An Update on Functional (Psychogenic) Tremor

Abstract

Functional tremor accounts for at least 50% of patients with functional movement disorders. The diagnostic work-up of these patients can be challenging. It is a multistep process based on patients' history and clinical criteria finally providing a 'positive' diagnosis. Variability of the tremor over the disease course and during clinical examination is characteristic. Patients often show increased attention toward the tremulous body part and distractability of the tremor once attention is drawn away. Sometimes distractability becomes obvious during history taking or neurological examination, in others certain distraction tasks are needed. If uncertainty remains, ancillary investigations such as electrophysiological tests may be helpful. Recent studies suggested that a loss of sense of control of ones actions may help to explain why patients with functional tremor report that they do not experience the abnormal movement as voluntary. Treatment has to be placed in a multidisciplinary team involving neurologists, psychiatrists, physiotherapists and psychologists. KEYWORDSFunctional (or psychogenic) movement disorders (FMD) are part of a wide spectrum of functional neurological disorders and account for 2-20% of movement disorders in specialized clinics [1,2].FMD can resemble all organic involuntary movements, affect gait and speech or present as unusual undifferentiated movements that do not fit into a known category [3]. Historically, FMD were thought to be caused by emotional trauma and were diagnosed by excluding organic disorders. There has been an ongoing debate concerning the preferable terminology [1]. Descriptive terms such as psychogenic, conversion or somatization disorders were proposed, other experts suggested nonorganic or medically unexplained disorders, hysteria or functional disorders.Recent epidemiological studies questioned the relevance of psychological triggering factors [4] and most movement disorder neurologists do not consider them mandatory for a diagnosis of FMD [5]. This paradigm shift has also found acceptance among psychiatrists and the DSM5 criteria for conversion disorder (functional neurological symptom disorder) have been modified to emphasize the essential importance of the neurological examination, and in recognition that relevant psychological factors may not be demonstrable at the time of diagnosis [6].Over the last decades the diagnosis of an FMD has shifted from excluding an organic movement disorder to providing a 'positive' diagnosis. A modified definition for FMD was recently proposed as "a movement disorder that is significantly altered by distraction or nonphysiological manoeurvres (including dramatic placebo response) and that is clinically incongruent with movement disorders known to be caused by neurological disease [1]".Among patients the term 'functional' has been shown to be most acceptable and subsequently many movement disorder specialists now prefer this term because it does not presuppose a cause for For reprint orders, please contact: reprints@futuremedicine.com