To Drive or Not to Drive

August 30, 2010
Steven Zuckerman, MD

Neurologists are called upon to assess people who may not possess the necessary skills to safely operate a motor vehicle for various reasons.

In the last post, I discussed the recent AAN guidelines regarding patients with dementia and their driving privileges. As neurologists, however, we are called upon to assess people who may not possess the necessary skills to safely operate a motor vehicle for other reasons. Besides the cognitive sphere discussed in the last post, there are also visual abilities that are critical to safe driving. In addition, sensorimotor functions must be sufficient for driving control. Finally, episodic alterations in levels of consciousness—seen in conditions like epilepsy, syncope, or sleep apnea—also fall under the neurologist’s purview.

In regards to epilepsy, each state has its own set of regulations. Six states place an obligation on the physician to report patients with epilepsy, whereas the others don’t. For individual state regulations, please refer to Chapter 8 of the AMA Guidelines. Keep in mind that commercial motor vehicle operators have an entirely different set of standards/regulations. For example, patients with a history of epilepsy cannot qualify for a license unless they are seizure free off of medications for 10 years. After a solitary unprovoked seizure, the patient must go 5 years off of medication in order to qualify to reapply for a license.

For other types of conditions, the AMA has established an ADReS Score (Assessing Driving Related Skills). This is a battery of tests that may be performed in the office in 10-15 minutes to screen for inadequacies in any of the three essential skill sets: visual, cognitive, and sensorimotor. A score sheet is available for download as an Appendix from Chapter 3 of the above AMA website.

  • Vision is screened by means of two assessments:
  • Visual acuity with a Snellen Chart at 20 feet to ensure >20/40 Vision
  • Visual fields determination
  • Cognitive screening is done by means of the Trail-maker B test. This is a test in which the patient is instructed to connect circles. There are numbers from 1 to 13 and letters from A to L, and the task involves alternating from the number to the next letter (ie, 1 to A, then to 2 and then B). The examiner corrects any mistakes, which automatically increases the time required to finish the task. There is apparently good data correlating performance on this test with recent at-fault crashes. Why this test was not evaluated in the recent guidelines is unclear, especially since one of the authors acknowledged that utilizing this test was a reasonable approach.
  • Motor abilities are screened by two types of evaluation:
  • A range of motion determination
  • Motor group testing for strength on the classic 0 to 5 scale
  • A timed twenty-foot walk. A line is indicated at ten feet and the patient instructed to walk to that line and return as rapidly as is comfortable. Greater than 9 seconds is abnormal and indicates driving risk.

Of course, successfully passing all of the above tests does not guarantee safe driving ability. These are all surrogate testing for the necessary driving skills, but should not replace an on-road driving test if there is any doubt about an individual’s safety behind a wheel. I would suspect that given the sophistication of simulated driving games, there may be other testing developed that would more accurately predict who is at risk for causing accidents. Until the studies are done that can validate that type of technology, the ADReS is a practical and sensitive battery of tests that should be employed in the neurologists office to assist in making a rational decision regarding driving privileges.