No effect of a levodopa single dose on motor performance and motor excitability in chronic stroke. A double-blind placebo-controlled cross-over pilot study

Drugs that modulate neuronal transmission can influence motor recovery after stroke. Here, we tested if a single dose of levodopa could improve motor functions and change motor excitability in a group of chronic stroke patients. Ten patients > 6 months after their stroke participated in a placebo-controlled double-blind trial. On two different occasions, they received either 100 mg levodopa or placebo in a randomized order. After drug intake, they participated in one hour of physiotherapy aimed at an improvement of dexterity. Motor functions were tested by application of the Nine-Hole-Peg Test, a dynamometer measuring grip strength and the Action Research Arm Test. In addition, transcranial magnetic stimulation (TMS) was applied to study intracortical excitability, stimulus response curves and silent periods. TMS studies and motor function measurements were performed before drug intake, 45 minutes after drug ingestion and after the physiotherapy. Compared to placebo, levodopa neither improved motor functions nor changed motor excitability as tested by TMS. These findings suggests that a single levodopa dose is not sufficient to improve motor function in chronic stroke. However, it cannot be excluded that the lack of a beneficial effect is related to the small study sample.