Objectives: Huntington’s disease (HD) is a genetic, neurodegenerative disease characterized by motor and behavioral symptoms and decline in cognitive abilities relevant to everyday function. Although scales of gross functional status are available, demonstrating the functional benefits of an intervention in HD remains challenging due to lack of standardized and sensitive measures of functional capacity. In recognition of this gap, a critical review was undertaken to summarize literature addressing the impact of HD on driving (as measured by simulator measures) and the relationship between clinical outcomes assessments (COAs) and driving simulator measures in an HD population.

Methods: A targeted literature review identified publications, including driving simulator and cognitive function assessments in HD. Simulated driving outcomes were grouped into categories: accidents; attention/reaction; distance control; general errors; infractions; lane position; speed. Standardized mean differences (Hedge’s g method) were generated to evaluate differences in measures between HD and community control samples. Relationships between driving measures and COAs were explored using Pearson correlation.

Results: Four publications were identified. Driving outcomes worse in HD than controls included higher frequency of accidents, tickets, errors, and some reaction time measures. Pooled estimates of effect size were not calculated as most measures were only in a single study and studies reported on multiple measures. The strength of correlations between COAs (cognitive tests, UHDRS) and driving measures ranged from low to high, and varied across driving measure categories: attention/reaction time (0.48 to 0.85), lane position (0.04 to 0.64), driving speed (-0.35 to 0.52) and across COA measures. The Trail Making Test, commonly used in clinical evaluation of fitness to drive, was moderately correlated with speed (0.43) and lane position (0.49).

Conclusions: Many measures are used to assess the impact of HD on driving performance. Simulated driving performance shows promise as a potential functional outcome measure for therapeutic development in HD.