For epilepsy, a microelectrode array with big promise
Date: May 3, 2012
Doctors have made great strides in developing better ways to understand and treat epilepsy. Generally, these advances rely on finding the “focus,” the point where the abnormal storm of electrical activity that sparks a seizure starts in the brain. But in some people, the usual method to track down the focus—stretching a network of sensors across the scalp—isn’t informative.
“It’s not always accurate, even to the point that it’s hard to tell which side of the brain seizures are coming from,” says neurosurgeon William S. Anderson.
Anderson, who earned a Ph.D. in physics before realizing that his true calling was joining the very physics-oriented field of treating epilepsy, explains that the second best option—placing electrical recording elements directly on the brain’s surface—can also be misleading. Each electrode is more than 2 millimeters wide. Though tiny, this size is orders of magnitude larger than the smallest brain cell bodies, which average just a handful of microns across. Additionally, spacing between electrodes in the grids that are widely used to monitor electrical activity is about 1 centimeter. Consequently, Anderson says, these electrode grids take recordings from large groupings of cells but miss other swaths of cells that might contain the focus.
“My colleagues and I thought we might be able to learn more about epilepsy and the way seizures evolve across the brain surface if we could monitor electrical activity using even smaller recording elements,” he says.
Luckily, technology recently caught up with their research hopes in the form of new recording elements that fit tens of separate electrodes into the space of a single electrode used in the past. By snapping these microelectrodes into a grid, the researchers can sample the electrical activity of just a handful of pinpointed brain cells at a time, allowing them to look for abnormal activity with far higher accuracy.
Right now, Anderson and his colleagues are using this system to learn more about how brain cells connect and interact—information that could shed light not only on diseases such as epilepsy, but on how healthy brains perform complex cognitive tasks such as dredging up memories, causing parts of the body to move, and facilitating speech and hearing. Eventually, he says, researchers can use what they learn about the brain to develop more targeted ways of treating epilepsy, chronic pain and other abnormalities that originate in this still-mysterious organ. For example, in the future, doctors might be able to focus electrical stimulation to disrupt abnormal electrical activity on just a handful of cells or remove even tinier snippets of anomalous tissue than current technology allows.
“As we better define the volume of tissue affected by seizures and other disorders,” Anderson says, “we can develop tailored therapies to serve our patients even better.”
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