Alzheimer's damage reversed by deep brain stimulation

BRAIN shrinkage in people with Alzheimer's disease can be reversed in some cases - by jolting the degenerating tissue with electrical impulses. Moreover, doing so reduces the cognitive decline associated with the disease.

"In Alzheimer's disease it is known that the brain shrinks, particularly the hippocampus," says Andres Lozano at Toronto Western Hospital in Ontario, Canada. What's more, brain scans show that the temporal lobe, which contains the hippocampus, and another region called the posterior cingulate use less glucose than normal, suggesting they have shut down. Both regions play an important role in memory.

To try to reverse these degenerative effects, Lozano and his team turned to deep brain stimulation - sending electrical impulses to the brain via implanted electrodes.

The group inserted electrodes into the brains of six people who had been diagnosed with Alzheimer's at least a year earlier. They placed the electrodes next to the fornix - a bundle of neurons that carries signals to and from the hippocampus - and left them there, delivering tiny pulses of electricity 130 times per second.

Follow-up tests a year later showed that the reduced use of glucose by the temporal lobe and posterior cingulate had been reversed in all six people (Annals of Neurology, DOI: 10.1002/ana.22089).

The researchers have now begun to investigate the effects on the hippocampus. At the Society for Neuroscience annual meeting in Washington DC last week they announced that while they saw hippocampal shrinking in four of the volunteers, the region grew in the remaining two participants.

"Not only did the hippocampus not shrink, it got bigger - by 5 per cent in one person and 8 per cent in the other," says Lozano. It's an "amazing" result, he adds.

Tests showed that these two individuals appeared to have better than expected cognitive function, although the other four volunteers did not.

Though Lozano is not sure exactly how the treatment works, his team's recent work in mice suggests that the electrical stimulation might drive the birth of new neurons in the brain. Deep brain stimulation in mice also triggers the production of proteins that encourage neurons to form new connections.

The researchers are now embarking on a trial involving around 50 people, but John Wesson Ashford at Stanford University, California, wonders how practical the approach will be when there are millions of people with Alzheimer's.

Lozano points out that around 90,000 people worldwide with Parkinson's disease have already received deep brain stimulation. The incidence of Alzheimer's is only five times that of Parkinson's, he says. "If it can be used in Parkinson's, it can be used in Alzheimer's."

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