Levodopa Is a Double-Edged Sword for Balance and Gait in People With Parkinson's Disease.

BACKGROUND The effects of levodopa on balance and gait function in people with Parkinson's disease (PD) is controversial. This study compared the relative responsiveness to l-dopa on six domains of balance and gait: postural sway in stance; gait pace; dynamic stability; gait initiation; arm swing; and turning in people with mild and severe PD, with and without dyskinesia. METHODS We studied 104 subjects with idiopathic PD (H & Y II [n = 52] and III-IV [n = 52]) and 64 age-matched controls. Subjects performed a mobility task in the practical off state and on l-dopa: standing quietly for 30 seconds, initiating gait, walking 7 meters, and turning 180 degrees. Thirty-four measures of mobility were computed from inertial sensors. Standardized response means were used to determine relative responsiveness to l-dopa. RESULTS The largest improvements with l-dopa were found for arm swing and pace-related gait measures. Gait dynamic stability was unaffected by PD and not responsive to l-dopa. l-dopa reduced turning duration, but only in subjects with severe PD. In contrast to gait, postural sway in quiet standing increased with l-dopa, especially in the more severely affected subjects. The increase in postural sway, as well as decrease in turning duration and exaggerated arm swing with l-dopa was observed only for subjects with dyskinesia at the time of testing. CONCLUSIONS The observed spectrum of l-dopa responsiveness in balance and gait measures suggests that multiple neural circuits control balance and gait. Many of the negative effects of l-dopa may be directly or indirectly caused by dyskinesia.