Tourette Syndrome - Classification

Classification

Tics are sudden, repetitive, nonrhythmic movements (motor tics) and utterances (phonic tics) that involve discrete muscle groups. Motor tics are movement-based tics, while phonic tics are involuntary sounds produced by moving air through the nose, mouth, or throat.

Tourette's is one of several tic disorders, which are classified by the Diagnostic and Statistical Manual of Mental Disorders (DSM) as "disorders usually first diagnosed in infancy, childhood, or adolescence" according to type (motor or phonic tics) and duration (transient or chronic). Transient tic disorder consists of multiple motor tics, phonic tics or both, with a duration between four weeks and twelve 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 (DSM-IV 307.23) is diagnosed when multiple motor tics, and at least one phonic tic, are present for more than a year. The fifth version of the DSM (DSM-5), due out in May 2013, is likely to reclassify Tourette's as a neurodevelopmental disorder, and to include additional diagnoses to account for tic disorders due to substance abuse or other general medical conditions.

Tic disorders are defined only slightly differently by the World Health Organization International Statistical Classification of Diseases and Related Health Problems, ICD-10; code F95.2 is for combined vocal and multiple motor tic disorder .

Although Tourette's is the more severe expression of the spectrum of tic disorders, most cases are mild. The severity of symptoms varies widely among people with Tourette's, and mild cases may be undetected.