Acute mastoiditis sits at the intersection of a common primary care diagnosis and a genuinely life-threatening emergency, making it a recurring theme in FRCEM SBA practice questions and a condition every emergency registrar must manage with confidence. It is the most serious suppurative complication of acute otitis media (AOM), and although its incidence has fallen in the post-antibiotic era, it has not disappeared. Missing coalescent mastoiditis or its intracranial extensions in a febrile child or an adult with ear pain and posterior auricular swelling represents one of the more consequential diagnostic errors in emergency medicine. The RCEM curriculum explicitly includes ENT emergencies and their complications within the knowledge domains assessed at the FRCEM level, and this topic rewards careful revision.
FRCEM SBA practice questions: Key Points: Mastoiditis in the ED
- Acute mastoiditis is the most common serious suppurative complication of AOM and demands urgent ENT referral when clinically suspected.
- The key clinical distinction is between simple AOM with periauricular erythema and true coalescent mastoiditis with posterior auricular fluctuance, pinna displacement, and obliteration of the post-auricular sulcus.
- CT of the temporal bones with contrast is the investigation of choice in suspected coalescent or complicated mastoiditis and should not be delayed when intracranial extension is possible.
- Intravenous co-amoxiclav or ceftriaxone are the typical first-line choices in the ED; cover for MRSA and Pseudomonas must be considered in at-risk groups.
- Intracranial complications including meningitis, cerebral abscess, sigmoid sinus thrombosis, and Bezold abscess require immediate neurosurgical liaison alongside ENT input.
- In FRCEM SBA exam questions, the discriminator is usually the clinical feature that elevates a case from uncomplicated AOM to mastoiditis, or from mastoiditis to complicated mastoiditis requiring imaging or surgical escalation.
Clinical Context and Epidemiology
Acute mastoiditis occurs in approximately 1.2 to 4 per 100,000 children per year in the United Kingdom, with peak incidence in those under 2 years of age. Adults are not immune, and cholesteatoma-related mastoiditis in adults may present insidiously, with a longer prodrome and fewer classic signs. The incidence rose modestly in the late 1990s following shifts in antibiotic prescribing patterns for AOM, though the causal relationship between antibiotic restriction and mastoiditis incidence remains a matter of ongoing debate in the literature. NICE guidance on otitis media recommends a safety-netting approach for uncomplicated AOM rather than routine antibiotics, which places a premium on clinicians recognising features that herald progression to mastoiditis.
Predisposing factors include recent or inadequately treated AOM, cholesteatoma, immunosuppression, tympanic membrane perforation impairing drainage, and anatomical variants such as a narrow aditus ad antrum. In the ED context, the history of recent AOM, ongoing or recurring ear pain, and fever in a child with posterior auricular swelling should prompt immediate clinical assessment for mastoiditis rather than reassurance and discharge.
Pathophysiology: From Otitis Media to Coalescent Mastoiditis
The mastoid air cell system communicates directly with the middle ear cavity via the aditus ad antrum. During AOM, mucosal oedema and inflammatory exudate obstruct this passage, preventing normal drainage from the mastoid air cells. The resulting accumulation of infected material produces an initial stage of inflammatory mastoiditis, sometimes termed mastoiditis with periostitis. At this stage, the bony architecture of the mastoid is intact. Radiologically, clouding of the mastoid air cells is visible on CT, but there is no bony destruction.
If infection is not controlled, proteolytic enzymes released by leucocytes and bacteria begin to erode the thin bony septa between mastoid air cells. This produces coalescent mastoiditis, the true surgical entity, in which the septae are destroyed and a single confluent cavity of infected material forms within the mastoid bone. Periosteal elevation then occurs as the infection tracks laterally, producing the characteristic posterior auricular swelling, fluctuance, and outward displacement of the pinna. At this point, surgical intervention in the form of cortical mastoidectomy is almost invariably required.
Extension beyond the mastoid cortex accounts for the feared complications of this condition. Posterior extension through the mastoid cortex toward the sigmoid sinus produces sigmoid sinus thrombosis, which may present with spiking fevers, Tobey-Ayer sign, and signs of raised intracranial pressure. Superior extension through the tegmen mastoideum reaches the posterior fossa, risking extradural or subdural abscess and meningitis. Medial extension deep to the sternocleidomastoid produces Bezold abscess, presenting as a fluctuant neck mass with torticollis. Anterior extension to the petrous apex produces Gradenigo syndrome, the triad of otorrhoea, ipsilateral abducens nerve palsy, and retro-orbital pain. Each of these complications is a potential FRCEM SBA clinical scenario.
The principal causative organisms are Streptococcus pneumoniae (the most common overall pathogen), Streptococcus pyogenes (Group A Streptococcus, associated with more aggressive and rapidly progressive disease), Staphylococcus aureus including MRSA (particularly in complicated cases), and Pseudomonas aeruginosa (especially in cholesteatoma-related or chronic suppurative disease). Haemophilus influenzae is now less common following widespread Hib vaccination but remains relevant in unimmunised children.
ED Assessment and Management
History and Examination
A focused history should establish the duration of ear symptoms, any prior AOM diagnosis or treatment, antibiotic use, fever trajectory, and the development of new neurological symptoms including headache, vomiting, visual disturbance, diplopia, neck stiffness, or altered consciousness. In adults, enquire about prior ear surgery, chronic otorrhoea, or history of cholesteatoma.
On examination, the posterior auricular region must be inspected carefully. The classic signs of acute mastoiditis are posterior auricular erythema and oedema, obliteration of the post-auricular sulcus, tender fluctuance over the mastoid tip, and anterior and inferior displacement of the pinna. These findings distinguish mastoiditis from simple AOM, where the pinna is not displaced and the post-auricular sulcus is preserved. Otoscopy may reveal a dull, bulging, or perforated tympanic membrane with purulent discharge. A sagging of the posterior superior wall of the external auditory canal is a specific sign of periosteal involvement.
A full neurological examination, including cranial nerve assessment, fundoscopy where feasible, and assessment for meningism, is mandatory. Any cranial nerve deficit, particularly abducens palsy, or signs of meningeal irritation must be treated as evidence of complicated mastoiditis until proved otherwise.
Investigations
Blood tests should include full blood count, CRP, blood cultures (before antibiotics where feasible without delaying treatment), and metabolic profile. Inflammatory markers support the clinical diagnosis and track response to treatment but are neither sensitive nor specific enough to exclude intracranial complications.
Imaging is central to ED management. CT of the temporal bones with intravenous contrast is the investigation of choice for suspected coalescent mastoiditis and should be performed without delay where intracranial extension is clinically possible. CT identifies bony destruction, the extent of mastoid opacification, periosteal collections, and complications including sigmoid sinus thrombosis (characterised by the delta sign on contrast CT), extradural abscess, and subdural collections. MRI with gadolinium provides superior soft tissue resolution and is the preferred modality where intracranial abscess or sinus thrombosis is strongly suspected, though its availability in the acute ED context is more limited. Plain radiographs have no role in the contemporary assessment of suspected mastoiditis.
Antibiotic Therapy
Intravenous antibiotics should be started promptly once cultures have been obtained. In the UK, intravenous co-amoxiclav or ceftriaxone are the standard empirical choices for uncomplicated acute mastoiditis. Ceftriaxone is preferred where meningitis is suspected given its excellent CNS penetration. Where MRSA is a concern (post-surgical patients, complicated or recurrent disease), vancomycin or teicoplanin should be added. Metronidazole is added empirically where anaerobic organisms are suspected, particularly in cholesteatoma-related disease. Clinicians should consult local antimicrobial guidelines and the British National Formulary for current dosing recommendations. Antibiotic choice should be reviewed once microbiological sensitivities are available.
Escalation and Disposition
All patients with confirmed or strongly suspected mastoiditis require urgent ENT referral. Those with evidence of coalescent mastoiditis on CT require surgical planning, typically cortical mastoidectomy. Where intracranial complications are identified, simultaneous neurosurgical liaison is mandatory. Patients with Bezold abscess require surgical drainage. Sigmoid sinus thrombosis may require anticoagulation in addition to surgery; this decision is made jointly with neurosurgery and haematology. No patient with suspected mastoiditis should be discharged from the ED without definitive specialist review.
How the FRCEM SBA Exam Tests Mastoiditis
Mastoiditis features in FRCEM SBA exam questions primarily as a clinical discrimination challenge. The most common question stem presents a febrile child with ear pain and a degree of periauricular inflammation, and asks the candidate to identify the single feature that distinguishes mastoiditis from uncomplicated AOM or periauricular cellulitis. The answer hinges on posterior auricular signs: obliteration of the post-auricular sulcus and anterior displacement of the pinna are pathognomonic of mastoiditis and are the examiners favoured discriminators.
A second category of FRCEM SBA practice questions concerns complications. The clinical stem may describe a child with mastoiditis who develops a sixth nerve palsy (Gradenigo syndrome), a fluctuant neck mass (Bezold abscess), or fever with signs of meningeal irritation. Candidates must identify both the complication and the appropriate escalation pathway. These questions test the application of anatomical knowledge to clinical decision-making, which is precisely the cognitive level the FRCEM SBA is designed to assess.
Antibiotic selection is another area where marks are lost. Candidates who select oral antibiotics for confirmed mastoiditis, or who omit CNS-penetrating cover where meningitis is suspected, will fail these items. The RCEM curriculum domain covering ENT emergencies maps directly to this topic, and the Royal College of Emergency Medicine expects FRCEM candidates to demonstrate senior clinical decision-making in ENT emergencies including their intracranial complications.
High-Yield Revision Pearls
- Anterior and inferior displacement of the pinna with obliteration of the post-auricular sulcus is the key clinical sign distinguishing mastoiditis from simple AOM or periauricular cellulitis.
- Streptococcus pneumoniae is the most common causative organism; Group A Streptococcus is associated with rapid progression and intracranial extension.
- Coalescent mastoiditis involves destruction of the bony septa between mastoid air cells and almost always requires surgical intervention (cortical mastoidectomy).
- Gradenigo syndrome is the triad of otorrhoea, ipsilateral abducens palsy, and retro-orbital pain, indicating petrous apicitis.
- Bezold abscess presents as a fluctuant, tender neck mass with torticollis and indicates medial spread through the mastoid tip into the deep neck spaces.
- CT of the temporal bones with contrast is the first-line imaging modality in the ED; MRI with gadolinium is superior for soft tissue and intracranial complications where available.
- Ceftriaxone IV is preferred empirically where meningitis is a differential diagnosis, given its CNS penetration; co-amoxiclav IV is appropriate for uncomplicated mastoiditis without CNS signs.
- Sigmoid sinus thrombosis produces the delta sign on contrast CT and may require therapeutic anticoagulation in addition to surgical drainage.
Common Pitfalls: Where Candidates Lose Marks
- Attributing post-auricular swelling and erythema to periauricular cellulitis without assessing the post-auricular sulcus and pinna position.
- Failing to perform a cranial nerve examination in a patient with suspected mastoiditis, missing early Gradenigo syndrome or abducens palsy.
- Selecting oral antibiotics for confirmed or strongly suspected mastoiditis in an SBA stem, when intravenous therapy is the correct management.
- Overlooking the need for CT imaging in a patient with mastoiditis and new neurological symptoms, such as headache, diplopia, or neck stiffness.
- Failing to consider cholesteatoma as an underlying aetiology in adults with a history of chronic otorrhoea or prior ear surgery, leading to inadequate antibiotic cover (omitting Pseudomonas cover).
- Conflating the management of complicated mastoiditis with simple AOM, particularly regarding disposition: all patients with mastoiditis require inpatient admission and ENT review.
How EM Learning Centre Supports Your FRCEM Single Best Answer Revision
Mastoiditis exemplifies the type of high-stakes, clinically nuanced topic that the FRCEM SBA exam tests with precision. Questions in this area demand more than factual recall; they require candidates to apply anatomical and pathophysiological reasoning to a clinical scenario under time pressure. Systematic, structured revision across the full breadth of the FRCEM syllabus is the only reliable strategy for consistent performance on exam day.
The FRCEM Single Best Answer revision course at EM Learning Centre is built around exactly this need. The platform provides a comprehensive question bank of FRCEM SBA practice questions covering ENT emergencies, paediatric emergency medicine, critical care, toxicology, trauma, and every other domain on the RCEM curriculum. Each question is accompanied by detailed, consultant-written explanations that teach clinical reasoning rather than simple answer recall, mirroring the cognitive demands of the real exam.
Whether you are beginning your FRCEM SBA exam preparation or fine-tuning your performance in the final weeks before sitting, the EM Learning Centre provides structured, evidence-based resources designed specifically for UK emergency medicine trainees. The platform supports spaced repetition, timed mock exam conditions, and targeted revision by topic, giving you the flexibility to build both breadth and depth across the syllabus. Topics such as mastoiditis, with their interlinking of anatomy, microbiology, clinical decision-making, and emergency escalation, are covered in the depth the Royal College of Paediatrics and Child Health and RCEM curriculum standards demand.
References
- Royal College of Emergency Medicine. RCEM Curriculum and Assessment. Available at: rcem.ac.uk
- National Institute for Health and Care Excellence. Otitis media (acute): antimicrobial prescribing guidance. Available at: nice.org.uk
- British National Formulary. Antibacterials: dosing and prescribing guidance. Available at: bnf.nice.org.uk
- Royal College of Paediatrics and Child Health. Standards and guidance for paediatric emergency medicine. Available at: rcpch.ac.uk
- BMJ Best Practice. Mastoiditis. Available at: bmj.com
- NICE Clinical Knowledge Summaries. Otitis media. Available at: cks.nice.org.uk
