Youth with essential tremor differ from age-matched controls in multiple aspects of visually-guided reaching...

Essential tremor (ET) likely includes deficits outside tremor, though this is under-examined in youth. We tested the hypothesis that reaching movements in youth with ET are characterized by greater incoordination.

Fifteen youth with ET (ages 11 to 17) recruited from the Calgary Tourette and Pediatric Movement Disorders Clinic completed a visually-guided reaching task using the Kinarm Exoskeleton Lab. Performance in several kinematic parameters was compared with age-matched controls.

Youth with ET differed from controls in multiple parameters. In the dominant arm, the initial portion of reaching movements was slower and smaller-amplitude, with longer reaction time and greater posture speed at movement end when the hand should be at rest. In the non-dominant arm, those with ET differed from controls in a larger number of parameters. All but three with ET were impaired in at least one task parameter, scoring outside age-predicted norms.

Our study supports the notion of ET as a disorder with abnormalities beyond tremor, and that motoric abnormalities are demonstrable in youth with ET.

This is the first study showing youth with ET differ from age-matched controls in multiple aspects of reaching movements, including initial trajectory control, movement smoothness, overall trajectory, and endpoint control.