Brain scans have revealed that the first gene-based therapy for Parkinson's disease was effective.
Gene therapy has never before been used to treat a degenerative brain disease in humans and the success represents an important landmark.
For the study scientists at the New York University School of Medicine injected the brains of Parkinson's patients with a harmless virus which was genetically modified.
The virus carried a human gene which dampens down the nerve cells that become overactive in Parkinson's patients which as a result interferes with movement control.
Position emission tomography (PET) scans were carried out before the surgery and repeated six months later and then again one year after the surgery.
The PET scans revealed how the activity of different brain circuits changed before and after treatment and confirmed the treatment worked by highlighting brain circuits involved in movement that had recovered; a significant improvement was also noted in the patients.
The brain scans were part of the treatment in the on-going trial which involved eleven men and one woman.
The patients received the injections directly into part of the brain most affected by the disease and the scans later showed that some brain circuits that act abnormally in Parkinson's patients were working healthily again.
The genes were delivered to only one side of the brain to reduce risk and to better assess the treatment.
Signs of recovery were seen one month after treatment, and three to six months later all showed on average a 30% improvement in their movement; one patient in particular astounded the doctors, after tests showed his movement had improved 65%.
Dr. David Eidelberg, who led the study says the scans show that the treatment corrects abnormal activity in the brain, which in itself shows the therapy works.
Dr. Eidelberg says before the patients' brains were scanned it was unclear whether their recovery could be explained by the placebo effect, or even by the surgery to enable doctors to inject the gene-based drug into their brains.
However a detailed examination of the scans showed very specific changes in the patients' brains that could only be explained by the therapy, says Eidelberg.