It sounds like something from the makers of Star Trek, but researchers are seeing possibilities emerge with the use of deep brain stimulation for people who have mild Alzheimer's disease. And, in a world where medications are available but the benefits are limited, it's critical to continue to develop alternate therapies to treat and prevent Alzheimer's.
What Is Deep Brain Stimulation?
Deep Brain Stimulation (DBS) is a procedure where electrodes are placed inside the brain and programmed to give off small electrical pulses to stimulate brain activity.
DBS has been used for several years for people with Parkinson's disease with considerable success in reducing tremors and muscle contractions, as well as improving posture. It's also approved by the FDA for other medical conditions, such as depression and obsessive-compulsive disorder.
How Are Electrodes Placed in the Brain?
The short answer: brain surgery. In order for DBS to be possible, wires have to be inserted into the brain. Using local anesthesia, a neurosurgeon drills holes into the skull of the patient and expertly threads wires into different areas of the brain. (Local anesthesia, when a patient is awake but an area of the body is numbed, can be used because the brain itself cannot feel any pain.)
A pacemaker-like machine is then implanted under general anesthesia into the chest of the person where it can eventually deliver 130 miniature electrical impulses per second to the wires and, consequently, the brain. When initially implanted, the stimulator is turned off; a few days or weeks after the surgery, the stimulator is turned on and begins to deliver the electrical impulses to the brain.
In Alzheimer's disease, those wires are connected to the fornix in the brain. According to Johns Hopkins Medicine, "the fornix is a brain pathway instrumental in bringing information to the hippocampus, the portion of the brain where learning begins and memories are made, and where the earliest symptoms of Alzheimer’s appear to arise."
How Does Deep Brain Stimulation Work?
There are several theories as to why it works, but there's no conclusive answer yet. In Parkinson's, it's thought to interrupt and disrupt the faulty firing of the brain.
In fact, researchers' understanding of DBS is so limited that the possibility of utilizing it for Alzheimer's was discovered accidentally when DBS was being tested on an obese man as a way to try to control his appetite. As they were testing him with the wire placement and electrical impulses, he reported a vivid memory. When they turned off the impulses, the memory went away, and when they turned the stimulator back on, the memory returned. This led to the realization that perhaps there is a way to stimulate the brain and the memories it holds.
Is It Safe?
It appears to be fairly safe. Although the thought of brain surgery sounds very risky, experts say this procedure is actually not as invasive as it sounds. There are always risks with brain surgery; however, over 80,000 people throughout the world with Parkinson's disease have undergone DBS with minimal problems. Risks include infection, equipment malfunction, stroke, battery failure and movement of the wire.
Research on Deep Brain Stimulation and Alzheimer's Disease
In 2010, the Annals of Neurology journal published research outlining a study conducted in Canada with six people diagnosed with early Alzheimer's disease. They each had a deep brain stimulator surgically implanted in their brain and experienced 12 months of continuous electrical stimulation. Testing of their cognitive functioning at six and 12 months indicated an improvement, or a less-than-expected decline in three of the six participants.
PET scans were also used to measure the levels of cerebral glucose metabolism, a measure of the activity level of neurons in the brain. Alzheimer's patients typically display a decrease in this metabolism, but these six participants showed an increase that was maintained throughout the study.
More recently, in November 2012, the first person in the United States with early Alzheimer's underwent DBS surgery. Additionally, approximately 40 patients over the next year are scheduled to be part of this study and receive DBS through Johns Hopkins. Half of them will have their stimulators turned on after two weeks, and half of them will have it turned on after 12 months. This will be a double blind study, since neither the physicians nor the patients will know when the stimulators are activated.
While early results are exciting, the effects on these 40 patients in this next study will be telling, and allow for continued monitoring for safety and effectiveness over time.
Alzheimer Research Forum. Deep-Brain Stimulation: An Electrode for All Occasions? Accessed December 9, 2012. http://www.alzforum.org/new/detail.asp?id=2452
Annals of Neurology. 2010 Oct;68(4):521-34. A phase I trial of deep brain stimulation of memory circuits in Alzheimer's disease. Accessed December 7, 2012. http://www.ncbi.nlm.nih.gov/pubmed/20687206
Baylor College of Medicine. Department of Neurology. Parkinson Disease Center and Movement Disorders Clinic. Deep Brain Stimulation. Accessed December 7, 2012. http://www.bcm.edu/neurology/parkinsons/?pmid=14184
Brown University. What Is Deep Brain Stimulation? Accessed December 9, 2012. http://biomed.brown.edu/Courses/BI108/BI108_2008_Groups/group07/what_is_dbs.html
Johns Hopkins Medicine. Johns Hopkins Surgeons Implant First Brain ‘Pacemaker’ for Alzheimer’s Disease in United States as Part of a Clinical Trial Designed to Slow Memory Loss. Accessed December 7, 2012. http://www.hopkinsmedicine.org/news/media/releases/johns_hopkins_surgeons_implant_first_brain_pacemaker_for_alzheimers_disease_in_united_states_as_part_of_a_clinical_trial_designed_to_slow_memory_loss
Journal of Alzheimer’s Disease. Research Report. Symptomatic Treatment of Memory Decline in Alzheimer’s Disease by Deep Brain Stimulation: A Feasibility Study. Accessed December 7, 2012. http://www.ncbi.nlm.nih.gov/pubmed/23168448
University of Pittsburgh. Department of Neurological Surgery. Center for Image-Guided Neurosurgery. Deep Brain Stimulation. Accessed December 7, 2012. http://www.neurosurgery.pitt.edu/imageguided/movement/stimulation.html