Tourette's diagnosis is an exclusionary process. This means that doctors have to rule out all other causes of the patient's symptoms before they diagnose Tourette's. They use EEGs, MRIs and blood tests to test for other possible causes, which can include seizures, brain abnormalities, hyperthyroidism and movements induced by drugs.
Once they rule out all other possibilities, doctors diagnose Tourette's through determining the age of onset and observing movements. The tics must begin before the patient is 18 years old. Patients must display multiple motor tics and at least one vocal tic. The motor and vocal tics do not have to occur at the same time, but they both must be experienced in the same year. Within that year, the patient can't have more than three consecutive "tic-free" months.
If the patient does not meet these rather strict criteria, he may be suffering from another type of tic disorder. If he has motor tics (but not vocal tics) daily or week;y for more than a year, he may be diagnosed with a chronic motor tic disorder. If he has vocal tics but not motor tics, chronic vocal motor tic disorder could be the diagnosis. A person who displays both motor and vocal tics, but for less than a year, could have a transient tic disorder.
Several conditions, including obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD), have been linked with Tourette syndrome. In fact, because of the lack of definitive testing and the possibility of mild symptoms, doctors often diagnose Tourette's after a child has been diagnosed with OCD or ADHD. Learning and sleeping disorders are also common in with patients with Tourette's. Doctors often diagnose these conditions first because they cause a disturbance, or impairment, in the patient's life.
Scientists continue to study the link between ADHD and Tourette's and between OCD and Tourette's. Some studies suggest that patients with Tourette's are 20 times more likely to display the symptoms of OCD. In addition, relatives of Tourette's patients have high rates of OCD, and OCD patients have a higher chance of having a child with Tourette's syndrome. All of these factors lead scientists to suspect a similar genetic component for each of the disorders. While OCD and Tourette's have a rather clear genetic relationship, ADHD and Tourette's don't seem to have such obvious ties. However, it has been shown that more than 25 percent of patient's with Tourette's also suffer from ADHD.
After diagnosis comes treatment. See what works in treating Tourette's.