In Parkinson’s disease (PD), levodopa (LD) initially controls the symptoms of most patients, but after a few years of treatment motor complications develop. Dopamine agonists (DAs) or monoamine oxidase type B inhibitors (MAOBIs) have been used, either alone or with reduced doses of LD, in an attempt to delay the onset of motor fluctuations.
Once motor complications develop, DAs or MAOBIs may be introduced if not previously used, as may catechol-O-methyltransferase inhibitors (COMTIs), but in many patients these eventually fail to maintain adequate control of symptoms. At this point (or potentially earlier), surgical intervention may be considered. Surgery may be performed at three sites (thalamus, globus pallidum or subthalamic nucleus) using two techniques (radio frequency lesioning or electrical stimulation). There is very little reliable evidence available as to the optimal site, technique and timing of surgery. Few randomised trials have addressed these questions, and those that have been performed have been small. Most published reports relate to small non-randomised series, which can not provide reliable evidence because of the potential selection biases involved. There is, therefore, an urgent need for large randomised trials of surgery for PD to be undertaken.