Miniature implanted devices could treat epilepsy, glaucoma

Purdue University researchers have developed new miniature devices designed to be implanted in the brain to predict and prevent epileptic seizures and a nanotech sensor for implantation in the eye to treat glaucoma.

Findings will be detailed in three research papers being presented at the Engineering in Medicine and Biology Society’s Sciences and Technologies for Health conference from Aug. 23-26 in Lyon, France.

One research project focuses on a tiny transmitter three times the width of a human hair to be implanted below the scalp to detect the signs of an epileptic seizure before it occurs. The system will record neural signals relayed by electrodes in various points in the brain, said Pedro Irazoqui (pronounced Ear-a-THOkee), an assistant professor of biomedical engineering.

“When epileptics have a seizure, a particular part of the brain starts firing in a way that is abnormal,” Irazoqui said. “Being able to record signals from several parts of the brain at the same time enables you to predict when a seizure is about to start, and then you can take steps to prevent it.”

Data from the implanted transmitter will be picked up by an external receiver, also being developed by the Purdue researchers.

The most critical aspect of the research is creating a device that transmits a large amount of data at low power. The transmitter consumes 8.8 milliwatts, or about one-third as much power as other implantable transmitters while transmitting 10 times more data. Another key advantage is that the transmitter has the capacity to collect data specifically related to epileptic seizures from 1,000 channels, or locations in the brain, Irazoqui said.

“The fact that this circuit can deliver such a vast amount of data and, at the same time, be less power hungry than anything else that’s out there is what makes this important,” he said.

A paper about that work will be presented during the conference on Aug. 26. The paper was written by doctoral student Eric Chow, undergraduate student Adam Kahn and Irazoqui, all in the Weldon School of Biomedical Engineering.

While the transmitter and its battery are to be implanted below the scalp, the electrodes that pick up data will be inserted directly in the brain through holes in the skull and then connected to the transmitter by wires.

A commercial implantable device developed by other researchers for epilepsy currently is in clinical trials at several sites, including the Indiana University School of Medicine.

“That device can record from eight channels to collect epilepsy data, compared to a thousand channels for our system,” Irazoqui said. “The more parts of the brain that you can look at simultaneously, the better you are able to predict the seizure onset, so the number of channels has a direct correlation with how well the device works.”

The research has been funded by Chicago-based Citizens United for Research in Epilepsy, known as CURE. Irazoqui’s research group also recently received a two-year grant from the Wallace H. Coulter Foundation to further develop the technology.

“We are planning on doing human testing in two years,” Irazoqui said. “Epilepsy affects about 1 percent of the global population, and of that 1 percent, 30 percent don’t respond to any drugs. There is no cure or treatment for those 30 percent.”

New technologies being developed aim to change that by predicting the onset of seizures and immediately dispensing a chemical called a neurotransmitter directly to the area of the brain where the seizure is starting.

The Purdue researchers will work with Dr. Robert Worth, a neurosurgeon at the IU School of Medicine.

The system’s high performance is made possible by simultaneously reducing power consumption and electronic interference. The researchers also calculated how well the signals are transmitted through tissue.

“We looked at the equivalent of the amount of skin that you have on your scalp, which is about 2 or 3 millimeters,” Irazoqui said. “We have demonstrated that the transmitter does penetrate the thickness of tissue that would be required for this application.”

The smaller the power consumption, the smaller the battery, which is critical for implantable devices. The battery in the Purdue device is about the size of a nickel. The signals are amplified, digitized and transmitted to the external receiver.

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