Tourette's syndrome daignostic parameter

both multiple motor tics and one or more vocal tics must be present at the same time, although not necessarily concurrently;

• the tics must occur many times a day (usually in bouts) nearly every day or intermittently over more than 1 year, during which time there must not have been a tic-free period of more than 3 consecutive months;

• the age at onset must be less than 18 years;

• the disturbance must not be due to the direct physiological effects of a substance (e.g. stimulants) or a general medical condition (e.g. Huntington's disease or postviral encephalitis).