Cerebral Abscess

Background/Epidemiology

• Incidence ~ 0.3-1.3/100,000/year; more common in males; average age is 40 years
  • Prevalence is higher amongst patients with HIV infection (particularly opportunistic protozoal and fungal abscesses)
• Bacteria usually have a source of origin e.g. penetrating injury, direct spread from sinuses or middle ear or secondary to septicaemia (more likely if there are multiple abscesses)
  • The location of the abscess may give a clue as to the origin and type of bacteria
  • 
    • *Metastatic abscesses is a term used to describe those originating from the blood i.e. septicaemia.  This may be secondary to endocarditis, pulmonary infections etc.

Presentation

• Acute fever, headache, meningism and drowsiness.
  • Can also present as more insidiously as raised intracranial pressure without signs of infection
    • e.g. seizures, focal signs and headache

Investigation

• Always perform CT before LP to establish a mass lesion (i.e. if there are any symptoms of raised ICP)
  • Low density lesion(s); ring enhancement with contrast and surrounding oedema
  • In any case an LP is NOT helpful in diagnosing abscess (but may be helpful in diagnosing meningitis).  If an abscess is seen on CT, an LP is generally not required in the first instance.
  • MRI may be more detailed (for surgical aspiration)
• FBC may show elevated WCC and CRP/PV (if infection is active)
  • Blood cultures
• Because abscesses are particularly rare in the UK, if there is no particular underlying source/cause, consider testing for HIV

Management

• For suspected bacterial abscess (not protozoal/fungal)- High dose IV ceftriaxone and metronidazole (+ IV flucloxacillin if Staph aureus a possibility e.g. in trauma-related abscess)
  • This is usually given for a prolonged course IV (several weeks)
    • NB Consult infectious diseases/microbiology; vancomycin may be considered in some cases
• Aspiration is also performed in most cases (surgery)
  • sample of the abscess may be sent for culture/sensitivity and appropriate antibiotics used after surgery
  • burrhole drainage or excision may be necessary in persistent capsulated abscesses
• Follow-up imaging

Prognosis/Complications

• Mortality remains ~10-20%- early diagnosis/management is important
• Epilepsy is a common complication (up to 30%) and is often refractory to treatment

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