Surgeons in the operating room must achieve a delicate balance when removing a brain tumor: eradicate as much of the cancer as possible, and avoid injury to parts of the brain responsible for motor control, speech, and more.
For years, doctors have been using brain mapping – that is, stimulating the brain with electrodes to create a map of various brain functions – to identify ideal areas for tumor removal. While traditional brain-mapping methods have been crucial to reducing post-surgical deficits and improving patient quality of life, key challenges remain. For example, current electrostimulation techniques record the activity of the gray matter near the surface of the brain (the cortex) while less is known about activity in the white matter below it (the subcortex). Both the cortex and subcortex contain areas important to brain function.
New work being done at Mayo Clinic’s Florida campus aims to look deeper. A multidisciplinary team of investigators including William Tatum, D.O., Kaisorn Chaichana, M.D., Alfredo Quinones-Hinojosa, M.D., and colleagues is looking at innovative ways to collect data from the hard-to-read white matter. The researchers’ most recent focus is on glioma, a common type of brain cancer that can be aggressive. “Surgeries to remove glioma generally involve white matter, but this has been tricky to map,” says Dr. Tatum. “We think our updated technologies will help us see the connections beneath the surface of the brain.”
The researchers are working to determine whether new electrostimulation devices with a deeper reach can be used to better define which parts of the subcortex are most essential to important functions, reducing the risk of adverse outcomes.
Accurate white-matter mapping would also allow surgeons to remove a larger proportion of primary brain tumors including gliomas. “The extent of resection would have a direct effect on life expectancy,” Dr. Tatum says. “And with more than 12,000 new patients diagnosed with glioblastoma (the most aggressive type of glioma) annually, that’s a big deal.”
“In the past, standard commercially available electrodes have been available in a very restricted repertoire, in linear strips or grids placed on the brain,” says Mayo neurologist and project collaborator Anthony Ritaccio, M.D. “My Mayo colleagues have developed new electrode arrangements that are ingenious and ergonomic, but also so basic and practical that you wonder why no one has thought of them before.”
New electrostimulation devices are just part of the brain-mapping innovations underway at Mayo. Dr. Ritaccio and colleagues are also looking at ways to improve how brain activity recordings are interpreted. “We’re learning that passive recordings of brain activity can lead to a remarkably better understanding of areas of the brain responsible for tasks like listening and speech,” he says. For instance, researchers are finding that they can record brain signals of a person reading aloud, and decode the data to create speech from a prosthetic voice. “Our current work will be able to utilize Mayo’s new advancements in brain mapping to create a superior environment for understanding our electrostimulation data,” says Dr. Ritaccio.
“Electrostimulation has been used for the last half century, and it’s always had its benefits and drawbacks,” he continues. “We’re working together at Mayo to make it better, faster, and safer for patients.”