Notes · ENT · 27 October 2026

Acute mastoiditis

Definition

• Acute mastoiditis is a bacterial infection of the mastoid air cells that develops rapidly, usually as a complication of acute otitis media (AOM).
• It is characterised by inflammation, pus formation, and possible bone erosion within the mastoid process of the temporal bone.

Epidemiology

• Incidence has fallen in the post‑antibiotic era to about 1–2 cases per 100 000 children per year, but it remains the most common serious complication of AOM.
• Peak age: 6 months to 5 years; rare in adults unless there is chronic ear disease or immunosuppression.
• Slight male predominance (≈55 % male).
• Higher rates reported in low‑resource settings where early antibiotic treatment for AOM is less accessible.

Aetiology

• Primary organisms (culture from middle ear or mastoid pus):
  • Streptococcus pneumoniae (≈30 %)
  • Staphylococcus aureus (including MRSA) (≈20 %)
  • Haemophilus influenzae (non‑typeable) (≈15 %)
  • Streptococcus pyogenes (≈10 %)
• Anaerobes (e.g., Fusobacterium, Prevotella) are more common in chronic or delayed presentations.
• Recent rise in Pseudomonas aeruginosa infections in children with tympanostomy tubes.
• Risk factors: delayed or inadequate treatment of AOM, immunodeficiency, craniofacial anomalies, prior ear surgery, and exposure to tobacco smoke.

Pathophysiology

1. Spread of infection – The middle ear cavity is connected to the mastoid air cell system via the aditus ad antrum. Bacterial invasion of the middle ear can extend through this narrow channel.
2. Air‑cell inflammation – Inflammatory exudate fills the air cells, increasing intramastoid pressure.
3. Bone erosion – Persistent pressure and enzymatic activity (e.g., collagenases) cause osteitis and cortical bone loss, creating a pathway for pus to dissect into adjacent soft tissues.
4. Compartmental spread – The mastoid is adjacent to the sigmoid sinus, facial nerve canal, and posterior cranial fossa; infection can extend to these structures, producing serious complications.

Clinical Features

• Ear pain (otalgia) that worsens despite standard AOM therapy.
• Post‑auricular swelling – tender, erythematous, often fluctuant; may develop a “post‑auricular abscess” (also called a “mastoiditis bump”).
• Protrusion of the auricle – due to underlying edema (“pinna displacement”).
• Fever – usually >38 °C, may be high‑grade.
• Otoscopic findings – bulging tympanic membrane, possible perforation with purulent discharge (otorrhoea).
• Systemic signs – irritability in infants, malaise, leukocytosis.
• Red flag symptoms – neck stiffness, vomiting, seizures, or focal neurological deficits suggest intracranial spread.

Investigations

Management (Guidelines 2024)

Initial Medical Therapy

• Empiric intravenous (IV) antibiotics started promptly after cultures are taken:
  • First‑line: Ceftriaxone 50 mg/kg IV every 12 h (max 2 g) plus clindamycin 10 mg/kg IV every 8 h (covers MRSA and anaerobes).
  • Alternative (penicillin‑allergic): Vancomycin 15 mg/kg IV every 6 h plus cefepime 50 mg/kg IV every 8 h.
• Duration: Minimum 10–14 days IV, followed by oral antibiotics (e.g., amoxicillin‑clavulanate 45 mg/kg/day divided 3×) to complete a total of 4–6 weeks if there is bone involvement or intracranial complication.

Surgical Intervention

• Indications:
  • Presence of a subperiosteal abscess >2 cm, fluctuance, or skin breakdown.
  • Failure of clinical improvement after 48–72 h of appropriate IV antibiotics.
  • Evidence of intracranial extension, facial nerve palsy, or venous sinus thrombosis.
• Procedures:
  • Mastoidectomy (can be cortical or modified radical depending on disease extent).
  • Abscess drainage – incision and drainage of post‑auricular collection, often combined with mastoidectomy.
  • Myringotomy with tympanostomy tube – to ventilate the middle ear and obtain pus for culture.

Supportive Care

• Antipyretics (paracetamol 15 mg/kg/dose q6h).
• Adequate hydration (≥30 mL/kg/day).
• Analgesia with NSAIDs if no contraindication.

Follow‑up

• Clinical review at 48 h to assess fever, pain, and swelling.
• Repeat imaging (CT or MRI) only if deterioration or new neurological signs.
• Audiological assessment 4–6 weeks after completion of therapy to detect residual conductive loss.

Complications

High‑Yield Exam Points

• Triad of acute mastoiditis: post‑auricular pain/swelling, fever, and otorrhoea or perforated tympanic membrane.
• Most common organism: Streptococcus pneumoniae (but always cover MRSA and anaerobes empirically).
• Imaging of choice: High‑resolution CT of the temporal bone – shows air‑cell opacification and bony erosion.
• First‑line IV antibiotics (2024): Ceftriaxone + clindamycin (covers typical and atypical pathogens).
• Surgical threshold: Subperiosteal abscess >2 cm, or lack of improvement after 48 h of IV antibiotics.
• Complication to never miss: Sigmoid sinus thrombosis – look for persistent headache, papilledema, and consider MRI/MRV.
• Audiology: Conductive hearing loss is common; always arrange post‑treatment audiogram.
• Differential diagnosis: Cellulitis of the post‑auricular region, cholesteatoma, otitis externa, and temporal bone fracture.

Practice questions

1. A 3‑year‑old child presents with fever, otorrhoea, and a tender, fluctuant swelling behind the ear. HRCT shows opacified mastoid air cells with cortical erosion. Which of the following is the most appropriate initial antibiotic regimen (according to 2024 guidelines)?
A. Amoxicillin‑clavulanate oral only
B. Ceftriaxone IV plus clindamycin IV
C. Azithromycin oral single dose
D. Vancomycin IV alone

Answer: B — ceftriaxone plus clindamycin provides broad coverage for typical organisms, MRSA, and anaerobes.

2. Which complication of acute mastoiditis is best diagnosed with magnetic resonance venography (MRV)?
A. Subperiosteal abscess
B. Facial nerve palsy
C. Sigmoid sinus thrombosis
D. Conductive hearing loss

Answer: C — MRV visualises venous sinus thrombosis.

3. In a child with acute mastoiditis who fails to improve after 72 hours of appropriate IV antibiotics, the next step is:
A. Increase the dose of the same antibiotics
B. Switch to oral antibiotics
C. Perform mastoidectomy with abscess drainage
D. Observe for another 48 hours

Answer: C — surgical drainage is indicated when there is no clinical response within 48–72 hours.

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AI-assisted study material for exam revision. Always confirm with standard textbooks and current guidelines; not medical advice.