Neurosurgical Approaches to Levodopa-Induced Dyskinesia

Levodopa has long been the standard of care for Parkinson disease (PD); however, the eventual onset of motor fluctuations and levodopa-induced dyskinesia (LID) complicates its utility in advanced PD. Current neurosurgical interventions remain some of the best options for LID. Deep brain stimulation (DBS) is currently the procedure of choice for patients with advanced PD, patients refractory to medical management, and patients with motor complications from levodopa therapy. Significant progress has been achieved in recent years, however, as newer techniques are making their way through preclinical and clinical studies. Use of interventional magnetic resonance imaging (iMRI) and a skull-mounted aiming device to guide electrode placement has improved accuracy in recent DBS studies. Adaptive "closed-loop" DBS represents another exciting advancement in the field, in which real-time feedback allows dynamic modulation of the stimulation delivered to the basal ganglia. Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel approach to creating precise lesioning in the brain that has shown promising results in preliminary studies for various movement disorders, including dyskinesias, and may transform the neuroablation field. Transcranial magnetic stimulation, which can induce local and distant effects in cortical and subcortical areas, has shown efficacy in managing certain PD and LID symptoms in early studies. Finally, direct stimulation of the motor cortex and the cerebellum has shown therapeutic effects in PD and LID patients in certain studies. Taken together, many of these new techniques have shown great promise in early studies and may eventually be preferred treatment options for LID patients.