Motor disorders in neurodevelopmental disorders. Tics and stereotypies

Tics are repetitive, sharp, rapid, non-rhythmic movements or utterances that are the result of sudden, abrupt and involuntary muscular contractions. Stereotypies are repetitive, apparently impulsive, rhythmic, purposeless movements that follow an individual repertoire that is specific to each individual and that occur under a variable time pattern, which may be either transient or persistent. Both are included in the Diagnostic and statistical manual of mental disorders, fifth edition (DSM-5), among the neurodevelopmental disorders, and together with coordination development disorder go to make up the group of motor disorders. For tics, the categories of 'Tourette's disorder', 'chronic motor or vocal tic disorder' and 'unspecified tic disorder' have been maintained, whereas the category 'transient tics' has disappeared and 'provisional tic disorder' and 'other specified tic disorders' have been incorporated. Within stereotypic movement disorder, the DSM-5 replaces 'non-functional' by 'apparently purposeless'; the thresholds of the need for medical care are withdrawn and replaced with the manual's standard involvement criterion; mental retardation is no longer mentioned and emphasis is placed on the severity of the stereotypic movement; and a criterion concerning the onset of symptoms and specifiers of the existence or not of self-injurious behaviours have been added, together with the association with genetic or general medical diseases or extrinsic factors. Moreover, a categorisation depending on severity has also been included.