Synopsis
Recognise focal intracranial suppuration, obtain urgent contrast imaging and blood cultures, coordinate neurosurgical aspiration for microbiology and pressure control, and deliver source-directed prolonged antimicrobial treatment.
- Brain abscess presents with headache, focal neurology, seizure, cognitive change or raised pressure; fever and the full triad are often absent.
- Do not perform lumbar puncture because a focal mass and pressure gradient can precipitate herniation and CSF rarely identifies the organism.
- Use contrast MRI as the most sensitive imaging test; CT is appropriate immediately when MRI is unavailable or the patient is unstable.
- Take blood cultures and identify dental, sinus, ear, lung, cardiac, trauma, surgical and haematogenous sources.
- A stable patient should undergo stereotactic aspiration before antibiotics when this can occur promptly, preserving bacterial, fungal, mycobacterial and molecular specimens.
- An unstable patient receives ceftriaxone 2 g intravenously every 12 hours plus metronidazole 500 mg every 8 hours immediately, modified by source and local protocol.
- Add MRSA-active treatment after neurosurgery, penetrating trauma or defined resistant staphylococcal risk under microbiology guidance.
- Treatment generally continues for weeks and fails when a collection, contiguous source, infected device or endocarditis remains uncontrolled.
Key red flags
Falling consciousness, abnormal pupils or Cushing physiology indicates impending herniation and requires emergency neurosurgical management.
A new focal deficit or seizure with fever or a contiguous ear, sinus or dental source requires urgent contrast brain imaging.
Ventricular rupture, multiloculation or posterior-fossa location carries high mortality and changes operative urgency.
Immune suppression broadens the differential to toxoplasma, fungal and mycobacterial disease and changes specimen handling.
Progressive headache, focal weakness, dysphasia, field loss, personality change or seizure suggests a focal cerebral lesion requiring urgent imaging.
Vomiting, papilloedema, reduced consciousness, sixth-nerve palsy or abnormal pupils indicates mass effect and makes lumbar puncture unsafe.
Recent sinusitis, otitis, mastoiditis or dental sepsis with adjacent frontal or temporal lesion supports direct spread.
Multiple lesions at grey-white junction with bacteraemia, murmur, lung abscess or cyanotic heart disease suggests bloodstream seeding.
Investigation priorities
Define abscess number, location, diffusion restriction, oedema and ventricular involvement.
Management branches
A focal neurological infection or intracranial mass is suspected.
- Use ABCDE, neurological observations and seizure treatment and obtain urgent contrast imaging without lumbar puncture.
- Take blood cultures and involve neurosurgery and infection specialists immediately; start empirical therapy before aspiration when unstable.
- Use corticosteroid only for life-threatening mass effect under neurosurgical advice because it can reduce capsule and diagnostic yield.
- Assess immune state and contiguous, cardiac, pulmonary, traumatic and postoperative sources to guide initial coverage and specimens.