Levodopa unresponsive symptoms in Parkinson disease.

Levodopa has been the mainstay of symptomatic therapy for Parkinson Disease (PD) for 40 years providing benefit to virtually all patients. Levodopa therapy results in improved activities of daily living, enhanced quality of life, and improved mortality. However, the long-term use of levodopa is associated with the development of motor fluctuations and dyskinesia. In addition, levodopa therapy has further limitations. It has little or no effect on certain motor features (e.g. gait and balance dysfunction) and a non-motor symptom complex (autonomic dysfunction, pain syndromes, sleep disorders, mood disturbances, dementia). Further, multiple case reports illustrate the potential of levodopa and other dopaminergic agents to cause or reveal a series of impulse control disorders. This review highlights the levodopa unresponsive symptoms in PD.