Advanced Huntington’s Patients Have Marked Difficulties in Driving, Study Shows

Patients at advanced stages of Huntington’s disease have marked difficulties in controlling vehicles in a driving simulator compared to patients who are at a pre-symptomatic stage or healthy subjects, a study shows.

The study’s authors think such driving simulators could be useful screening tools to aid clinicians in their referral for an official on-road driving test.

The study, “Predictors of simulated driving performance in Huntington’s disease,” was published in Parkinsonism and Related Disorders.

Huntington’s disease is a genetic neurodegenerative disorder characterized by the progressive loss of motor, psychiatric and cognitive abilities. Huntington’s has several stages, ranging from an initial  phase in which patients experience no symptoms to an advanced stage in which patients require full support from caregivers to perform daily activities.

As disease progresses and patients become less independent, they often face questions: “Am I still able to drive by myself? Must I quit driving?” For most patients, the decision is difficult because it has a direct impact on their independence and ability to engage in social activities.

“We are of the opinion that it is important to determine who is still able to drive safely instead of focusing on who is no longer fit to drive, since this might prolong the time a patient can be independent,” researchers said.

So far, only two studies have assessed Huntington’s patients’ driving abilities using a driving simulator. Both showed that Huntington’s patients reacted more slowly and committed more errors when driving compared to healthy individuals.

However, it remained unclear whether the outcomes of standard clinical assessment tests, such as those for cognitive, motor and psychiatric symptoms, correlated with patients’ performance in the driving simulator and whether patients still at a pre-symptomatic stage of the disease already presented with driving issues.

To address this gap, researchers preformed an observational and cross-sectional study recruiting 58 patients with Huntington’s disease — 28 in a pre-symptomatic phase and 30 at a more advanced stage of the disease — along with 29 healthy control subjects.

All participants underwent clinical assessment to determine the extent of their neuropsychological, motor, and psychiatric symptoms and were asked to drive a car on a motorway scenario in a driving simulator to evaluate their driving performance.

Patients at more advanced stages of Huntington’s disease performed poorly on clinical assessments, drove more slowly and had more difficulty controlling vehicles in the driving simulator, compared with those at earlier stages of the disease and healthy control subjects.

There were no significant differences in driving performance between pre-symptomatic Huntington’s patients and controls.

Unlike psychiatric symptoms, motor and cognitive symptoms including postural sway (lack of body balance) and slower information processing were correlated with patients’ performance in the simulator.

“[O]ur study revealed that increased postural sway and slower speed of processing are predictive of driving simulator performance in manifest HD [Huntington’s disease]. This highlights the importance of discussing driving and cognitive functioning for those treating patients with HD. Worse performances on clinical screening tasks might assist clinicians in their referral for an official on-road driving test,” researchers said.