A pacemaker that sends continuous electrical impulses to specific regions of the brain appears to reverse the downturn in brain metabolism that typifies Alzheimer’s disease.
A pilot study on a handful of people suggests that deep brain stimulation, a therapy already used in some patients with Parkinson’s disease and depression, may offer hope for at least some with Alzheimer’s.
Alzheimer’s disease is a progressive and lethal dementia that mostly strikes the elderly, affecting memory, thinking and behavior. Experts estimate that as many as 5.1 million Americans may have Alzheimer’s — and that number is expected to skyrocket as baby boomers age.
The study was designed to establish the safety of the brain pacemaker and involved just six people, said the study’s first author, Gwenn Smith, Ph.D., a professor in the department of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine.
The research, published in the Archives of Neurology, was conducted while Smith was on the faculty at the University of Toronto, and will be continuing at Toronto, Hopkins and other U.S. sites in the future. The study was led by Andres M. Lozano, M.D., chairman of the department of neurosurgery at the University of Toronto.
Smith notes that while the study needs to be replicated on a larger scale, there is not another treatment for Alzheimer’s “that shows such promising effects on brain function.”
One month and one year after implanting a device that allows for continuous electrical impulses to the brain, Smith and her colleagues performed PET scans that detect changes in the metabolism of glucose in the brain’s cells. The scans showed that patients with mild forms of Alzheimer’s showed sustained increases in glucose metabolism, an indicator of neuronal activity. The increases were larger than those found in patients who have taken the drugs currently marketed to fight the progression of Alzheimer’s, the researchers note.
Other imaging studies have shown that a decrease in glucose metabolism over the course of a year is typical in the disease.
The researchers observed roughly 15 percent to 20 percent increases in glucose metabolism after one year of continuous stimulation. The increases were observed in patients with better outcomes in cognition, memory and quality of life. In addition, the stimulation increased connectivity in brain circuits associated with memory.
Deep brain stimulation (DBS) requires surgical implantation of a brain pacemaker, which sends electrical impulses to specific parts of the brain. For the study, surgeons implanted a tiny electrode able to deliver a low-grade electrical pulse close to the fornix, a key nerve tract in brain memory circuits.
The trial came about when Lozano used DBS on the fornix to treat an obese man. The procedure, designed to target the regions of the brain involved in appetite suppression, unexpectedly brought about significant increases in his memory, according to Smith.
Smith, who also is director of the Division of Geriatric Psychiatry and Neuropsychiatry at Johns Hopkins Bayview Medical Center, is an authority on mapping the brain’s glucose metabolism in aging and psychiatric disease. It was her earlier analysis of Alzheimer’s patients’ PET scans that revealed their pattern of lowered brain metabolism. She determined that specific parts of the temporal and parietal cerebral cortex — memory network areas of the brain where Alzheimer’s earliest pathology surfaces— became increasingly sluggish with time.
The new study was supported by grants from the Neurosurgical Research and Education Foundation, the Dana Foundation and the Krembil Neuroscience Discovery Fund.