by Paul Pyzowski, Guest Contributor
I had recently written an article here on the use of MEMS in neuroscience research applications, and Colin Johnson penned a separate article on how MEMS are enabling systems to restore sight for the blind. This article focuses on the increasing use of MEMS for treating diseases and injuries of the central nervous system (brain and spine), including paralysis, Parkinson’s disease, and drug-resistant depression.
As background, according to Zack Lynch at the Neurotech Industry Organization, medical devices for treatment of nervous system disorders is a $7 billion market. Although small compared to the $120 billion market for neuropharmaceuticals, the neuro-device market is growing at 15% per year and is considered a real growth market, albeit one with considerable investment requirements and considerable risk.
The concept of using electricity to treat diseases of the nervous system goes back several centuries; American founding father and inventor Benjamin Franklin published a paper proposing to use electricity to treat paralysis. Today’s neuromodulation devices are accepted medical therapies, and MEMS and microfabrication technologies are being incorporated into new products.
In deep brain stimulation (DBS), electrodes are surgically implanted in the brain.
Conceptually, neuromodulation devices are pacemakers for the nervous system, consisting of an external or implanted pacing unit with electronics and a battery, along with one or more electrodes to deliver an electrical stimulus to a specific target in the nervous system. Examples of therapies include spinal cord stimulation for chronic pain, vagus nerve stimulation for epilepsy, and deep brain stimulation for Parkinson’s disease. For some therapeutic areas, stimulation electrodes adapted from cardiac pacing are sufficient. For others, MEMS based microelectrodes enable substantially more precise, carefully controlled and continuously monitored electrical stimulation.
One MEMS based system for neuromodulation was originally developed by the company Cyberkinetics for quadriplegics “to communicate and control common every-day functions literally through thought”. With this device, a Utah-style MEMS electrode array was implanted in the brain to record motor signals then used to move a cursor on a computer screen; the ultimate goal was to enable the control of actual or prosthetic limbs. Cyberkinetics unfortunately went out of business in 2009, although a successor company named the Braingate Company continues clinical development.
A Utah-style MEMS electrode array used in the Braingate system for quadriplegics.
A patient with the Braingate system.
Nearly 75,000 people worldwide who suffer from Parkinson’s disease have been treated with deep brain stimulation (DBS), in which an electrode is surgically implanted in the brain to eliminate the involuntary debilitating tremors and rigidity associated with the disease. Clinical studies have shown that DBS is more effective than drugs in treating Parkinson’s; however due to the long surgical times and high rate of complications and side-effects, DBS is considered a therapy of last resort. Several academic groups, including Jack Judy’s group at UCLA, the Philipe Renaud lab at the Swiss Federal Institute of Technology, and IMEC in Belgium have been developing MEMS based DBS electrodes that should greatly reduce if not eliminate these known drawbacks.
The success of DBS for Parkinson’s disease and other movement disorders has encouraged others to look at similar treatments for cognitive disorders including epilepsy, obsessive-compulsive disorder, and drug resistant depression. As a rule, cognitive disorders are treated with electrodes “on”, not “in” the brain, and can also require both sensing and stimulation electrodes. Developing these products is long and costly – Neuropace took nearly a decade to prove its epilepsy treatment, and Northstar Neuroscience spent over $100 million before shutting down after a failed clinical trial in stroke rehabilitation.
A recent and exciting innovation is the use of flexible microfabricated electrode arrays that can be placed directly on the brain. Researchers at the University of Illinois-Urbana, Tufts University, and the University of Pennsylvania fabricated and tested electrode arrays fabricated on a silk-like substrate that conforms to the surface of the brain and dissolves over time, thus leaving behind the electrodes only. This may open the door to future therapies for the millions of people who suffer from otherwise intractable neurological conditions.
Paul Pyzowski is an entrepreneur and executive whose experience in MEMS includes DNA diagnostics, medical devices for treatment of neurological disease, chemical sensors for both homeland security and clean energy, and electronic design automation. He can be reached at [email protected].
Copyright 2010 MEMS Investor Journal
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