Brain abscesses & other NS infections

Question 1

What are the different types of primary bacterial infections of the CNS?

Answer 1

• Meningitis
• Encephalitis
• Ventriculitis
• Brain abscess
• Subdural empyema
• Eye infections
• Ventriculoperitoneal shunt & external ventricular drain infection

Question 2

Define a brain abscess

Answer 2

A focal suppurative process within the brain parenchyma (pus in substance of the brain)

Question 3

What organism can cause a brain abscess?

Answer 3

• Bacterial cause depends on pathogenic mechanism
• Polymicrobial
• Streptococci 70%
• Staph aureus 15% most common after trauma/surgery
• Anaerobes
• Gram -ve enteric bacteria
• Fungi (mycobacterium TB, toxoplasma gondii)

Question 4

What are the 4 ways in which a brain abscess can develop?

Answer 4

• Direct spread form contiguous suppurative focus (ear, teeth, sinuses)
• Haematogenous spread from distant focus (endocarditis, bronchiectasis)
• Trauma (open cranial fracture, post neuro surgery)
• Cryptogenic

Question 5

What is the clinical presentation of a brain abscess?

Answer 5

• Headache (most common)
• Focal neurological deficit (30-50%)
• Confusion
• Fever
• Nausea/vomiting
• Dizziness/seizures
• Neck stiffness
• Coma (papilloedema)

Question 6

What is the initial management of a brain abscess?

Answer 6

1. Urgently reduce intracranial pressure
2. Confirm diagnosis
3. Obtain pus for micro investigation
4. Enhance efficacy of antibiotics
5. Avoid spread of infection into ventricles

Question 7

How are brain abscesses treated?

Answer 7

• Drainage is treatment of choice
• Antibiotics which penetrate into CSF/ brain tissue
• Ampicillin, penicillin, cefuroxime, cefotaxime, ceftazidime, metronidazole all achieve therapeutic conc in intracranial pus

Question 8

What are immediate complications of a brain abscess?

Answer 8

• Raised intracranial pressure, mass effect, coning

- Rupture (into ventricles) causing ventriculitis

Question 9

Describe subdural empyema

Answer 9

• Infection between dura & arachnoid
• Causes: usually polymicrobial anaerobes, sure, aerobic gram -ve bacilli, strep pneumoniae, ham influenza, staph aureus
• Spread of infection from sinuses, middle ear & mastoid, distant site following surgery/trauma
• Urgent surgical drainage of pus/antimicrobial agents

Question 10

What are common causes of ventriculoperitoneal shunts & external ventricular drain infections?

Answer 10

• Device inserted into ventricles to monitor intraventricular pressure or drain excess CSF
• Colonised with organisms that cause ventriculitis
• Mostly coagulase-negative staph
• Treat my removing device & intraventricular antibiotics