Sure I can Drive, Now Where did I Put the Car

This inagural post is part 1 of a 2 part series.

The practice guideline Evaluation and Management of Driving Risk in Dementiawas presented at the AAN Meetings in Toronto in April and published in the April 20 issue of Neurology. This was a comprehensive review of the literature, filtering information from 6,000 abstracts and more than 500 articles (of which thirty articles were actually utilized to formulate the final recommendations). If you missed the presentation or the published article, not to worry; I am here to fill you in on everything you missed. In a word, nothing.

As neurologists, we are called upon to decide whether someone should have their driving privileges revoked because of some cognitive deficits. However, studies have shown that in patients with mild dementia, there is a surprisingly high percentage who can pass an on-road driving test and are, in fact, safe drivers. This may be as high as 75%. We would certainly not want to remove driving rights from someone who can safely operate a motor vehicle, particularly given the dire social and personal consequences to that individual. So, a systematic literature review with high-quality data would help in making evidence-based decisions, right? Unfortunately, this information apparently does not exist in the literature, and the resultant “guidelines” offer only a vague approximation of driving risk. In fact, it is not a guideline at all given the inconclusive nature of the recommendations provided.

Here are the conclusions of this “practice parameter:”

• The Mini Mental Status Examination (MMSE), the standard clinical tool for determining severity of dementia, was not very sensitive in distinguishing a safe from an unsafe driver. MMSE of less than 24 is likely of increased driving risk
• The Clinical Dementia Rating (CDR) score, a test not typically performed outside of research settings, was more informative. This scale includes 0, 0.5, 1 (mild), 2 (moderate), and 3 (severe) for final outcomes. At levels 2 and 3, driving should be stopped. At levels 0.5 and 1, there is some increased risk for unsafe driving, but other factors should be taken into account before deciding to pull a license. These include: Caregiver report of unsafe driving History of traffic violations or accidents Self-limiting of driving Aggressive or impulsive personality traits

The Neurologyarticle published the details of the questions to ask in the CDR, but you would have to go to a separate source in order to determine the CDR. If this is 0.5 or 1, you would add up the additional risk factors mentioned above to make an estimate of driving risk. The conclusions are not sufficiently accurate to make any definitive driving recommendations. In fact, when asked about this lack of practical application of this information, an author responded

Dr. Gronseth:” … it’s important to realize that there is a lot of opinion involved when the evidence is this weak, so you have to use your judgment. Dr. Iverson gave a nice example of this when he explicitly said that, in his opinion, the Trail Making Test is valuable. That’s certainly a reasonable opinion, and one that a lot of people share. However, not everyone does share that opinion, and you might decide to rely on something else, because we don’t know what’s better, and, as Dr. Iverson said, that is the art of medicine. In this specific case, the best you can do is get a gestalt based on all the things you know are useful and then add to that the things you believe are useful. Then you can make a decision or recommendation to the patient and the family.”

Really? After publishing a “guideline” we resort to “reasonable opinion,” “gestalt,” and “art of medicine”? And I was under the impression that evidence-based guidelines were supposed to provide a more rational basis for making clinical decisions. My bad.

Look for part 2 of this blog, coming the week of August 30, 2010.

For the past 2 years, Dr. Zuckerman has served on the Louisiana Medical Advisory Board that makes the final decisions regarding driving privileges in disputed cases. His website features electronic forms to help assess all neurological conditions that may impair driving (seizures, stroke, Parkinson’s, dementia).