Tourette syndrome (TS) is a diagnosis that doctors make after verifying that the patient has had both motor and vocal tics for at least one year. The existence of other neurological or psychiatric conditions like childhood-onset involuntary movement disorders, such as dystonia; or psychiatric disorders characterized by repetitive behaviors/movements (for example, stereotypic behaviors in autism and compulsive behaviors in obsessive-compulsive disorder-OCD), can also help doctors arrive at a diagnosis. Common tics are diagnosed easily by knowledgeable clinicians. However, atypical symptoms or presentation (for example, onset of symptoms in adulthood) may require specific specialty expertise for diagnosis. There are no blood or laboratory tests needed for diagnosis, but neuroimaging studies, such as magnetic resonance imaging (MRI), computerized tomography (CT), and electroencephalogram (EEG) scans, or certain blood tests may be used to rule out other conditions that might be confused with TS.
Patients usually obtain a formal diagnosis of TS only after symptoms have been present for some time. The reasons for this are many. For families and physicians unfamiliar with TS, mild and even moderate tic symptoms may be considered inconsequential, a part of a developmental phase, or the result of another condition. For example, parents may think that eye blinking is related to vision problems or that sniffing is related to seasonal allergies. Many patients are self-diagnosed after they, their parents, other relatives, or friends read or hear about TS from others.
This information is based on source information from the National Institute of Neurological Disorders and Stroke.