Other movement disorders

Abstract

It is helpful to think of most movement disorders (other than akinetic, rigid and ataxic disorders) as forms of dystonia, chorea, tremor, tics or myoclonus. Dystonia is a sustained muscle contraction leading to repetitive movements or abnormal postures. Chorea takes the form of involuntary, abrupt, irregular and random movements, usually of the face, hands and feet. Tremor is a rhythmic oscillation of a body part produced by alternating or synchronous contraction of antagonistic muscles. Tics are rapid, brief jerks, usually of the head and arms. They can be suppressed for short periods at the expense of increasing tension and distress to the patient. Myoclonic jerks are brief, sudden, shock-like movements caused by active muscular contraction. Sudden pauses of muscular activity are termed ‘asterixis’; this is the basis of the ‘flapping tremor’ of various encephalopathic states. Most drug-induced movement disorders are caused by dopamine receptor-blocking agents. Hemifacial spasm may be mistaken for focal epilepsy or focal dystonia. The cause is usually microvascular compression of the facial nerve in the posterior cranial fossa; occasionally, there is a mass lesion in the cerebellopontine angle.