Suppurative infection of the mastoid air cells, usually a complication of acute otitis media — protruding auricle, postauricular swelling, fever.
Also known as: mastoiditis, acute mastoiditis, coalescent mastoiditis
Overview
Acute bacterial infection of the mastoid air cells of the temporal bone, almost always extending from acute otitis media. When inflammation progresses to bony destruction of the mastoid septa, it is termed acute coalescent mastoiditis.
Epidemiology
Most common in children younger than 2 years. Incidence has fallen dramatically with widespread antibiotic use for otitis media but persists, particularly in untreated or partially treated AOM. Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus (including MRSA), Haemophilus influenzae, and Pseudomonas (chronic) are the leading pathogens.
Try two board-style Acute Mastoiditis questions
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Question 1EENTMedium
A 22-month-old boy is brought in for 4 days of worsening left ear pain and fever following an episode of acute otitis media treated 10 days ago. He is irritable and feeding poorly. Temperature is 39.1°C (102.4°F). On exam, the left auricle is displaced forward and downward, and there is erythema, tenderness, and fluctuance over the area behind the ear with loss of the postauricular crease. Otoscopy shows a bulging, erythematous left tympanic membrane. Which of the following is the most likely diagnosis?
AExternal ear canal furunculosis
BAcute suppurative parotitis
CAcute apical petrositis
DAcute coalescent mastoiditis
EAcute postauricular adenitis
Reveal answer & full explanation
Correct answer: D — Acute coalescent mastoiditis
AExternal ear canal furunculosis
BAcute suppurative parotitis
CAcute apical petrositis
DAcute coalescent mastoiditis✓
EAcute postauricular adenitis
Why Acute coalescent mastoiditis is correct
Classic picture: a febrile child younger than 2 with recent or incompletely resolved AOM whose pinna is displaced forward and downward by a tender, fluctuant postauricular mass with loss of the postauricular crease.
Pathophysiology is spread of AOM through the aditus ad antrum into the mastoid air cells, with trapped pus and osteolytic destruction of the bony septa; the bulging erythematous tympanic membrane confirms concurrent middle ear disease.
Diagnosis is clinical and confirmed with contrast CT of the temporal bones; management is admission, IV antibiotics, and myringotomy for drainage and culture, with mastoidectomy reserved for a subperiosteal abscess or coalescent disease that fails medical therapy.
Why the others are wrong
Acute postauricular adenitis: a tender, mobile node behind the ear that does not displace the auricle or produce middle ear findings.
External ear canal furunculosis: localized tenderness on tragal pressure with pus in the canal and no mastoid tenderness, auricular protrusion, or middle ear effusion.
Acute suppurative parotitis: swelling anterior and inferior to the ear that pushes the earlobe up and outward rather than displacing the entire pinna forward, and lacks middle ear disease.
Acute apical petrositis — also a complication of AOM that spreads through pneumatized temporal bone air cells, but infection of the petrous apex classically causes deep retro-orbital pain and abducens palsy with otorrhea (Gradenigo syndrome) rather than a fluctuant postauricular collection that effaces the crease and pushes the pinna forward and downward.
Question 2EENTMedium
A 22-month-old girl is brought in for 12 days of worsening right ear pain and fever that began during an episode of acute otitis media treated with amoxicillin. On exam she is febrile to 39.1°C and irritable. The right auricle is pushed forward and downward, and there is erythema, tenderness, and fluctuance over the mastoid process with loss of the postauricular crease. Otoscopy shows a bulging, erythematous tympanic membrane. She has no neck stiffness, neurologic deficits, or altered mental status. Which of the following is the most appropriate next diagnostic test?
ATympanometry with audiometric testing
BCT of the temporal bones with contrast
CTechnetium-99m bone scan of the temporal bones
DPlain radiographs of the mastoid process
EMR venography of the cerebral sinuses
Reveal answer & full explanation
Correct answer: B — CT of the temporal bones with contrast
ATympanometry with audiometric testing
BCT of the temporal bones with contrast✓
CTechnetium-99m bone scan of the temporal bones
DPlain radiographs of the mastoid process
EMR venography of the cerebral sinuses
Why CT of the temporal bones with contrast is correct
Acute mastoiditis is a clinical diagnosis (AOM signs plus postauricular erythema, tenderness, and auricular protrusion), but the fluctuance here raises concern for a subperiosteal abscess that would change management toward surgical drainage.
Contrast-enhanced CT of the temporal bones is the first-line imaging study: in one study it shows opacification of the mastoid air cells, loss of the bony septa (coalescent disease), a subperiosteal abscess, and any intracranial extension.
Why the others are wrong
Tympanometry with audiometric testing - documents middle-ear effusion and hearing loss, but the bulging tympanic membrane already establishes middle-ear disease, and neither test can show coalescent mastoiditis, a subperiosteal abscess, or intracranial extension, the findings that decide whether surgical drainage is needed.
MR venography of the cerebral sinuses - is the study of choice for sigmoid (lateral) sinus thrombosis, but it is indicated only when an intracranial venous complication is suspected, not as the initial test in mastoiditis with a likely subperiosteal abscess.
Plain radiographs of the mastoid process - were historically used to show clouding of the air cells, but they lack the sensitivity and detail to detect coalescent bony destruction, abscess, or intracranial spread and have been supplanted by CT.
Technetium-99m bone scan of the temporal bones - nuclear bone scanning is sensitive for osteitis and is used when skull base osteomyelitis from necrotizing otitis externa is suspected, but it has poor anatomic resolution and cannot show coalescent septal destruction, a subperiosteal abscess, or intracranial extension, the findings that guide drainage.
Additional high-yield points
Lumbar puncture is reserved for suspected meningitis, and imaging should precede it when an intracranial complication is a concern; this child has no neck stiffness, neurologic deficits, or altered mental status.
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Recent or current acute otitis media, especially untreated or inadequately treated
Recurrent otitis media or chronic suppurative otitis media
Cholesteatoma
Immunocompromise, diabetes mellitus
Age younger than 2 years
Pathophysiology
AOM leads to mucosal inflammation and obstruction of the aditus ad antrum, the narrow channel connecting the middle ear to the mastoid antrum. Trapped pus accumulates within the air cells and, if unresolved, causes osteolytic destruction of the bony septa (coalescent mastoiditis). Pus can then track to the postauricular subperiosteal space (subperiosteal abscess), through the digastric ridge (Bezold abscess in the neck), or intracranially (epidural abscess, sigmoid sinus thrombosis, meningitis, brain abscess).
Clinical presentation
Symptoms
Persistent or worsening otalgia and fever during or after a recent episode of AOM
Postauricular swelling, redness, and pain
Otorrhea if the tympanic membrane has ruptured
Irritability, poor feeding, decreased hearing in young children
Headache or vomiting raise concern for intracranial extension
Signs / physical exam
Protrusion of the auricle forward and downward; loss of the postauricular crease
Erythema, fluctuance, and tenderness over the mastoid process
Bulging, erythematous, or perforated tympanic membrane on otoscopy
Febrile child with a recent AOM whose pinna is pushed out and forward by a tender postauricular mass.
Differential diagnosis
Severe AOM without mastoiditis — Otalgia and middle ear effusion without postauricular swelling, auricular protrusion, or CT mastoid air-cell opacification with bony destruction
Postauricular lymphadenitis — Tender mobile node behind the ear without auricular displacement or middle ear findings
Furuncle of the ear canal — Localized tenderness on tragal pressure; pus from canal; no mastoid tenderness or effusion
Cholesteatoma with chronic mastoiditis — Chronic foul otorrhea, retraction pocket or attic perforation, often Pseudomonas; CT shows soft tissue and ossicular erosion
Postauricular cellulitis from skin source — Skin erythema without protrusion of pinna or middle ear disease
Parotitis — Swelling anterior and inferior to the ear, displaces the lobule outward and upward, but does not push the entire pinna forward
Diagnostic workup
Diagnostic criteria
Diagnosis is clinical: signs of AOM plus postauricular erythema, tenderness, and auricular protrusion, supported by CT showing mastoid opacification with bony destruction in coalescent disease.
Labs
CBC with differential, CRP, blood culture if toxic-appearing
Culture of middle ear or mastoid fluid at the time of myringotomy or surgical drainage to guide antibiotics
Lumbar puncture if meningitis is suspected (after imaging if focal findings or altered mental status)
Imaging
Contrast-enhanced CT of the temporal bones — first-line imaging; demonstrates opacification of mastoid air cells, loss of mastoid septa (coalescent disease), subperiosteal abscess, and intracranial extension
MRI with MR venography if intracranial complication or sigmoid sinus thrombosis is suspected
Tympanocentesis or myringotomy for culture and decompression
Diagnostic algorithm
flowchart TD
A[Acute otitis media<br/>not improving] --> B[Postauricular pain/swelling<br/>+ protruding auricle?]
B -->|Yes| C[CT temporal bone<br/>with contrast]
C --> D{Subperiosteal abscess<br/>or intracranial<br/>complication?}
D -->|No| E[IV antibiotics<br/>+ myringotomy<br/>observe 48 h]
D -->|Yes| F[IV antibiotics<br/>+ mastoidectomy<br/>+ abscess drainage]
E --> G{Improved?}
G -->|No| F
G -->|Yes| H[Transition to PO abx<br/>3-4 weeks total<br/>+ ENT follow-up]
F --> H
B -->|No| I[Treat as severe AOM<br/>reassess in 48-72 h]
Approach to suspected acute mastoiditis.
Treatment
First-line
Hospital admission with intravenous antibiotics
Empiric IV antibiotic — ceftriaxone or ampicillin-sulbactam; add vancomycin if MRSA risk or severe illness; add antipseudomonal coverage (piperacillin-tazobactam, cefepime) for chronic disease
Myringotomy with or without tympanostomy tube for middle ear drainage and culture
Analgesia and antipyretics
Second-line / adjunct
Transition to oral antibiotics (amoxicillin-clavulanate or oral cephalosporin guided by culture) once afebrile and improving, typically completing 3-4 weeks of therapy
Otolaryngology follow-up for hearing assessment and to rule out residual cholesteatoma
Complications
Subperiosteal abscess (most common complication; pus erodes the lateral mastoid cortex); Bezold abscess (pus in upper neck along sternocleidomastoid)
Suspect mastoiditis when AOM is accompanied by postauricular erythema, tenderness, or swelling with a protruding auricle, especially with fever persisting despite antibiotics; it can develop within days of AOM onset.
The pinna in mastoiditis is pushed forward and outward — in parotitis the earlobe is pushed up and out.
CT temporal bone is the imaging study of choice; do not delay surgery if subperiosteal abscess is present.
Always evaluate for intracranial complications when fever, headache, or neurologic findings persist.
Pseudomonas is common in chronic mastoiditis and after long courses of topical or oral antibiotics.
References
Cassano 2020 — Cassano P, Ciprandi G, Passali D. Acute mastoiditis in children. Acta Biomed 2020;91(1-S):54-59
AAP — American Academy of Pediatrics clinical practice guideline: The diagnosis and management of acute otitis media (Lieberthal et al., Pediatrics 2013)
IDSA 2004 — Tunkel AR, Hartman BJ, Kaplan SL, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis 2004;39(9):1267-1284
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