Medicine by Design: The Practice and Promise of Biomedical Engineering

CHAPTER 6. The Wires

Chapter 6 The Wires Acure for Laszlo Nagy’s underlying paralysis may still be a long way off. But using electricity to tackle a host of medical problems is gaining momentum. P. Hunter Peckham, J. Thomas Mortimer, and their colleagues are taking the techniques they developed for spinal cord injury patients and applying them to other conditions, such as incontinence, stroke-related paralysis, and obstructive sleep apnea. One of the most intriguing frontiers of electrical stimulation,however , is in the body’s most complex organ, the brain. A confluence of rapidly evolving developments—researchers’ expanding knowledge of how the brain works, more precise imaging, and the development of ultrathin electrodes that can be implanted in the brain—has made brain stimulation, or pacing, a hot field. To date, the most progress has been made in treating movement disorders, such as Parkinson’s and essential tremor. One of the nation’s leading practitioners of brain pacing for Parkinson’s is a surgeon at the Cleveland Clinic, Ali Rezai. Since 1997, he has implanted electrodes in the brains of more than 500 patients, most of whom had Parkinson’s. The procedure, known as deep brain stimulation (DBS), is time consuming, requiring precise imaging and brain mapping. Picking a skilled surgeon is key. But DBS has proved to be highly effective, substantially reducing tremors in an overwhelming majority of people. Rezai,who collaborates with biomedical engineers from the Cleveland Clinic and neighboring Case Western Reserve University, is con-
fident that the use of deep brain stimulation for a wide variety of physical and psychiatric ailments is on the verge of rapid growth. The important thing is to identify centers of the brain that control different functions and then apply the proper charge—high frequency or low frequency, pulsating or steady—to counteract or block the malady. Researchers are now experimenting with ways to use DBS to prevent epileptic seizures, and Rezai thinks the technique could be used for pain control, autism, or improving function in people who have had strokes. On the psychiatric front, preliminary tests show that DBS may be helpful in treating obsessive-compulsive disorder. Rezai said that the technique may one day be used as a therapy for depression, addiction, and schizophrenia. “Treating Parkinson’s is just the tip of the iceberg,” Rezai told me. “The future is very bright, and we can help many patients. This technique is evolving rapidly and will be coming on strong in the next decade. Think of it as being at a stage where heart pacemakers were in the 1960s.” Biomedical engineers are pushing the boundaries of brain research even further. Dawn Taylor, a biomedical engineer at Case and the Cleveland Veterans Administration Hospital, is one of a small group of investigators around the country making steady progress on a far-fetched dream: using an incapacitated person’s thoughts to direct movement. By implanting an array of electrodes in a monkey ’s brain and then analyzing the firing of brain cells as the monkey moves, Taylor and others have succeeded in allowing a monkey to control a computer cursor simply by thinking about it. The goal is to enable people like Laszlo Nagy to move a robot arm, or an electrically stimulated muscle in a paralyzed arm, using only the firing of neurons in their brain. Some researchers are already beginning preliminary trials with people who have amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, a degenerative nerve condition that eventually causes complete paralysis and death. “We’re looking at all kinds of options of how to move this into clinical reality,” said Taylor. “Our goal in five years is to have it for ALS patients.” THE WIRES 63 64 MEDICINE BY DESIGN One of the biggest medical engineering successes in recent years has been the development of the cochlear implant, which uses an array of electrodes, speech processors, and transmitters to convey rudimentary sounds to the brains of deaf people. In the United States alone, more than 13,000 adults and 10,000 children have received cochlear implants. On a far more experimental level, researchers are trying to restore sight to the blind by using tiny cameras mounted on eyeglasses and semiconductor chips at the back of the person’s eye to transmit visual signals to the brain. A device that actually restores some semblance of sight is years away, but the concept has promise and may one...