Tic Disorders: Differential Diagnosis

Differential Diagnosis

Differential Diagnosis of Tics

Tics have many characteristics that differentiate them from the other movement disorders. Perhaps most important to “ruling in” tics as a diagnostic possibility is the childhood history of simple motor tics in the face. Other movement disorders do not have a similar pattern of movement onset or location. There are atypical presentations of tic disorders that may resemble other movement disorders, but these would be unusual and would probably re-quire a consultation with a movement disorders expert.

Movement disorders such as chorea and dystonia are con-tinuous movements and can be distinguished from tics, which are intermittent. Paroxysmal dyskinesias, although episodic, are more often characterized by choreiform and dystonic move-ments, which are different from tics. Myoclonic movements and exaggerated startle responses are also intermittent movements but are usually large-muscle movements that occur in response to a patient-specific stimulus. Complex tics can be more difficult to differentiate from other complex movements such as manner-isms, gestures, or stereotypies. In a person with clear-cut motor tics, it may be difficult to differentiate a complex motor tic from a “camouflaged” tic (making a simple tic appear to be a purposeful action, e.g., an upward hand movement that the person turns into a hair smoothing gesture), mannerism, gesture, or stereotypy. Mannerisms or gestures are often not impairing; stereotypies tend to occur exclusively in children and adults with develop-mental disabilities and mental retardation (Jankovic, 1992).

It is also possible to have a tic disorder and another move-ment disorder. For example, tic movements can cooccur with dystonia. Similarly, it is not uncommon in tertiary referral cent-ers to see developmentally disabled children and adults with both tics and stereotypes.