The relation of transient tic disorder (TTD - motor or vocal tics lasting less than 1 year) to Tourette's syndrome (TS multiple motor and vocal tics lasting longer than 1 year) has been evaluated in two Canadian Mennonite families at the Dept of Neurology, Univ of Rochester Sch of Med, NY. One girl aged 9 yrs experienced frequent repetitive throat clearing and eye blinking episodes that resolved after several months (TTD). Her father and brother had TS and 2 siblings had chronic tic disorder (CTC-motor or vocal tics, but not both, with duration more than 1 year). A boy aged 12 yrs had frequent head jerks resolving over several months (TTD). His father had TS and sibling had CTD. In adulthood, the patient had 3 chldren, one with TS, [1].

COMMENT. Transient tic disorder may be an expression of the TS gene that may be transmitted to offspring as an autosomal dominant. The frequency of transient tics in childhood is quoted at 4-16%. The observations in this study suggest that TS and related tic disorders are more prevalent than generally appreciated.