Hyperkinesia, dystonia, and tics

Movement disorders can be classified into two broad categories of akinetic/rigid and hyperkinetic disorders. Hyperkinetic movement disorders (hyperkinesias) are manifested by abnormal, uncontrollable, and unwanted movements. Hyperkinesias include different phenotypic categories, which can appear in isolation or in variable combinations [1]. Some conditions combine hypokinetic and hyperkinetic features, as exemplified by the coexistence of bradykinesia and tremor in Parkinson’s disease (PD) or levodopa-induced dyskinesia in patients with PD and chorea or dystonia in patients with Huntington’s disease, many of whom have an underlying hypokinesia. The crucial role of the basal ganglia is increasingly recognized, not only in hyperkinetic movement disorders, but also in motor control, muscle tone, posture, behavior, and cognition. Although at first sight involuntary movements resemble each other, each hyperkinetic disorder has a specific phenomenology (signature) that can be identified by direct observation of the patient or videotaped examination. Duration, rhythmicity, topography, and other features must be carefully analyzed and noted in order to make a specific phenomenological diagnosis. The hallmark features and phenomenology of the main hyperkinetic disorders are reported in Table 18.1, and a detailed review can be found in [1]. Phenotypic categories of hyperkinesia As previously mentioned, the main phenotypic categories of hyperkinesias are: Tremor, chorea, tics, myoclonus, dystonia, and stereotypies. In addition to these six categories there are other abnormalities of motor control that are also included within the field of movement disorders, such as akathisia, amputation stumps, ataxia, athetosis, ballism, hyperekplexia, mannerisms, myorhythmia, restlessness, and spasticity. The term “dyskinesia” is commonly used to indicate any or a combination of abnormal involuntary movements, such as tardive or paroxysmal dyskinesias or levodopa-induced dyskinesia, but more specific phenomenological categorization should be used whenever possible.