For several decades surgeons have been using deep brain stimulation (DBS) to treat severe Parkinson's disease, delivering mild electric currents to parts of the brain to alleviate motor symptoms. A new study has marked a significant step forward for the technology, with researchers having upped the precision to target specific types of cells, which sees the effects of the therapy last several times as long in animal models.
Deep brain stimulation for Parkinson's involves surgically implanting tiny wires into targeted areas of the brain, delivering mild electrical impulses to the region responsible for movement. This has been approved as a treatment for tremors associated with Parkinson's since 1997, and recent studies have shown how it can boost dopamine levels and potentially slow progression of the disease. But one aspect scientists would like to improve upon with regard to motor symptoms is how long the effects last for, with recipients relying on continuous stimulation to prevent ongoing tremors.
Aiming to extend the benefits of these dramatic interventions, scientists at Carnegie Mellon University made a key discovery in this area in 2017. The researchers found they could control neurons in the inner circuitry of the basal ganglia, a brain region that stops working properly in Parkinson's sufferers, to provide long-lasting relief from involuntary movement in mouse models of the disease.
The trouble was that the scientists achieved this through optogenetics, a highly promising technology that uses light to control genetically modified cells, but one that couldn't be safely applied to humans in this scenario. The challenge therefore was to adapt this approach so that it could be safe, and replicate the effects of targeting specific neuronal circuity without leaning on optogenetics.
Through their experiments on mice, the team found that they could target specific sets of neurons in part of the basal ganglia called the globus pallidus with short bursts of electrical stimulation, to great effect. This discovery came about by studying the biology of these cells and the "inputs that drive them," allowing the scientists to find a sweet spot that brought about the desired effects.
“This is a big advance over other existing treatments,” says Aryn Gittis, lead author of the study. “In other DBS protocols, as soon as you turn the stimulation off, the symptoms come back. This seems to provide longer lasting benefits – at least four times longer than conventional DBS.”
These results were only observed in mice, but the scientists will next carry out a randomized, double blind crossover study of Parkinson's patients to explore the safety and tolerability of the DBS technique in humans. This will assess the subjects over a 12-month period, tracking improvements in their motor symptoms and the frequency of adverse events.
“By finding a way to intervene that has long-lasting effects, our hope is to greatly reduce stimulation time, therefore minimizing side effects and prolonging battery life of implants," says Gittis.
The research was published in the journal Science.
Source: Carnegie Mellon University via EurekAlert