What is the difference between acute mastoiditis and coalescent mastoiditis?

Acute Mastoiditis vs. Coalescent Mastoiditis

Acute mastoiditis refers to inflammation of the mastoid air cells that occurs with every case of acute otitis media, while coalescent mastoiditis is a severe complication characterized by destruction of the bony septa between mastoid air cells, representing a true otolaryngologic emergency that typically requires surgical intervention. 1

Key Pathophysiologic Distinction

Acute (non-coalescent) mastoiditis:

• Fluid accumulation and inflammation within intact mastoid air cells 1
• Bony septa between air cells remain intact 1
• Represents the natural extension of middle ear inflammation into the mastoid 1
• Technically present in all cases of acute otitis media 1

Coalescent mastoiditis:

• Progressive bone destruction with breakdown of bony septa between mastoid air cells 2, 1
• Represents coalescence (merging) of previously separate air cells into larger cavities 3
• Occurs in 84% of clinically significant mastoiditis cases requiring hospitalization 3
• Develops primarily in well-pneumatized temporal bones 4

Clinical Presentation Differences

Both conditions share common features:

• Postauricular swelling and erythema 5, 6
• Mastoid tenderness 5
• Protrusion of the auricle 5, 6
• Fever and ear pain 5
• Bulging, erythematous tympanic membrane 5

Coalescent mastoiditis has additional worrisome features:

• Tympanic membrane perforation with pulsatile purulent discharge 3
• Progressive symptoms despite 48 hours of appropriate IV antibiotics 7, 3
• Subperiosteal abscess formation (occurs in coalescent cases) 7, 3
• Signs of intracranial complications: headache, vertigo, meningismus, neck rigidity, seizures, or neurological deficits 5

Imaging Distinctions on CT Temporal Bone

Acute (non-coalescent) mastoiditis shows:

• Clouding/opacification of mastoid air cells 6
• Intact bony septa between air cells 1
• No bone erosion 1

Coalescent mastoiditis demonstrates:

• Destruction of bony septa between mastoid air cells 2, 1
• Areas of coalescence (merged air cells) 2
• Bone erosion of mastoid structures 2, 8
• Possible tegmen erosion, lateral wall destruction, or other bony complications 9, 5

Management Algorithm

For acute (non-coalescent) mastoiditis:

• IV broad-spectrum antibiotics (high-dose amoxicillin-clavulanate or alternative) 7
• Myringotomy with or without tympanostomy tube placement 7
• Close monitoring for 48 hours 7, 9
• Conservative management is typically successful 3, 6

For coalescent mastoiditis:

• Immediate IV broad-spectrum antibiotics 7
• Myringotomy for drainage and cultures 7
• Surgical intervention (mastoidectomy) is required in all cases of coalescent mastoiditis 3
• Surgery is mandatory if no improvement after 48 hours of IV antibiotics 7, 3
• Surgery is mandatory for subperiosteal abscess 7, 3
• Surgery is mandatory for intracranial complications 7

Critical Clinical Pitfalls

Do not delay imaging when:

• Mastoid tenderness, retroauricular swelling, or auricle protrusion are present 9, 5
• Patient fails to improve after 48 hours of appropriate antibiotics 7, 9
• Any signs of intracranial complications develop 5

Remember that:

• 33-81% of mastoiditis cases occur despite prior antibiotic treatment for acute otitis media 7, 9
• Cultures may be negative in 33-53% of cases, so empiric broad-spectrum coverage is essential 7, 9
• The presence of bony septal destruction on CT is the definitive radiologic criterion distinguishing coalescent from non-coalescent disease 1
• All patients with coalescent mastoiditis require mastoidectomy; conservative management alone is inadequate 3

When intracranial complications are suspected:

• MRI with contrast is superior to CT for detecting meningitis, brain abscess, cerebritis, or dural venous sinus thrombosis 2, 5
• CT venography may be needed to evaluate for sigmoid sinus thrombosis 2