Convection-enhanced delivery: from mechanisms to clinical drug delivery for diseases of the central nervous system.

The evolution of cancer chemotherapy has been a major advance in medical science in the late 20th century. However, patients with malignant gliomas have not benefitted much. The blood-brain barrier (BBB), which always hinders the entry of therapeutic agents into the central nervous system (CNS), may at least partly be responsible. Convection-enhanced delivery (CED), a method for distributing large and small molecular weight compounds bypassing the BBB, enables robust distribution of the infused molecules at the site of infusion. CED is promising as an effective treatment not only for malignant gliomas but also for multiple CNS disorders because this method can effectively distribute multiple molecules that are potentially effective against different diseases. Although the method is quite simple, several problems require solution in developing novel CED-based strategies, including what, where, when, and how to infuse. This review discusses basic considerations when developing CED-based strategies for CNS diseases, focusing mainly on brain tumors.