Indication of surgical therapy for Parkinson's disease

We review the current status of surgical treatment of Parkinson's disease (PD). The advantages of deep brain stimulation (DBS) over ablative surgery include reversibility and controllability of stimulation. In addition, DBS carries a smaller risk of side effects, especially when employed bilaterally. DBS of the thalamus is useful to control tremor which is unresponsive to medication. DBS of the globus pallidus internus (GPi) or the subthalamic nucleus (STN) is useful to control wearing off of motor symptoms which is difficult to manage with medication alone. DBS of STN and GPi improves motor function mainly during the off-period. DBS of STN attenuates levodopa-induced dyskinesia through reduction of dopa requirement, whereas DBS of GPi attenuates dopa-induced dyskinesia directly. DBS of STN is also useful to control symptoms of PD in patients who are intolerant to dopa. However, DBS of either STN or GPi cannot reverse advanced symptoms of PD, which are unresponsive to dopa.