Friday, May 29, 2009

Deep Brain Stimulation

In Chapter 7 of the 4th Edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I describe electrical stimulation (Section 7.10, pages 192-196), including excitation of peripheral nerves (Problems 7.38-7.41) and cardiac pacemakers. Another increasingly important procedure is Deep Brain Stimulation. On May 21, Medtronic announced Food and Drug Administration approval of two new models of the Activa stimulator for use in the United States to treat Parkinson's disease and essential tremor. This device is similar to a pacemaker, but electrodes are implanted in the brain instead of the heart. The detailed electrophysiological mechanism is still unknown, but repetitive stimulation of certain structures deep in the brain provides dramatic relief to some patients with movement disorders. The new Activa RC and PC stimulators have features not available in older models, such as the RC's rechargeable battery.

A friend of mine, Frans Gielen, has worked on deep brain stimulation at the Medtronic Bakken Research Centre in Maastricht, the Netherlands. Frans was a post doc when I was a graduate student at Vanderbilt University, working in the laboratory of John Wikswo; we both worked on measuring the magnetic field of nerves and muscle fibers (for instance, see Gielen, Roth and Wikswo, Capabilities of a Toroid-Amplifier System for Magnetic Measurement of Current in Biological Tissue, IEEE Transactions on Biomedical Engineering, Volume 33, Pages 910-921, 1986). Frans is considered at Medtronic as "the architect of the Medtronic Activa Tremor Control Therapy". Known fondly while in Wikswo's lab as "that crazy Dutchman," when he left Vanderbilt we were not surprised that Frans would make important contributions to Medtronic.

For more about deep brain stimulation, two review articles are Deep Brain Stimulation for Parkinson's Disease (Benabid AL, Current Opinion in Neurobiology, Volume 13, Pages 696-706 2003) and Uncovering the Mechanism(s) of Action of Deep Brain Stimulation: Activation, Inhibition, or Both (McIntyre CC, Savasta M, Kerkerian-Le Goff L, Vitek JL, Clinical Neurophysiology, Volume 115, Pages 1239-1248, 2004).

For those wanting to read about deep brain stimulation from the patient's perspective, see
Deep Brain Stimulation: A New Treatment Shows Promise in the Most Difficult Cases by Jamie Talan. In the Prologue, Talan writes
"On March 14, 1997, the U.S. Food and Drug Administration held a hearing on the use of deep brain stimulation (DBS) as a treatment for essential tremor and Parkinson's disease. By that time, excitement about this technology, which could restore a body to its rightful state of controlled movement, had spread through brain research laboratories and neurology clinics around the world. Desperate patients with all kinds of movement disorders had heard about deep brain stimulation, too, and they were clamoring for access to the treatment.

On this day in March, two American patients, Maurice Long and George Shafer, were standing before an advisory panel commissioned by the FDA to study the benefits and risks of deep brain stimulation. Long and Shafer were among the 83 people with essential tremor and 113 people with Parkinson's tremor who had undergone deep brain stimulation in a large clinical trial. The FDA-approved study was sponsored by Medtronic, the Minneapolis-based company that supplied the simulating electrodes for the trial. Founded in 1949 to usher in a new technology called cardiac pacing, Medtronic had made the first implantable heart pacemaker. Now the company was in the middle of an international push on another frontier: the brain seemed to be as receptive to electrical stimulation as the heart."

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