What is the best treatment approach for a patient with a history of ventriculoperitoneal (VP) shunt placement, presenting with symptoms of ventriculitis, Enterococcus faecalis infection, and moyamoya-like changes, mimicking primary angiitis of the central nervous system (PACNS)?

Treatment of VP Shunt-Associated Enterococcus faecalis Ventriculitis with Moyamoya-like Changes

The optimal treatment approach requires complete removal of the infected VP shunt, placement of an external ventricular drain (EVD), intravenous ampicillin therapy (or alternative agents for resistant strains), and delayed shunt reimplantation only after achieving CSF sterility. 1

Immediate Surgical Management

Complete shunt hardware removal is essential for successful treatment of bacterial VP shunt infections. 2, 1 The evidence strongly supports this approach:

• Remove all components of the infected shunt system immediately rather than attempting in situ treatment, as success rates are significantly lower when the shunt remains in place 2, 1
• Place an external ventricular drain (EVD) to manage hydrocephalus during the treatment period 2, 1
• Shunt externalization (partial removal) is an alternative option, though complete removal is generally preferred for bacterial infections 2
• Delayed shunt replacement after CSF sterilization is the standard approach for bacterial shunt infections 2, 1
• Single-stage replacement (immediate reimplantation) may only be considered for organisms of low pathogenicity, which does not apply to Enterococcus faecalis 2

Antimicrobial Therapy for Enterococcus faecalis

First-Line Treatment

For ampicillin-susceptible Enterococcus faecalis, intravenous ampicillin is the drug of choice:

• Ampicillin 200 mg/kg/day IV in 4-6 divided doses for 6 weeks (8 weeks for prosthetic valve endocarditis, which may guide duration for prosthetic device infections) 2
• Addition of gentamicin 3 mg/kg/day IV or IM in 1 dose for 2-6 weeks enhances bactericidal activity, though some experts recommend only 2 weeks of aminoglycoside therapy 2
• Monitor renal function and gentamicin levels weekly (twice weekly in renal impairment) 2
• Treatment duration for CNS infections should be 21 days minimum after achieving CSF sterility 1

Alternative Regimens for Resistant Strains

For ampicillin-resistant E. faecalis (as in your case report):

• Vancomycin 30 mg/kg/day IV in 2 doses plus gentamicin 3 mg/kg/day for 6 weeks is an alternative regimen 2
• Maintain vancomycin trough levels ≥20 mg/L; AUC/MIC >400 is recommended 2
• Daptomycin 8-12 mg/kg/day IV is preferred for serious VRE infections due to bactericidal activity 2
• Linezolid 600 mg IV/PO every 12 hours for ≥8 weeks is effective for vancomycin-resistant enterococcal CNS infections 2, 3, 4, 5
  • Linezolid achieves excellent CSF penetration (60-70% of serum levels) 3, 4, 5
  • Monitor for hematological toxicity with prolonged use 2
  • Pediatric dosing requires more frequent administration (every 8 hours) due to increased clearance 4

Role of Intrathecal Antibiotics

Intrathecal antibiotics are not routinely recommended due to insufficient evidence and potential neurotoxicity 2:

• There is insufficient evidence to recommend routine intrathecal antibiotics when infected hardware is removed 2
• Intraventricular vancomycin (10 mg/24h) can cause significant neurotoxicity, including markedly elevated CSF protein levels (>3000 mg/dL) and eosinophilia 6
• Intrathecal quinupristin-dalfopristin has been used successfully for VREF ventriculitis in case reports 7
• The primary treatment effect comes from shunt removal rather than intrathecal therapy 2

CSF Monitoring and Criteria for Shunt Reimplantation

Monitor CSF parameters closely to guide timing of shunt reimplantation:

• Obtain CSF for cell counts with differential, glucose, protein, Gram stain, and bacterial cultures 1
• Process CSF within 30-60 minutes of collection for optimal results 1
• Continue antibiotics until CSF is sterile and inflammatory parameters normalize 1
• Bacterial ventriculitis typically shows: CSF glucose ≤35 mg/dL, CSF:blood glucose ratio 0.23, protein ≥220 mg/dL, ≥2,000 WBC/μL, or ≥1,180 neutrophils/μL 1
• Only reimplant a new VP shunt after achieving documented CSF sterility 2, 1

Management of Moyamoya-like Vascular Changes

The moyamoya-like angiographic changes represent secondary infectious vasculopathy, not primary vasculitis:

• These vascular changes are a consequence of the infectious process and typically improve with successful treatment of the underlying infection
• Do NOT initiate immunosuppressive therapy (corticosteroids, cyclophosphamide, rituximab) as this would be contraindicated in active bacterial infection
• The neutrophilic CSF profile (72% neutrophils), markedly low glucose (17 mg/dL), and elevated protein (334 mg/dL) are atypical for PACNS and strongly suggest bacterial infection 1
• PACNS typically presents with lymphocytic pleocytosis, not neutrophilic predominance
• Serial imaging may be warranted after infection resolution to document improvement of vascular changes

Critical Pitfalls to Avoid

Common errors that compromise outcomes:

• Never attempt to treat VP shunt infection with antibiotics alone while leaving the shunt in place – this approach has significantly lower success rates 2, 1
• Do not reimplant a new shunt before achieving CSF sterility – this leads to reinfection 2, 1
• Avoid initiating immunosuppression for presumed PACNS without excluding infection first – neutrophilic CSF with low glucose strongly suggests bacterial etiology 1
• Do not rely solely on initial negative CSF Gram stain and cultures – broad-range bacterial PCR may be necessary as demonstrated in this case 1
• Monitor for vancomycin neurotoxicity if using intraventricular administration – watch for rising CSF protein and eosinophilia 6
• Consider preoperative antibiotics for new shunt placement to prevent reinfection 1

Duration of Therapy

Total antibiotic duration depends on organism and clinical response:

• Minimum 21 days of appropriate antibiotics after achieving CSF sterility for gram-negative infections 1
• 6 weeks total therapy for enterococcal infections based on endocarditis guidelines, which may apply to prosthetic device infections 2
• Continue therapy until CSF inflammatory markers normalize and cultures remain negative 1
• Some experts extend therapy to 8 weeks for complex infections involving prosthetic devices 2