A treatment that involves inserting electrodes into the brain can improve Parkinson's symptoms even at early stages of the disease, research has shown.
Currently, Deep Brain Stimulation (DBS) is reserved for patients with advanced Parkinson's disease who can no longer be treated with medication alone.
The Earlystim study showed that DBS produced a 53% improvement in motor skills over a period of two years. In comparison, no change was seen in patients receiving the best drug treatment.
Patients given DBS also saw a 30% improvement in various activities of daily life, including speech, writing, dressing and walking.
Side effects from drug treatment, including uncontrollable movements, were reduced by 61%.
The findings were published yesterday in the New England Journal of Medicine.
Earlystim investigator Professor Gunther Deuschl, from Christian-Albrechts University in Kiel, Germany, said: "These results signal a shift in the way patients with Parkinson's disease can be treated, and prove that deep brain stimulation therapy can improve patients' quality of life even in the earlier stages of Parkinson's disease."
The trial included 251 patients with Parkinson's disease at 17 centres in Germany and France.
Dr Kieran Breen, from the charity Parkinson's UK, said: "This new study is the first compelling evidence to demonstrate that deep brain stimulation - brain surgery traditionally used to treat the later stages of Parkinson's - may be beneficial for some people in the earlier stages of the condition.
"In this study of 251 people, the researchers found that that those who had had deep brain stimulation reported a better quality of life two years later, than those who had chosen not to have the surgery.
"Studies like these are vital to help doctors identify those most likely to benefit, and to make sure people with Parkinson's at whatever stage have access to this important treatment.
"However, it is important to remember that not all people with Parkinson's are suitable for this surgery, and though the results can be dramatic - with a reduction in tremor and stiffness - not everyone who has it will find their lives transformed."