Cerebral aspergillosis: tissue penetration is the key.

Cerebral aspergillosis is increasingly recognized in severely immunocompromised patients and, until recently, this type of fungal infection was associated with a mortality approaching 100%. The central nervous system is a protected environment and penetration of drugs across the blood-brain barrier is mainly limited by their molecular size and physicochemical properties, as well as drug interaction with transporter systems (e.g., P-glycoprotein) at the blood-brain barrier. Most antifungal agents are large molecules (>700 Da), which makes sufficient penetration into the central nervous system unlikely. In fact, the available data indicate low levels of most antifungal agents in cerebrospinal fluid and brain tissue, except for fluconazole and voriconazole. Concentrations of voriconazole exceeding inhibitory concentrations for Aspergillus species were found repeatedly in cerebrospinal fluid and brain tissue, including brain abscess material. A recent retrospective study confirmed that voriconazole treatment resulted in improved response and survival rates in patients with cerebral aspergillosis. Data from animal models, which explored escalated doses or combinations of antifungal agents in experimental neuroaspergillosis, suggest that selected combination or dose-escalated therapies might further improve the still unsatisfactory prognosis in this particular type of Aspergillus infection.