Brain Abscess

Question 1

Definition

Answer 1

focal, intracerebral infection that begins as a localised area of cerebritis and evolves into a collection of pus surrounded by a well-vascularised capsule

Question 2

Types of pathological colonisation

Answer 2

• Haematogenous spread: pathogens enter via bloodstream and are transported to the brain. Can occur in septicemia, bacterial endocarditis, pneumonia, or an abscess elsewhere in the body.
• Direct spread from contiguous foci: infection in nearby structures spreads to brain. e.g. sinusitis, otitis media and dental abscess. Infection can traverse through the bone or spread along the veins that drain these regions
• Direct inoculation : When protective barriers of the brain breached, allowing pathogens to enter directly. E.g. head trauma, neurosurgery, or in rare cases, a penetrating head injury.

Question 3

Aetiology

Answer 3

Streptococci sp:
- V. common esp Strep millers + intermedius
- Assosciated with sinusitis, otitis media and dental infection
Staph aureus:
- Assosciated with haematogenous spread
- Assosciated with direct inoculation
Bacteroides sp:
- Assosciated with sinusitis, otitis media and dental infections

Question 4

Newborn-specific organisms

Answer 4

• Group B Streptococcus
• E.coli
• Listeria monocytogenes

Question 5

Immunocompromised-specific organisms

Answer 5

• Aspergillus
• Candida
• Toxoplasmosis gondii

Question 6

Risk factors

Answer 6

Immunocompromised state
Cyanotic CHD: due to left to right shunt
Local infections: sinusitis, dental infections, meningitis, mastoiditis
Open skull occurrences: neurosurgery, head trauma

Question 7

Signs

Answer 7

• Fever
• Muscle weakness
• Hemiplegia
• Focal neurological deficits:
  = 3rd and 6th cranial nerve palsies
  Signs of meningism: nuchal rigidity

Question 8

Symptoms

Answer 8

Headaches:
- severe
- local to one area of head and refractory to analgesia
Altered mental state: confusion or irritability
Slurred speech
Seizure
Nausea and vomiting

Question 9

Diagnosis

Answer 9

FBC/CRP: raised in infection
CT/MRI: Visualise location, size, and number of abscesses. Typically shows a RING-ENHANCING LESION
Blood cultures: can help identify causative organisms, particularly in haem spread.
Consider:
- Lumbar puncture: avoided due to risk of brain herniation, but performed if meningitis sus
- CT-guided abscess aspiration: in some cases direct aspiration may be performed to identify causative orgnanism

Question 10

Treatment

Answer 10

FIRST LINE:
- Emperical Abx: IV ceftriaxone and metronidazole started until culture results available
= Cef for common
= Met for anaerobes from dental or sinus infection
- Treat underlying cause: any source of infection should be identified and treated properly e.g. anti-fungals = AMPHOTERICIN B
SECOND LINE: Abscess drainage or excision
- for abscesses >2.5cm

Question 11

Complications

Answer 11

• Increased intracranial pressure: if unresolved can lead to herniation and death
• Epilepsy: either 2’ to abscess or post-resection
• Permanent neurological deficits
• Meningitis
• Recurrence of abscess