information:classification, structural:reformatting
Surgery

Treating motor symptoms with surgery was once a common practice but the discovery of levodopa has decreased the amount of procedures. Studies have led to great improvements in surgical techniques, so surgery can be used in people with advanced PD for whom drug therapy is no longer sufficient. Surgery for PD can be divided in two main groups – lesional and deep brain stimulation (DBS). Target areas for DBS or lesions include the thalamus, globus pallidus, or subthalamic nucleus. DBS involves the implantation of a medical device called a neurostimulator, which sends electrical impulses to specific parts of the brain. DBS is recommended for people who have PD with motor fluctuations and tremor inadequately controlled by medication, or to those who are intolerant to medication lacking severe neuropsychiatric problems. Other less common surgical therapies involve intentional formation of lesions to suppress overactivity of specific subcortical areas. For example, pallidotomy involves surgical destruction of the globus pallidus to control dyskinesia.

Four areas of the brain have been treated with neural stimulators in PD. These are the globus pallidus interna, thalamus, subthalamic nucleus, and pedunculopontine nucleus. DBS of the globus pallidus interna improves motor function, while DBS of the thalamic DBS improves tremor, but has little impact on bradykinesia or rigidity. DBS of the subthalamic nucleus is usually avoided if a history of depression or neurocognitive impairment is present. DBS of the subthalamic nucleus is associated with a reduction in medication. Pedunculopontine nucleus DBS remains experimental at present. Generally, DBS is associated with 30–60% improvement in motor score evaluations.