Is an Infected Burr Hole Considered a CNS Infection?
Yes, an infected burr hole should be considered a central nervous system (CNS) infection and managed accordingly with CNS-penetrating antibiotics and appropriate surgical intervention. This is a neurosurgical device-related infection that directly communicates with the intracranial space and requires treatment similar to other CNS infections.
Clinical Reasoning
An infected burr hole represents a direct portal between the external environment and the CNS. The infection can manifest as:
- Subdural empyema - pus collection in the subdural space 1
- Meningitis/ventriculitis - inflammation of meninges or ventricular system 2, 3
- Brain abscess - focal parenchymal infection 4
- Wound infection with intracranial extension 5
The key distinction is whether the infection is limited to superficial tissues around the burr hole or has extended intracranially. Any intracranial extension constitutes a CNS infection and demands aggressive management.
Diagnostic Approach
Imaging
- MRI with contrast and DWI is superior to CT for distinguishing infection from hematoma recurrence 1
- Look for abnormal signal within the burr hole itself - this may be an early indicator of infection even without other inflammatory findings 5
- Subdural empyema typically appears within 1 month of the initial procedure 1
CSF Analysis
- In febrile patients with intracranial devices, CSF should be obtained for analysis 6
- Send for Gram stain, culture, cell count with differential, glucose, and protein 6
- Blood cultures should also be obtained 4
Common Pitfalls
- Do not rely on CT alone - it cannot reliably distinguish empyema from hematoma recurrence 1
- Consider infection if "recurrence" occurs within 1 month of drainage 1
- Fungal infections can present years after the initial procedure and may be missed without pathological examination 7
Microbiology
The most common pathogens include:
- Staphylococcus aureus (including MRSA) - most common 4
- Coagulase-negative staphylococci 4
- Gram-negative organisms (Klebsiella pneumoniae, E. coli) 2
- Fungi (Candida parapsilosis) - rare but can occur with significant delay 7
Treatment Algorithm
1. Surgical Management
Craniotomy is preferred over repeat burr hole drainage for established subdural empyema 1. The evidence shows:
- Burr hole drainage alone often fails, requiring subsequent craniotomy 1
- Wide craniotomy allows complete evacuation of pus and infected membranes 1, 2
- Remove any infected hardware if present 4, 8
2. Antimicrobial Therapy
For MRSA or suspected staphylococcal infection:
- IV vancomycin for 4-6 weeks 4
- Consider adding rifampin 600 mg daily or 300-450 mg twice daily 4
- Alternative: linezolid 600 mg PO/IV twice daily (better CSF penetration at 66% vs vancomycin's 1-5%) 4
For gram-negative organisms:
- Adjust based on culture and susceptibility
- Ensure adequate CSF penetration of chosen agent
For fungal infections:
- Amphotericin B deoxycholate 1 mg/kg IV daily or liposomal AmB 5 mg/kg daily 8
- Step-down to fluconazole 12 mg/kg daily for susceptible isolates 8
- Continue until all clinical, CSF, and radiological abnormalities resolve 8
3. Duration
- Minimum 4-6 weeks for bacterial infections 4
- Longer if inadequate source control or clinical response
- For fungal infections, continue until complete resolution of all abnormalities 8
Key Considerations
CSF penetration matters: Vancomycin achieves only 1-5% CSF penetration with maximum concentrations of 2-6 μg/mL, which may be marginal 4. Linezolid achieves 66% penetration with CSF concentrations of 7-10 μg/mL 4. This pharmacokinetic advantage makes linezolid a reasonable alternative, particularly for difficult-to-treat infections.
Complications to monitor:
- Ventriculitis (higher risk with intraventricular catheters - 42.8% vs 0% with intraparenchymal) 9
- Recurrence requiring repeat surgery 1
- Systemic complications (pneumonia, bacteremia) 7
Distance from burr hole to wound exit predicts outcomes: EVD distance >11.5 mm from wound exit to burr hole predicts mortality with 88% sensitivity and 83% specificity 3. This emphasizes the importance of proper surgical technique.
The evidence consistently supports treating infected burr holes with intracranial extension as true CNS infections requiring prolonged CNS-penetrating antibiotics and aggressive surgical debridement 4, 1, 2.