Graphomotor Dysfluency as a Predictor of Disease Progression in Premanifest Huntington's Disease.

Abstract

Prior studies have relied on conventional observer-based severity ratings such as the Unified Huntington's Disease Rating Scale (UHDRS) to identify early motor markers of decline in Huntington's disease (HD). The present study examined the predictive utility of graphomotor measures handwriting and drawing movements. Seventeen gene-positive premanifest HD subjects underwent comprehensive clinical, cognitive, motor, and graphomotor assessments at baseline and at follow-up intervals ranging from 9-36 months. Baseline graphomotor assessments were subjected to linear multiple regression procedures to identify factors associated with change on the comprehensive UHDRS index. Subjects were followed for an average of 21.2 months. Three multivariate regression models based on graphomotor variables derived from a complex loop task, a maximum speed circle drawing task and a combined task returned adjusted R2 coefficients of 0.76, 0.71, and 0.80 respectively accounting for a significant portion of the variability in cUHDRS change score. The best-fit model based on the combined tasks indicated that greater decline on the cUHDRS was associated with increased pen movement dysfluency and stroke-stroke variability at baseline. Performance on multiple measures of graphomotor dysfluency assessed during the premanifest or prodromal stage in at-risk HD individuals was associated with decline on a multidimensional index on HD morbidity preceding an HD diagnosis.