Functional changes in spinal circuitry in essential tremor revealed with analysis of intramuscle synergies

This is the first study exploring the recently described phenomenon of intramuscle synergies in neurological patients. Patients with essential tremor showed reduced indices of such synergies during cyclical finger force production compared with patients with Parkinson's disease and two groups of controls. This reduction reflected the reduced flexibility in the recruitment of motor unit groups. Studies of intramuscle synergies are promising to provide a sensitive biomarker of spinal circuitry.