by William B. Donovan, MD
Imagine driving down the freeway
in light traffic, exiting on a ramp
with plenty of room between you and
the car in front of you. You apply the
brakes as usual, but your car begins
to go faster. The harder you press the
brake, the more the engine roars.
You hear the antilock braking system
growl, and you barely come to a stop, striking the bumper of the vehicle
ahead of you.
This story was told by an older member
of the local peripheral neuropathy support
group where I have volunteered as a medical
consultant for several years. He went
on to tell how he had taken his car to the
dealership and asked the service manager
to test drive it. To his surprise, the brakes
checked out perfectly.
Later, he recalled having read an article
about an older driver who confused the
brake and accelerator, plowing into a crowd
of pedestrians at a street fair in 2003 in
Santa Monica’s Farmer’s Market, and the
man wondered whether his own foot pedals
might be too close together.
The driver reported that he had been
experiencing some tingling, discomfort,
and numbness in his feet. On his next visit
to the doctor, he mentioned this problem.
The examination included tandem walk,
standing balance with eyes closed and arms
extended, light touch, pinprick, vibratory
and position sense, and deep tendon reflexes.
All findings were consistent with peripheral neuropathy. He was tested for diabetes, which accounts for 40 percent of peripheral
neuropathy cases, B-12 and folate deficiency
and autoimmune disorder. All of these
tests were negative, as was the patient’s history
of infections, alcoholism and other
toxic exposure, and hereditary history. The
final diagnosis was “idiopathic,” which
accounts for 40 percent of peripheral neuropathy
cases.
Referral to a physiatrist resulted in the
prescription of a progressive exercise program,
more comfortable shoes with wide
toe boxes, modification of the brake pedal
to provide greater clearance from the accelerator,
and referral to our support group.
Our member reported that he was benefiting
from the prescribed regimen and had
not had similar difficulty stopping his car
since his accident. He attends monthly
meetings of the neuropathy support group
and regularly visits the website of The
Neuropathy Association (www.neuropathy.org).
After hearing this story, I asked how
many of the members in attendance had
experienced difficulty driving, due to their
neuropathy. Well over half acknowledged
having had such driving problems — missing
pedals, misjudging how much pressure
to exert on the pedal, as well as confusing
the gas with the brake. They had adapted to
their impairment by becoming aware of
their deficit and being more cautious and
deliberate while driving.
Following the meeting, I began investigating
this issue further. An Internet search for“older driver runs over pedestrian” revealed
over one hundred citations, including the
Farmers Market massacre. I contacted several
police officers who were familiar with similar
cases. They were aware that such older
drivers “confused” the brake with the accelerator.
What was surprising was that they all
attributed the problem to cognitive, rather
than sensory, confusion. When questioned
further, they believed it would be unlikely
for a police officer to be aware of the existence
of peripheral neuropathy. Typically,
police officers would pass off the case as
being due to senility, pull the driver’s license,
and submit it to the state licensing agency
for re-evaluation.
I contacted the official responsible for
reviewing all the traffic injury reports filed
in one of the larger states for almost 30
years. Having suffered from diabetic neuropathy
himself, he was familiar with
impairment due to peripheral neuropathy.
In reviewing tens of thousands of cases, he
could recall not one report mentioning this
possible cause.
A review of the literature revealed an
enormous knowledge gap. In a study of disease
awareness, ignorance of this condition
was well-documented. Only 7 percent of
adults knew about neuropathy. This lack of
knowledge comes despite an estimate that
8 to 9 percent of Medicare recipients carry
neuropathy as either a primary or secondary
diagnosis — about 20 million people
(The Neuropathy Association, 1999).
In a survey of state driver licensing agencies,
only three out of 50 mention sensory
impairment, other than vision, as a source of
impairment (Poser, 1993). Only one article
investigated the relationship between neuropathy
and accident risk. This populationbased
case-control study found neuropathy
twice as frequently in the crash group as the
control group (McGwin, 1999).
Considering the increasing number of
aging drivers and their higher risk of accidents
per miles driven, the assessment of
driving ability is becoming more important.
Physicians needing help with the evaluation
and remediation of driver impairment have
several important sources of help.
Probably the most comprehensive reference
for physicians is the Physicians
Guide to Assessing Older Drivers, available
at www.ama-assn.org/ama/pub/category/10791.html. Help in locating occupational
therapists certified as driver rehabilitation
specialists can be found at
www.aded.net. Additional general assistance
can be found by searching the
Internet for “driver rehabilitation” by the
nearest city. Another source of help is the
state Medical Advisory boards, whose
function is to weigh medical evidence on
impairment regarding licensing.
As is usually the case, it will be the physician’s
awareness of the myriad causes of
impairment — including peripheral neuropathy— that will determine the diagnosis
and management of the driver-patient,
and the safety of our roads, for all of us.
William B. Donovan, MD is a board-certified
psychiatrist retired from the practice of pain
management. He has a degree in public health
and is engaged in the investigation of driver
safety. He is interested in hearing about cases
of older driver impairment due to peripheral
neuropathy. An annotated bibliography is available
on request at neuropathy@sbcglobal.net.
