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Issue 91, December 2005

HD and Driving

This Article is part one of three relating to HD and driving.
Subsequent articles will appear in future issues.

HD and Driving

A Physicians View: Evaluating HD Persons for Driving
Allen J Ruben, MD

Did You Know?
by Jerome M Levey

Chorea - the random, uncontrolled movement associated with HD - is not always the major cause of driving impairment in affected individuals!

Although it can be a problem for some people, the patient’s judgement is more often the factor, which can make HD people dangerous drivers.

Just as teenagers with superb coordination tend to have higher accident rates, HD persons who have little or no chorea may have more accidents due to impaired ability to anticipate situations and make rapid traffic related decisions.

Source: Evaluating Driving Capability in HD, Allen J Ruben MD, 1994.

Deciding that the person with HD should not drive is likely to be a difficult decision for the physician, who must balance his obligation to advocate the highest level of independent functioning against his obligation for public safety, and, where there is a conflict, must allow public safety to take precedence. At the same time, physicians rarely have specific training in the assessment of driving capacity.

In addition to the more obvious physical prerequisites for driving such as adequate visual acuity and motor strength, there are a number of features of HD to which the physician should pay particular attention, since they are likely to be undermined by the brain dysfunction inherent in HD. These problems will not all occur in any one individual but if significant impairment exists, any one of them could be sufficient to render driving unsafe:

  • Alertness & Attention – Drivers must have sustained attention, vigilance, and control of distractibility.
  • Acquisition of Visual information – Drivers must not neglect peripheral visual space or be unable to reposition the eyes quickly; this function can be greatly slowed in HD.
  • Processing of Visual information – Drivers must be able to process information quickly and effectively. Motion and distance must be interpreted correctly.
  • Motor Activation – Drivers must be coordinated and effective in the control of movement, be able to suppress intrusive involuntary movements of extremities, and be able to perform several motor functions at once.
  • Motor Response – Driving reaction times must be quick and linked to effective problem-solving abilities. The situations encountered in traffic require effective responses to many simultaneous stimuli and changing environments.
  • Executive Function – Judgement in driving is vital. A driver must also have the ability to anticipate problems ahead.
  • Emotional Status – Drivers must control impulses and temperament, not take undue risks, and not allow driving to express aggression or hopelessness.
  • Denial – A small minority of persons with HD will deny having impairments even when the impairments are obvious to others. This is a very dangerous trait in a driver.

The physician can take into account the driver’s ability to compensate for an identified difficulty (driving more slowly or restricting oneself to familiar destinations in light daylight traffic, for example). Learning of many recent accidents or near misses is a warning sign, as is a decline in overall functional independence in non-driving situations. When early or minor difficulties are recognized, the physician should re-evaluate every six months.

Acknowledgement: These articles are an edited version that appeared in an 1998 issue of Gateway the newsletter of Australian Huntington’s Disease Association (NSW) Inc

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