Mayo Clinic neurosurgeon Kendall H. Lee, M.D., Ph.D., is exploring how deep brain stimulation may help people with neurological-based movement disorders.
An implantable device may help people with neurological disorders regain their lives
"Can I show you something?" the researcher asks. Before anyone responds, his fingers quickly tap away at the computer. On his screen, a video frame paused on a lab rat appears.
"It's been paralyzed for weeks," explains Kendall H. Lee, M.D., Ph.D., a neurosurgeon at Mayo Clinic in Minnesota. He clicks the play button, and the rat's right leg jolts to life. He plays more clips. In one, a leg slowly rises and falls. In another, both legs alternate movement, mimicking a swimmer's kick.
"It's not just twitch," he says. "We're controlling this wirelessly."
Imagine losing control of your body. Your limbs twitch. Your face contorts. You pick up a glass of water for a drink, but your hand shakes it empty. Unfortunately, for people with neurological disorders and psychiatric disorders, lack of control is central to their everyday lives.
One treatment strategy to help people with neurological-based movement disorders, such as Parkinson's disease, regain control over their bodies is deep brain stimulation (DBS). Electrodes implanted deep within the brain deliver mild pulses that stimulate the release of neurotransmitters, or chemicals, that activate neurons, the brain's message carriers.
"It's as if DBS is controlling the brain's pharmacology, the neurotransmitters in your brain that you're already making," explains Dr. Lee, a specialist in DBS. After DBS helps neurons resume normal communication with each other, disease symptoms subside.
Though often successful, the therapy has some drawbacks. During the surgical procedure, for instance, the patient must remain awake, and many patients are understandably hesitant to undergo brain surgery while conscious. But current DBS systems are an open loop, meaning that during surgery and follow-up recalibration sessions, physicians must rely on visible symptoms and the patient's subjective feedback — when I apply this stimulation, does speech improve? Do tremors lessen? No? Then let's try this ...
This inexactness and inefficiency stand between DBS and its use for other neurological and psychiatric disorders, especially those that cause pain, mental and emotional distress, and other nonvisible conditions that are difficult to measure.
Dr. Lee and his colleagues in Mayo Clinic's Neural Engineering Lab think they have found a better answer. The team is developing a "smart" DBS system that wirelessly monitors and measures neurotransmitters and uses concrete biological feedback to deliver precise stimulation.
"We're now combining the technology with our knowledge of biology, and making the biology better," Dr. Lee says.
The challenge is building implantable wireless circuitry advanced enough to match the brain's sophistication. But Mayo's interdisciplinary approach is uniquely poised to succeed. It combines the neurosurgery team's medical skill with Mayo's expertise in engineering and microchips. Not many people realize that Mayo Clinic has its own Division of Engineering, chaired by Kevin E. Bennet, whose job is to design devices, systems and instruments that aren't available commercially. In other words, they custom-make tools to help patients.
Working with Dr. Lee and his group, the engineers are developing wireless sensor and neurostimulator prototypes, which will use integrated circuitry custom designed by Mayo's Special Purpose Processor Development Group, led by Barry K. Gilbert, Ph.D.
The collaboration already reached a significant clinical milestone last year with its Wireless Instantaneous Neurotransmitter Concentration Sensing (WINCS) system, a device that tracks real-time neurostransmitter changes in the brain. In an early phase clinical trial, it successfully recorded, wirelessly, the release of neurotransmitters in 15 Parkinson's and essential tremor patients undergoing DBS surgery.
"With WINCS, we're now seeing for the first time what is changing in the brain," Dr. Lee says. "It's really exciting, because now imagine — if we could take advantage of that knowledge — the type of things we can do with deep brain stimulation."
Dr. Lee's group is already finding out with the Mayo Investigational Neuromodulation Control System (MINCS), a wirelessly controlled neurostimulation device optically linked to WINCS. Researchers are using the implantable device in animal models to deliver precise brain stimulation wirelessly. It was the MINCS device that moved the leg of Dr. Lee's paralyzed rat.
The next generation
"Isn't that gorgeous?" Dr. Lee asks, admiring a picture of WINCS Harmoni.
It's the observation of a true scientist. To the untrained eye, WINCS Harmoni resembles a small circuit board pulled from a cellphone, but Dr. Lee sees its limitless possibilities — a smart, self-contained, implantable DBS system. Now in prototyping stage, WINCS Harmoni combines WINCS, MINCS and a complex algorithm that translates the biological feedback from WINCS into precise stimulation patterns delivered by MINCS.
As Dr. Lee describes the relationship between sensors, circuitry and science, he oddly passes on describing their interplay as "harmonious," an expected riff on the system's name. Realizing this, he pauses.
"By the way," he says, "Harmoni is not for 'harmonious.' It's the Korean word for 'grandmother,' my way of honoring someone who's caring."
It's an apt distinction. Technological wizardry aside, WINCS Harmoni is meant to treat people and in many cases provide relief to families. Through smart DBS therapy, people with complex psychiatric disorders, unmanageable pain, spinal cord injuries, memory loss and a host of other difficult-to-treat disorders have hope — all because, as Dr. Lee puts it, Mayo has the tools to understand and control what's happening in the brain and spinal cord.
"My hope," he says, "is that this will open up a new era in medicine. If you look at all the medications we use that somehow affect the chemistry in the brain, we are now in an era where we can control the systems even better. So rather than going the 'shotgun approach' of medicine, we can go with the smart systems of DBS."
Mayo's Neural Engineering Lab hopes to test WINCS Harmoni in patients this year.