Quantifying loss of motor skills after cerebellar stroke

Abstract

A cerebellar stroke causes motor deficits and may complicate daily activities of patients. Their movements become uncoordinated with errors in speed and accuracy. To quantify the level of impairment, this paper proposes a preview tracking task. Such a task assesses and quantifies eye-hand coordination skills.
A preview experiment on a touch-screen has been conducted with four cerebellar patients, four age-matched healthy control subjects, and a group of 26 young adults. Age-matched control subjects and young adults performed eight runs of the preview task, with the dominant hand only. Patients performed eight runs with each hand to make a distinction between the hand affected by the lesion and the unaffected hand. During the experiment, both eye- and hand movements were recorded. Results were obtained with system identification techniques. A model of the human controller in preview tasks was fitted to the estimated frequency response of the subject. The resulting control parameters revealed the tracking behaviour of the subjects. Patients show significantly higher visual time delays, neuromuscular damping ratios and lead time constants than age-matched control subjects. Consequently, patients engage in a more cautious control strategy than age-matched control subjects.
Overall, the proposed task is found to be capable of detecting visuo-motor impairment in cerebellar patients. It could be used to quantify impairment as a result of neurological disorders, and monitor improvement during the revalidation phase and afterwards.