Tic
A tic is a sudden, repetitive, nonrhythmic motor movement or vocalization involving discrete muscle groups. Tics can be invisible to the observer, such as abdominal tensing or toe crunching. Common motor and phonic tics are, respectively, eye blinking and throat clearing.
History of Tourette syndrome
TS was first included in the third revision of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-III) in 1980. In 2000, the American Psychiatric Association published the DSM-IV-TR, revising the text of DSM-IV to no longer require that symptoms of tic disorders cause distress or impair functioning. The fifth revision of the DSM (DSM-5) was published in 2013: it defined tic disorders in the motor disorders chapter of the neurodevelopmental disorders, and removed the word "stereotyped" from the description of tics; replaced transient tic disorder with provisional tic disorder; differentiated motor and vocal chronic tic disorder; removed the use of stimulants as a cause of tics; and e) added two new categories of tic disorders. Few significant other changes were made.