Which route is used to deliver chemotherapy directly into the central nervous system to treat brain tumors?

• A. Intravenous
• B. Intrathecal
• C. Intra-arterial
• D. Intravesicular

Answer: (B)

Delivering chemotherapy directly into the central nervous system is done through intrathecal administration. This route introduces the drug straight into the cerebrospinal fluid, typically via a lumbar puncture or an implanted reservoir, so the medicine reaches the brain and spinal cord in high local concentrations. It bypasses the blood-brain barrier, which often prevents adequate drug levels from reaching CNS tumors when given systemically. This approach is specifically used for brain tumors and conditions like leptomeningeal involvement with agents such as methotrexate or cytarabine. The other routes don’t place the drug into the CSF: intravenous goes into the bloodstream and the brain is protected by the BBB; intra-arterial targets brain tissue but doesn’t reliably deliver into the CSF; intravesicular delivers medication into the bladder, not the CNS.