Focused bursts of sound far beyond the range of human hearing can significantly ease the tremors that make life difficult for sufferers of Parkinson's Disease. The finding is part of a wave of experiments using ultrasound as a way to treat brain conditions without the dangers of surgery.
Parkinson's disease comes in contrasting forms, with some patients tending to become rigid and unable to move, while others move too much, with tremors shaking their hands to the point where even eating can be a fraught procedure.
Deep brain stimulation has proven successful for many people with tremor-dominant Parkinson's disease (TDPD), although the underlying reasons for its effectiveness remain unclear. Unfortunately, however, the risks involved in having electrodes planted in the brain are considerable, preventing many people who might benefit from undergoing the operation.
Dr Jeff Elias of the University of Virginia exposed 20 people with TDPD to 710 kiloHertz ultrasound waves focused on the thalamus, one of several parts of the brain thought responsible for the tremors. Another seven, selected randomly, were given a placebo – put into the same equipment and unaware the ultrasound was not working when it was supposedly being applied to them.
The results were striking, with patients experiencing a 62 percent improvement three months after the treatment on a scale that measures a variety of hand tremors. Those who received the fake treatment also experienced an improvement, demonstrating yet again the power of the placebo effect, but their gain was only 22 percent. The control group was offered the chance to take up the real treatment after the trial was over.
In JAMA Neurology, Elias reports some side effects. However, these were either rare – for example temporary weakness experienced by two participants – or relatively minor, primarily numbness in certain parts of the body.
The findings are particularly impressive because all those who took part in the study had previously tried other treatments without success.
The ultrasound is focused so that waves combine at a particular point in the brain creating a hotspot. This heat can be used like a scalpel, cutting out damaged tissue or altering misfiring brain circuits. Unlike traditional surgery, however, there is no need to cut through surrounding tissue to get to the relevant region, and consequently no danger of infection. The process is monitored with magnetic resonance imaging to make sure damage is not done to non-target areas of the brain. Patients were assessed both three months and a year after treatment.
Focused ultrasound was first used to treat neuropathic pain in 2009, and trials of its use for tremors caused by conditions other than Parkinson's have been so successful that it has won FDA approval.