Could an implanted “brain pacemaker” be the key to stimulating memory functions in people with Alzheimer’s disease?
Forget antiquated notions of crude “shock therapy.” Electrical energy—usually in the form of deep brain stimulation, or DBS—is being harnessed for its potential to treat a wide range of conditions, from tremors and chronic pain to obesity and depression. DBS has already proven highly effective in treating motor tremors associated with Parkinson’s disease, and now, scientists are testing its ability to stimulate memory circuits in people with Alzheimer’s.
Deep brain stimulation is nothing like those old sci-fi-movie images of hapless patients strapped down in a chair with electrodes all over their heads. DBS techniques are a lot more subtle, and definitely more high-tech. Essentially, a tiny hole is drilled into the skull, and the surgeon passes a small wire with an electrode at its tip directly into the desired location within the brain, says Dr. Richard Selenick in an article for The Atlantic. The wire is attached to a small battery-powered device called an implanted pulse generator (IPG) that controls the stimulating electrode. The IPG is then implanted under the skin near the collarbone, and the patient can turn it on and off themselves using a controller.
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Though scientists haven’t pinpointed the exact mechanism by which DBS works, they do know that the electrical impulses can be used for various purposes, including inhibiting cells from firing or making neural circuits more active. It’s the latter that has potential in the treatment of Alzheimer’s.
So far, one of the most promising outcomes for DBS treatment has been in suppressing the tremor symptoms of Parkinson’s disease. According to a CBS News article, “Between 85,000 and 100,000 people around the world have had DBS to block the tremors of Parkinson’s disease and other movement disorders.” Overactive nerve cells are quieted by the jolts of electrical energy, and there are very few side effects due to the precision of the technique.
A 2012 study in Neurology showed that even after 36 months, Parkinson’s patients continued to show improved motor function. However, quality of life eventually did show a decline, even after initial gains; the primary reason for this is that DBS treats symptoms, but it does not alter the course of the underlying disease. In Alzheimer’s, though, the situation may be more complicated—and there may be cause for hope that the disease itself may be alleviated by DBS.
Researchers in Canada first realized the potential of DBS for Alzheimer’s treatment back in 2003, when they were doing a study on obesity: in one subject, the electrical jolts unleashed a torrent of old memories. Over time, reports the CBS News article, the DBS also improved his ability to learn. This prompted researchers to try implanting the electrode in a memory hub called the fornix in order to test whether DBS would stimulate activity in that region. A small phase I study, conducted in 2010 on 6 patients with mild Alzheimer’s in, had promising results: activity in the memory circuit increased, and they showed a slower rate of cognitive decline.
The brain’s utilization of glucose for fuel also decreases in those with AD, and DBS was shown to reverse that trend—not only in the small 2010 study but in a more recent study by the same team in 2012. In plain English, an increase in the brain’s glucose metabolism was associated with better clinical outcomes over time: in memory and cognition as well as quality of life. Some patients even showed a “reawakening” of cognitive circuits that had been silenced by the disease. The results are extremely promising, but there’s still work to be done. The next step for scientists is to confirm the results of these preliminary studies in larger groups of people, tracking the effects of DBS over time.
If you or a loved one has undergone deep brain stimulation for Parkinson’s disease, as an Alzheimer’s treatment or treatment for another condition, we want to hear about it—leave your input in the comments below.