Supraspinal inputs reduce corticomotor excitability during passive movement: evidence from a pure sensory stroke.

Overview

Corticomotor excitability is reduced during rhythmic passive movement compared to rest, but it is not known whether the mechanism is purely segmental or includes a supraspinal pathway. To determine how interruption of sensory projections at a supraspinal level affects corticomotor excitability during passive movement, we measured the amplitude of motor evoked potential (MEP) during 1 Hz cyclic index finger movements in a patient with a brainstem and thalamus lesion that resulted in a pure sensory stroke. Measurements of MEP amplitude and proprioception were made 14 and 64 days post-stroke. In the first study, when subjective position sense was reduced for the index finger, MEP amplitude was significantly increased during passive movement compared to rest (4.6+/-0.2 SEM mV vs. 4.0+/-0.2 mV; p=0.0281). However in the second study, when position sense had returned to normal, MEP amplitude was significantly reduced during movement compared to rest (6.2+/-0.3 mV vs. 6.6+/-0.1 mV; p=0.0224). These observations provide evidence that supraspinal sensory pathways are involved in reducing corticomotor excitability during rhythmic passive movement.