A small safety trial suggests a pacemaker-like device implanted into the brains of Alzheimer's patients may stimulate beneficial brain activity in some.
"What we can say is that the changes in brain activity are encouraging, but before we can make any sort of comments about the potential of the treatment we really have to study it in more individuals," said Dr Gwenn Smith, the study's lead author, from Johns Hopkins University School of Medicine in Baltimore.
The implant, which delivers continuous electrical impulses into the brain, is already commonly used in patients with Parkinson's disease and tremors to help control their movements.
Research is promising
Although the new research is only in its beginning stages, it's a promising avenue to explore since available Alzheimer's treatments "aren't that great," said Dr Bryan Klassen, a neurologist at the Mayo Clinic in Rochester, Minnesota, who was not involved in the study.
Dr Smith, who was part of a team that did the initial research while at the University of Toronto, said they are just starting to look into what this could mean for Alzheimer's patients.
The researchers, who published their findings in the Archives of Neurology, came to the idea of testing the device in Alzheimer's patients after using a study of brain pathways involved in appetite showed that memory improvement was an unexpected side effect of the brain stimulation.
How the study was done
In the new study, Dr Smith and her colleagues looked at the brain activity of five patients, all around 63 years old, who were diagnosed with mild Alzheimer's and had been on medication to promote brain function for at least six months.
Each patient had the device implanted near the fornix, a region of the brain thought to be important in storing memories, and the stimulator was turned on two weeks later. The researchers kept the device settings and the patients' medications constant for 12 months.
PET scanning – an indirect measure of brain cell activity that tracks the cells' demand for blood flow -- was performed on each patient at the one-, six- and twelve-month mark.
The researchers were looking for changes along a "circuit" of brain regions where activity levels are known to subside as Alzheimer's progresses. That dampening of chatter among brain cells along the circuit is thought to underlie several Alzheimer's symptoms.
Overall, they saw an increase in brain activity in all five Alzheimer's patients with implants.
"The regions are not working together in concert as you would observe in normal individuals... but we were seeing an increase in brain activity. You wouldn't see that in people with normal Alzheimer's," said Dr Smith.
The participants who started out with higher levels of brain activity, and those with the highest levels at the end of the study, tended to have the best results on tests of cognitive function and quality of life. But no one displayed dramatic improvements in those categories.
Cost of the device
As a group, the participants' cognitive ability declined over time from about 19 – on a scale of zero to 70, with higher scores representing worse performance – to 24 at the end of twelve months. One patient did improve his test score by about four points, but that result could have been due to chance.
Quality of life – measured on a scale of 13 to 52 points, with higher numbers representing worse quality – barely changed. Scores for the group were 36 at the beginning of the study and 35 after 12 months.
"Basically, as a group, the patients experienced the decline you'd expect to see over time, but the decline was slightly less than expected," Dr Smith said.
According to Dr Klassen, the most interesting finding is the evidence of increased brain-cell activity. "What this added is they looked at this change in the blood flow, and those who had better blood flow seemed to do better in decline," he said.
Since the study was a very small phase I trial, and the implant is not approved to treat Alzheimer's, it's important to temper the findings because of the limited amount of data, Dr Smith said.
"I think that unless we evaluate the procedure in more individuals, it's really hard to make any claims about what the potential is," she said. Any benefits of a potential treatment based on deep brain stimulation would also have to be weighed against its risks and costs.
Dr Klassen said that the price for the device and the surgery in patients with Parkinson's disease can range from $60,000 to $100,000. But, he said, it's become a reasonably safe procedure and most patients are sent home the next day.
(Reuters Health, Andrew M. Seaman, May 2012)
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