What is the recommended management for central nervous system blastomycosis?

Management of Central Nervous System Blastomycosis

For CNS blastomycosis, initiate treatment with liposomal amphotericin B at 5 mg/kg per day for 4-6 weeks, followed by prolonged oral azole therapy (voriconazole, fluconazole, or itraconazole) for at least 12 months. 1

Initial Induction Therapy

• Start with lipid formulation amphotericin B at 5 mg/kg per day for 4-6 weeks as the preferred initial treatment 1
• Liposomal amphotericin B is specifically preferred over other lipid formulations because it achieves higher CNS levels in animal models of fungal meningitis 1
• Amphotericin B deoxycholate (0.7-1 mg/kg per day) is an alternative if lipid formulations are unavailable, though it carries greater toxicity 1
• Never use azoles as primary monotherapy for CNS blastomycosis—they should only be used as step-down therapy after initial response to amphotericin B 1

Step-Down Oral Azole Therapy

After completing 4-6 weeks of amphotericin B and demonstrating clinical improvement, transition to oral azole therapy for at least 12 months: 1

Azole Options (in order of preference based on CNS penetration and activity):

Voriconazole (200-400 mg twice daily):

• Offers excellent CSF penetration combined with strong intrinsic activity against Blastomyces dermatitidis 1
• Recent case series demonstrate successful outcomes with voriconazole for CNS blastomycosis 2, 3, 4
• Emerging as the preferred azole based on pharmacologic properties and clinical experience 2, 3

Fluconazole (800 mg daily):

• Provides excellent CSF penetration but has less intrinsic activity against Blastomyces compared to other azoles 1
• Supported by anecdotal reports of success 1
• Reasonable option when other azoles are not tolerated 5

Itraconazole (200 mg 2-3 times daily):

• Has greater intrinsic activity against Blastomyces than fluconazole but achieves minimal CSF levels 1
• Few case reports document success in CNS disease 1
• Monitor serum itraconazole levels after 2 weeks to ensure adequate drug exposure 1

Duration and Monitoring

• Continue azole therapy for at least 12 months and until resolution of CSF abnormalities 1
• Immunosuppressed patients may require longer treatment duration 1
• The 2021 global guideline recommends more prolonged courses for CNS involvement based on relapse patterns in case series 5

Diagnostic Considerations

• Most patients present with headache, confusion, or focal neurological deficits 1
• In immunosuppressed patients with disseminated blastomycosis, perform brain imaging even without CNS symptoms to assess for occult CNS involvement 1
• MRI is superior to CT for detecting CNS lesions 2, 3
• CNS manifestations include meningitis, intracranial mass lesions, epidural abscess, or combinations thereof 3

Surgical Intervention

• Consider neurosurgical drainage for epidural abscesses or mass lesions causing focal neurological dysfunction 1
• Surgery may be critical in limiting morbidity and mortality when focal lesions cause significant mass effect 1

Common Pitfalls to Avoid

• Do not start with azole monotherapy—this is associated with treatment failure in CNS disease 1
• Do not use standard amphotericin B dosing (3-5 mg/kg) for CNS disease—the higher dose of 5 mg/kg is specifically recommended 1
• Do not discontinue therapy prematurely—CNS blastomycosis requires prolonged treatment (minimum 12 months total) to prevent relapse 1
• Avoid assuming adequate itraconazole exposure without checking serum levels, as absorption is variable 1

Special Populations

• Pregnant women: Use lipid amphotericin B formulation at 3-5 mg/kg per day; avoid all azoles during pregnancy 1
• Immunosuppressed patients: May require lifelong suppressive therapy with itraconazole 200 mg daily if immunosuppression cannot be reversed 1