“On” Freezing in Parkinson Disease

These researchers studied a Parkinson disease (PD) clinical phenomenon that has been referred to as “on” freezing of gait. Simply put, when patients with PD take dopamine-replacement therapy, they usually report feeling “on.” During this state, they also commonly report that many of their PD symptoms improve (e.g., tremor, stiffness, slowness, and in some cases, gait). Clinicians have observed that, in rare cases, the gait actually worsens after medication administration. To better describe this phenomenon and to develop a systematic method to diagnose it, the authors studied four patients with PD (of 6–20 years' duration) in each of three medication states: off medication for 12 hours, during their best on-medication state, and during the …