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 53pc 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 30pc improvement in various activities of daily life, including speech, writing, dressing and walking.
Side effects from drug treatment, including uncontrollable movements, were reduced by 61pc.
The findings are published in the 'New England Journal of Medicine'.
Earlystim investigator Professor Gunther Deuschl, from Christian-Albrechts University in 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: "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.