Scientists, for the first time, have non-invasively opened the blood-brain barrier (BBB) in a patient.
A team at Sunnybrook Health Sciences Centre in Toronto, led by neurosurgeon Todd Mainprize, M.D., used focused ultrasound technology to more effectively introduce chemotherapy drugs into a patient’s malignant brain tumor. The results were verified with a post procedure MRI scan.
The blood-brain barrier keeps toxins in the bloodstream away from the brain. It consists of a tightly packed layer of endothelial cells that wrap around every blood vessel throughout the brain. It prevents the passage of viruses, bacteria and other toxins, while ushering in vital molecules such as glucose via specialized transport mechanisms.
The downside of this is that the blood-brain barrier also blocks the vast majority of drugs. There are a few exceptions, but those drugs that are able to sneak through can also penetrate every cell in the body, which makes for major side effects.
To breach the BBB, doctors infused a chemotherapy drug, along with tiny gas-filled bubbles, into the blood stream. Then focused ultrasound was applied to the tumor and surrounding brain, causing the bubbles to vibrate, and open the BBB so high concentrations of the chemotherapy could enter targeted tissues.
The team confirmed that the blood-brain barrier had been breached by injecting a harmless contrast agent called gadolinium into the patient. Gadolinium cannot normally cross the barrier, says Mainprize. However, MRI scans clearly showed that the areas disrupted by the ultrasound contained gadolinium after the treatment, demonstrating that the blood-brain barrier had opened, he says.
Image: Dr. Todd Mainprize shows where the blood-brain barrier opened.
Last week, the procedure was trialed on the first of ten subjects with brain tumors, a middle-aged woman. 24 hours after the breach was initiated, the tumor and the surrounding tissues were sampled and removed surgically, then sent to a laboratory to examine how much of the medication reached the target areas.
If this trial proves to be effective, safe, and feasible, this non-invasive technique will revolutionize neurosurgery, and not just for cancer treatments: Alzheimer’s disease is another target for this ultrasound-based method, and already, in-roads are being made.