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Tic disorders are defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM) based on type and duration of tics, as follows:
- Transient tic disorder consists of multiple motor and/or phonic tics with duration of less than 12 months.
- Chronic tic disorder is either single or multiple motor or phonic tics, but not both, which are present for more than a year.
- Tourette's disorder is diagnosed when both motor and phonic tics are present for more than a year.
- Tic Disorder NOS is diagnosed when tics are present, but do not meet the criteria for any specific tic disorder.
DSM-IV-TR diagnosis codes for the tic disorders are:
- 307.20 Tic Disorder NOS (Not Otherwise Specified)
- 307.21 Transient Tic Disorder
- 307.22 Chronic Motor or Vocal Tic Disorder
- 307.23 Tourette's Disorder
ICD10 diagnosis codes are:
- F95.0 Transient tic disorder
- F95.1 Chronic motor or vocal tic disorder
- F95.2 Combined vocal and multiple motor tic disorder [de la Tourette]
- F95.8 Other tic disorders
- F95.9 Tic disorder, unspecified
Tourette syndrome is the more severe expression of a spectrum of tic disorders, which are thought to be due to the same genetic vulnerability. Nevertheless, most cases of Tourette syndrome are not severe. Although a good body of investigative work indicates genetic linkage of the various tic disorders, further study is needed to confirm the relationship. (Swerdlow, 2005 and Black)