[Clinical and cognitive aspects of functional (psychogenic) tremor]

Functional (psychogenic) tremor is the most common functional movement disorder. Characteristic clinical features, so called red flags, can help to make the clinical distinction of this type from other tremor disorders. The most common features include the variability of frequency and amplitude. Clinical examination should include different types of distraction including motor or cognitive tasks or testing the influence of suggestibility on tremor amplitude, frequency or direction. Patients often report sudden onset and remissions that may last for months or even years. In some cases, the tremor is only present in highly specific situations. Although functional tremor shares characteristics with voluntary actions, patients experience their abnormal movements as involuntary. Recent experimental approaches have revealed an impairment in sense of agency. The diagnosis can be supported by neurophysiological measurements including accelerometry, which achieved a sensitivity of 89.5% and a specificity of 95.9% in a validated test battery, thus providing a useful additional diagnostic tool. Psychotherapeutic treatment is indicated in patients with and without evident psychological symptoms. A specific physiotherapeutic approach for functional tremor is re-trainment.