Subperiosteal abscess → collection with periosteal elevation.
- Middle ear opacification (associated).
2. MRI
- Indicated when intracranial complications suspected.
- Findings:
- Soft tissue abscess / subdural empyema.
- Meningitis or cerebritis.
- Sigmoid sinus thrombosis (loss of flow void, filling defect on MRV).
- Enhancement of inflamed mucosa.
🧩 Complications of Acute Mastoiditis
- Extracranial:
- Subperiosteal abscess.
- Bezold abscess (abscess tracking into SCM along digastric groove).
- Zygomatic abscess (into zygomatic root).
- Intracranial:
- Lateral/sigmoid sinus thrombosis.
- Epidural abscess.
- Subdural empyema.
- Brain abscess.
- Meningitis.
📝 Teaching Points
- CT temporal bone → first-line imaging.
- Coalescent mastoiditis = key sign (loss of bony septae).
- Always look for subperiosteal abscess and sigmoid sinus involvement.
- MRI is reserved for suspected intracranial spread.
✅ Conclusion
Acute mastoiditis is not just “opacified mastoid air cells” — radiologists must actively search for bone erosion and complications. CT is the primary modality, while MRI is essential if intracranial spread is suspected. Prompt recognition helps guide antibiotic and surgical management.
