Physicians have several examinations to help determine if a patient has developed a lack of voluntary muscular control, called ataxia. One way to determine this is called the tandem gait, which involves the patient slowly walking in a straight line, touching the heel of one foot to the toes of the other along the way. Used in concert with a variety of other movement-related tests, a variation of this walk is also a common part of the police officer's field sobriety test.
Ataxia does more than just affect the body's ability to walk in a concerted fashion. It can also hinder a person's ability to perform many voluntary movements, from eating and talking to writing and bathing. It could have many causes, including damage to the cerebellum as in a tumor or stroke, deteriorating diseases like multiple sclerosis, and developmental disorders like cerebral palsy, congenital conditions and alcoholism.
Several tests like the tandem gait are used to gauge whether a patient has ataxia, at which point radiological examinations might ensure to confirm the diagnosis. A "station test" is performed with the patient's feet spaced wider apart than normal, and then gauging whether a patient remains stable, with and without the eyes closed. In addition to the tandem gait, a normal gait can be performed to see if even that task is hindered.
Some patients will have ataxia to the lower body, some to the upper body, and others all over. With tests like tandem gait, doctors can measure dexterity in the lower body. Others, like the heel-to-shin test, has the seated patient attempting to place the heel of the foot on top of the other leg's knee — another difficult task for someone suffering from ataxia. Conversely, a finger-to-nose test, another component of many field sobriety tests, can help doctors gauge whether ataxia is thus far isolated to upper-body movements.
The tandem gait test is one of three main parts to many field sobriety tests. By walking in a heel-to-toe fashion while performing basic tasks like counting backward or just counting the steps, officers often can determine if a driver is impaired. Other parts of the test include a one-leg stand for a specified amount of time as well as analyzing the driver's eyes in a horizontal gaze nystagmus test. According to the U.S. National Highway Traffic Safety Administration, more than 90 percent of the time drivers who fail all three parts of the test are drunk. To confirm suspicions, of course, officers will then ask suspects to perform an even less-contestable blood or breath test.