Functional movement disorders represent a challenge for the clinical practitioner as the diagnosis and treatment are usually difficult, and the prognosis may be poor in some patients. Sometimes also referred to as “functional,” “conversion,” or “psychogenic,” these disorders must be differentiated from “organic” disorders. Functional movement disorders may have several presentations, including tremor, dystonia, myoclonus, tics, parkinsonism, gait disorders, hemifacial spasm, opsoclonus, oculogyric crisis, stereotypies, painful legs, moving toes, etc. and are not uncommonly accompanied by functional speech and voice disorders. In this article, the author discusses current advances in the diagnosis, pathophysiology, and treatment of functional movement disorders.
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• There is currently a lively debate whether the term functional or psychogenic should be used to describe these movements, with both terms having advantages and disadvantages.
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• Functional movement disorders may have a wide variety of presentation; although tremor, dystonia, myoclonus, and gait disorders are among the most common, tics, parkinsonism, abnormal ocular movements, palatal tremor, stereotypies, and hemifacial spasm can also be observed.
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• The diagnosis of functional movement disorders should be based on positive clinical findings rather than being a diagnosis of exclusion.
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• The prognosis of functional movement disorders is usually poor; however, a short duration of the symptoms with an acceptable explanation and understanding of the disorder by the patient are considered important good prognostic factors.
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• Current advances in the use of functional brain imaging are providing further information about the pathogenesis of these conditions.
Historical note and terminology
The term hysteria was introduced in the Corpus Hippocraticum by Hippocrates of Kos (460-370 B.C.) to explain gynecological and other medical symptoms that were suspected to be linked with the womb (uterus). In the following centuries the concept of a “wandering womb” causing neurologic and psychiatric symptoms was predominant (203). However, in the second century Galen of Pergamon (130-210 A.D.) developed a theory emphasizing reciprocal influences between the mind and body to explain neuropsychiatric manifestations; however, such a remarkable advance was not further developed and in the Middle Ages “hysteria” was considered a sign of witchcraft and punished according to the instructions provided by the influential book Malleus Maleficarum: this view was dominant until Edward Jorden (1569-1633) recognized hysteria as a mental illness in his book A Disease Called the Suffocation of Mother (203). The conception of hysteria was not deeply studied until Pierre Briquet (1796-1881) published his book Traité clinique et thérapeutique de l’Hystérie, where he rejected theories attributing the neuropsychiatric symptoms to the womb. Briquet’s work had a great influence on Jean-Martin Charcot (1825-1893), who headed the French school in La Salpêtrière in Paris (81).
Charcot developed the anatomo-clinic method to study neuropsychiatric disorders through correlation between neurologic symptoms and abnormal pathology. Charcot discriminated disorders with an “organic” cause (ie, those with identifiable lesions in the nervous system) to those without an identifiable pathological lesion, called nevroses (neuroses), which included hysteria (81). Charcot dedicated several of his last years to the study of hysteria and proposed that hysteria was congenitally derived and a “dynamic lesion” from which its nature was unknown affected specific areas of the nervous system correlating with symptoms (81). He also used hypnosis as an experimental method to study hysterics; such proceedings are depicted in the famous painting “Une leçon clinique à la Salpêtrière” by Andre Brouillet. Charcot believed that prompt treatment of hysterical symptoms was important for good outcome and encouraged induction of second attacks using “hysterogenic points” or hypnosis for the diagnosis and treatment of many neurologic complaints. Many criticized this approach to treatment, as it would lead to imitations and behavior reinforcement. The English school headed by Gowers and Henry Head was critical on this point. Gowers observed that neurotics might suffer from many symptoms including spasm, palsy, and coma. He emphasized that there were few organic brain diseases not “imitated” by neurosis and the clinician must exclude any potential organic cause for the symptoms before concluding that they are functional in origin (83; 92).
Charcot and his followers used hypnosis as a powerful tool for demonstrating how, on occasion, subconscious motivations could generate a variety of disabilities resembling those seen in the context of bona fide neurologic disease (71). At that time, Janet emphasized the concept that “fixed ideas” could act in an unconscious level, and such unconscious mind may “dissociate” from the conscious mind under certain circumstances such as hypnosis or emotional states (186). Following the same line of thought, the term “hysteria” was replaced by “conversion” disorders, under the influence of Sigmund Freud who proposed that these symptoms result from a transformation (or conversion) of a psychological conflict into a symbolic physical manifestation because of repression of the unconscious mind, related to sexual conflicts (104). By the end of the 19th century Joseph Babinski, a Charcot’s student, aimed to identify clinical signs that distinguish “conversion” from organic disorders. He introduced the term “pithiathism” (from the Greek “persuasion”) following the observation that suggestion is characteristic in these patients (219; 188). Conversion disorders have been classified under the somatoform disorders (Briquet syndrome), a group of longstanding poly-symptomatic manifestations without evidence of an organic origin. Currently, the term "functional" is used to describe abnormal movements believed to derive from an underlying psychological or psychiatric disorder (88). However, a substantial proportion of patients with a movement disorder labeled "functional" does not always fit into an established psychiatric diagnosis (such as personality disorders, neurotic tendencies, or psychotic states), puzzling clinicians because of their apparent lack of appropriate characteristic psychosocial features or evidence for secondary gain (168). For these reasons some authors have proposed the term “functional movement disorders” (48); however, this term may also be misleading in part because patients suffering from these disorders are quite dysfunctional rather than functional (100). Furthermore, the term “functional” is not easily understood by patients, lacks scientific specificity, can be a disservice for patients, and it may delay treatment; but more importantly, the term functional could be a tactful way to lead the patient to acceptance of the diagnosis and to provide proper therapy (60; 100). In this review, we will use the term “functional” rather than “psychogenic,” but both terms are currently used in modern literature.
The DSM-5 (03) classification of psychiatric disorders includes additional categories under which a functional movement disorder might reside, such as somatic symptom disorder, conversion disorder, illness anxiety disorder, and factitious disorders. In a minority of cases, the primary psychiatric disorders are factitious disorders or malingering, in which the abnormal movements are feigned (26; 02). However, the term “malingering,” has been removed from DSM-5 as it is thought to represent a voluntary condition rather than a mental illness.