Surgical Modification of Motor Circuitry

The only surgical methods approved for treatment of PD involve using lesion therapy (Vitek et al., 2003) or electrical stimulation techniques (deep brain stimulation (Deutchl et al., 2006)), both of which act to ameliorate the pathological neural activity that occurs in PD. This aberrant activity arises from the disruption of the normal balance of excitatory and inhibitory regulation in the basal ganglia after the loss of nigrostriatal dopaminergic neurons. These surgical therapies are, in general, effective against the same types of motor symptoms that can be treated with pharmaceutical dopamine replacement therapies.

Lesion therapy, i.e., thalamotomy and pallidotomy, represent some of the earliest attempts to counteract the disruption of basal ganglia circuitry in PD. These procedures show efficacy in treating PD motor symptoms.

Image from NINDS, NIHDeep brain stimulation (DBS) can be effective at treating a number of motor symptoms of Parkinson's disease, and has the great advantage over lesion techniques of being adjustable and essentially reversible. DBS involves placement of stimulating electrodes in specific nuclei of the basal ganglia to reset the motor circuit affected in PD. Target areas for DBS include the internal segment of the globus pallidus and the subthalamic nucleus (Stefani et al., 2007). A number of PD symptoms, such as postural instability and gait disturbances, remain untreated by DBS. Recent studies have investigated whether DBS to the pedunculopontine nucleus (PPN) may be effective as a treatment for postural instability and gait disturbances. DBS to the thalamus has also been used to treat tremor. At this time, the mechanism through which DBS works remains unknown.