It has been estimated that nearly 99 percent of treatments that could potentially be effective for neurological diseases such as Parkinson’s, Alzheimer’s and brain tumors cannot be used because they are blocked from entering the brain by what is called the blood-brain-barrier (BBB).

Self-defense

The BBB is necessary for normal health and functioning of the brain, but it effectively bars many potential therapies that are given by traditional methods (oral or intravenous) from access to the brain.

Physicians and scientists have worked together to devise a number of approaches to overcome the BBB, with only limited success so far. For example, there have been drugs and techniques developed to temporarily open the BBB in conjunction with intravenous administration of treatments for brain tumors; this approach has seen modest success in treating lymphoma when it occurs in the brain.

On the edge

Other approaches, which are still experimental, have focused on modifying the chemistry and structure of new drugs so that they can latch on to the transporters that bring essential nutrients (for example, sugar) to the brain. This approach does not, however, permit therapeutic delivery into the brain substance itself.

"These new technologies provide hope that myriad new treatments will become available in the very near future..."

One of the more exciting new approaches involves delivery of treatments directly into the brain itself, and there are several methods for doing this.

Chemotherapy-loaded biodegradable wafers have been used to treat some brain tumors after surgery with modest success. A more recent, and still investigational, approach involves slow injection of drugs into target sites within the brain. This technique, called convection enhanced delivery (CED), permits a wide range of conventional and novel drugs to reach specific target areas in the brain.

There are a few new types of catheters that appear to improve the reliability of delivering drugs via CED. These new technologies provide hope that myriad new treatments will become available in the very near future for patients with neurological diseases that are difficult to treat.