Motor complications are common among patients with Parkinson disease (PD) and produce considerable disability. The emergence of motor complications is related to 2 well-characterized phenomena. First, over time the pattern of response to levodopa changes and a short-duration response (SDR) emerges.1 Second, the threshold for levodopa-induced dyskinesias decreases.1 The SDR is expressed in clinicopharmacological studies as a shortening of latency to reach the peak effect or best motor response and as an increase in the magnitude of the motor response (the difference between the scores obtained in clinical rating scales or timed tests in off and on). The SDR can be considered the basic mechanism of motor fluctuations.
Linazasoro G. Pathophysiology of Motor Complications in Parkinson DiseasePostsynaptic Mechanisms Are Crucial. Arch Neurol. 2007;64(1):137-140. doi:10.1001/archneur.64.1.137