Chemotherapy uses drugs to kill the cancer cells and prohibits their growth. Chemotherapy is not a very efficient mode of treatment for brain tumors, also called glioma. This is because the chemotherapy drugs are unable to enter the barrier formed by the central nervous system. The capillary cells of blood vessels that pass through the brain permits only selective chemicals to enter inside the brain. Owing to chemotherapy and blood brain barrier, most of the chemotherapy drugs cannot reach the brain; this has led the researchers to find some new drugs and methods of treatment.

The blood brain barrier is formed by endothelial cells lining the blood capillaries that traverse the brain. These endothelial cells are tightly knit and permit very tiny and selected particles to enter the brain. Thus the Trans cellular movement of the chemo molecules depends on the permeability of endothelial cells. So when chemotherapy treatment is used to cure cancer of the central nervous system, blood brain barrier does not allow the drugs to become effective, as they cannot enter the barrier. Following an intravenous injection these chemotherapy drugs fail to maintain adequate osmotic balance to pass the tightly interlocked endothelial cells. Researchers are coming up with a variety of novice techniques to break the chemotherapy and blood brain barrier. Some most frequently used methods include:

1. Use of high dose of chemotherapy drugs to concentrate more chemo particles outside the walls of the blood capillaries. This would stimulate the endothelial cells to open and permit the entrance of chemotherapy drugs inside the brain.
2. Use of Chemotherapy Wafers: Chemotherapy wafers are implanted after the surgery at the site of the tumor. These wafers, also known as gliadel wafers, dissolve over a period of 2-3 weeks to cure the residual cancer cells.
3. Intrathecal Chemotherapy : In lumber puncture and intrathecal chemotherapy, the chemotherapy drugs directly to the spinal fluid.
4. Convention enhanced delivery or CED involves placing a catheter into the brain tumor or nearby brain tissue to deliver the drug into the brain. This procedure is very slow and continues for several days.
5. Induction of hyperosmolarity solutions are also given so that the drugs are able to break this barrier.

Since the blood brain barrier holds back the chemotherapy drugs, systemic delivery of these drugs does not prove fruitful. In early 1980s Edward A. Neuwelt, M.D., a neurosurgeon of OHSU, devised a new mechanism to overcome the blood brain barrier. This mechanism uses concentrated sugar solution to shrink the endothelial cells thus widening the intracellular voids for the passage of large size chemotherapy drugs. This technique is coined as bloodbrain barrier disruption or BBBD. Use of BBBD technique has allowed the passage of chemotherapy drugs to the site of tumor and thus increases the efficacy of the treatment manifolds. Thus, oncologists these days know how to deal with chemotherapy and blood brain barrier and the various treatments given are quite well tolerated by most of the patients.