Brain abscess

Question 1

Define brain abscess

Answer 1

Suppurative collection of microbes (most often bacterial, fungal, or parasitic) within a gliotic capsule occurring within the brain parenchyma. Lesions may be single or multi-focal.

Question 2

Aetiology of brain abscesses

Answer 2

Bacteria: contiguous spread from a parameningeal site e.g. sinus, middle ear / haematogenous e.g. endocarditis
- Strep. Pyogenes
- Staph. Aureus
- Bacteroides fragilis
- Enterobacter
- Klebsiella
- Neisseria meningitides
Fungal:
- Aspergillus fumigates
- Candida albicans
- Cryptococcus neoformans
Parasitic:
- Toxoplasmosa gondii
- Trypanosoma
- Echinococcus granulosus

Question 3

Risk factors for brain abscesses

Answer 3

Previous infection: sinusitis, otitis media, dental infection, meningitis
Recent head and neck surgery
Recent neurosurgery
Recent dental work
Congenital heart disease
Infective endocarditis
Diabetes mellitus
HIV/immunocompromise
IVDU
Chronic granulomatous disease
Male

Question 4

Symptoms and signs for brain abscesses

Answer 4

Fever (not the swinging pyrexia seen with abscesses)
Headache (raised ICP): dull and persistent

Seizures
Meningism: + Kernig or Budzinski sign
Neuro:
- Localising signs e.g. third/sixth nerve palsy
- Bacterial abscesses = peripheral
- Toxoplasma abscesses = deeper; basal ganglia
Fundoscopy:
Papilloedema

Question 5

Investigations for brain abscesses

Answer 5

FBC: raised WCC
CRP/ESR: raised
Clotting/cross match/group and save
Blood cultures

MRI head contrast: ring enhancing lesion
CT head with contrast: ring enhancing lesion

Question 6

Management for brain abscesses

Answer 6

Urgent neurosurgical referral: decompression

1. Sepsis 6
   
   1. IV Abx: vancomycin 15mg/kg + Metronidazole 500mg IV + ceftriaxone 2g IV
2. Supportive
   
   1. Decompensating → dexamethasone 10mg IV single dose (treatment in infection/sepsis controversial)
   2. Seizures/abscess near motor cortex → levetiracetam
3. Source of infection found
   
   1. Bacterial → continue abx
   2. Fungal → amphotericin B ± flucytosine
   3. Parasitic → pyrimethamine + sulfadiazine
4. Surgical
   Craniotomy to debride the cavity

Question 7

Complications of brain abscesses

Answer 7

Abscess rupture → ventriculitis
SIADH → hyponatraemia
Cognitive dysfunction (esp. in children)
Seizures
Hydrocephalus
Death

Question 8

Prognosis for brain abscesses

Answer 8

Overall mortality <13%
Permanent hemiparesis and long-term seizures under 50%
Early diagnosis and prompt treatment correlates with improved outcome