Psychogenic tremor and related disorders.

Psychogenic tremor is the most common form (55%) of all psychogenic movement disorders. Almost 75% of presenting patients are female. Onset is often abrupt. Preceding events include work related injuries and other accidents. Important clinical characteristic include variability of direction, amplitude and frequency. A positive entrainment test, presence of the co-contraction sign, absence of finger tremor and slowness of voluntary movements are suggestive of psychogenic origin. Co-morbidity with psychiatric disorders is common and includes somatoform disorders (35%), such as pain, diffuse sensory loss, conversion disorders and depression (14%). One fifth (21%) of patients are involved in litigation or compensation issues. Diagnosis is based on history, clinical signs and investigations. A multimodal approach including neuropsychiatric evaluation and psychotherapy should be offered. Prognosis, however, is relatively poor particularly if the condition has persisted for over a year and in the long-term up to 80-90% of patients continue to have abnormal movements.