Because of their unusual presentation and coexisting neurological and psychiatric pathology, psychogenic movement disorders (PMD) are a diagnostic and treatment challenge for the neurologist. The term "psychogenic" refers to movement disorders that cannot be attributed to any known structural or neurochemical diseases but represent the manifestation of an underlying psychiatric illness. Physical symptoms can mimic the full spectrum of organic abnormal involuntary movements, affect gait and speech, or present as bizarre undifferentiated movements.

EPIDEMIOLOGY
The reported prevalence of psychogenic disorders in the general neurological population ranges between one percent and nine percent.1,2 Specific prevalence numbers for PMD are not well documented, but range around three to four percent in tertiary movement disorders centers. The mean age of onset of PMD is between 37 and 50 years of age, and women are predominantly affected.3,4,5 Several risk factors for PMD have been identified and include a history of sexual abuse, previous surgery, or other physical trauma.2,4,6

DIAGNOSIS
PMD are not merely a diagnosis of exclusion but are based on specific diagnostic criteria. At present, these criteria are largely based on a typical constellation of historical and clinical findings but can sometimes be supported by ancillary tests (Table 1).

Patient history. Important clues from the history include abrupt onset of symptoms, temporal relationship to a precipitating event, fluctuating or paroxysmal symptoms, and fast rate of progression.6 Because of their dramatic mode of onset, PMD can present as a movement disorder emergency and make up one of the few scenarios where the movement disorders specialist will be consulted by the hospital emergency department.

Neurological examination. Abnormal movements in PMD can mimic the full spectrum of movements seen in movement disorders of organic origin (tremor, dystonia, chorea, bradykinesia, myoclonus, tics, athetosis, ballism) and also affect speech and gait. Of note, PMD often present with a combination of different types of abnormal movements affecting several body regions. Hyperkinetic movements such as tremor and dystonia, as well as disorders of gait and speech are most common, whereas hypokinesia such as psychogenic parkinsonism is rare.5 Careful examination will reveal that the phenomenology is not congruent with an organic etiology. Other findings suggesting psychogenicity are deliberate slowness of movement, distractibility, and variability. In cases of psychogenic tremor, the "entrainment" and "coactivation" signs are often present.7 Entrainment refers to psychogenic tremor assuming the frequency of a voluntary movement executed by a different body part. Coactivation refers to increased muscle tone in the tremulous extremity that is inconsistent during the examination and can be overcome with passive movement.

Abnormal gait is frequently encountered in PMD. Psychogenic gait disorders are typically characterized by exaggerated effort and slowness, bizarre uneconomic postures, convulsive shaking episodes, sudden knee buckling, and near falling.8 PMD are often accompanied by other psychogenic neurological symptoms, such as false weakness or sensory findings, or by excessive pain and tenderness. Patients with PMD are often highly suggestible and respond to placebo therapy.9 Organic movement disorders however, can transiently improve with placebo, and a diagnosis of PMD should not be made based on the placebo response alone.

Levels of diagnostic certainty. Based on criteria developed by Fahn and Williams,4 PMD is considered "documented" when movements are relieved by psychotherapy, suggestion, or placebo and "clinically established" when movements are inconsistent or incongruent with organic disease and associated with other false neurological signs, multiple somatizations, or a documented psychiatric illness.

ANCILLARY TESTING
The diagnosis of PMD is mainly clinical, but ancillary testing can be useful in some difficult-to-diagnose cases.10 (Table 1) Functional neuroimaging with [123 I]â-CIT SPECT and [18F]DOPA-PET, for example, has been used to exclude Parkinson's disease in cases of psychogenic tremor. In addition, there are several neurophysiological tests that positively reinforce the diagnosis of PMD. Electromyography (EMG) based tremor analysis in PMD can demonstrate the entrainment and coactivation phenomena, an increase of tremor amplitude and frequency with weight loading of the tremulous extremity, variability in tremor frequency, and co-activation of antagonist muscles.7,11 EMG evaluation of psychogenic myoclonus shows abnormally long and variable latencies between stimulus and myoclonic jerk, variable patterns of muscle recruitment, prolonged duration of myoclonic bursts, as well as significant habituation with repeated stimulation.12

PSYCHIATRIC DIAGNOSIS
The DSM IV13 identifies three pertinent diagnostic categories for PMD: somatoform disorders, factitious disorders, and malingering. Somatoform disorders encompass conversion disorders (physical symptoms that are brought on by psychological stressors), as well as somatization disorders (a multitude of physical, non-organic symptoms). Factitious disorders refer to symptoms that are intentionally produced with the purpose of achieving some psychological gain, whereas malingering is the intentional symptom production for a material gain. Conversion disorder is the most common psychiatric diagnosis for PMD.4 PMD are frequently associated with other axis I psychiatric disorders; most commonly depression and anxiety.

PATHOPHYSIOLOGY
The pathophysiology of PMD remains unclear, but recent advances in neuroimaging allowed for initial investigations of underlying mechanisms. Spence, et al.14 used Positron emission tomography (PET) imaging to investigate the pathophysiology of psychogenic motor symptoms, compared to mechanisms involved in "feigning" the same symptoms. Measurements of regional cerebral blood flow (rCBF) showed relative hypoactivity of the left dorsolateral prefrontal cortex when attempting to move the affected limb in subjects with psychogenic disorders compared to feigners and normal controls. Marshall and colleagues15 evaluated a patient with left sided psychogenic paralysis using PET scanning and found a failure to activate the right primary motor cortex and an overactivation of the right orbitofrontal and anterior cingulate cortex. Finally, a study by Vuilleumier and colleagues16 with Tc-99m SPECT compared rCBF from patients with psychogenic sensorimotor paralysis before and after recovery. rCBF was decreased in the thalamus and basal ganglia contralateral to the deficit in the psychogenic subjects with a vibratory stimulation task. Importantly, these abnormalities resolved with clinical recovery, suggesting that conversion disorders may entail functional disorders in striatothalamocortical circuits controlling sensorimotor function and voluntary motor behavior.

TREATMENT
Delivery of the diagnosis. Most neurologists have experienced the scenario of making a diagnosis of psychogenicity that is met by vehement resistance on the part of the patient or the family. This is partly based on misconceptions of what constitutes PMD and the stigma associated with psychiatric illness. Patients often mistake this diagnosis as being told that there is "nothing wrong" or that the symptoms might be feigned or deliberate, resulting in physician mistrust and resistance towards psychiatric treatment.

There are several useful strategies for an empathetic and unambiguous delivery of the diagnosis. The specific movement disorder diagnosis based on the primary movement phenomenology (e.g. tremor, dystonia) should be disclosed (thus validating the patient's symptoms), and the underlying etiology (PMD) clearly discussed in layman's terms.

The interaction between body and mind should be mentioned and further illustrated with examples outside of PMD, such as the link between stress and gastric ulcers, or anxiety and perspiration. It is also important to point out the potential for better outcome in PMD compared to organic neurodegenerative diseases. The patient needs to understand that PMD is a psychiatric disorder with neurologic symptoms and that the treatment will require an interdisciplinary approach. The role of the psychiatrist will be to treat the underlying cause, whereas the neurologist will monitor physical symptoms.

Principles of treatment. The appropriate psychiatric treatment is based on a precise diagnosis of the pertinent diagnostic category for PMD (somatoform disorder, factitious disorder, or malingering) and recognition of secondary psychiatric illnesses. Treatment of coexisting depression or anxiety can improve physical symptoms.1 Clear guidance as to the best psychiatric treatment modality specific to PMD is lacking, but many use a combination of psychotherapy and pharmacotherapy.

An open label trial of citalopram and paroxetine17 showed marked improvements on both motor and global outcomes in patients with primary conversion disorder and PMD. Patients with primary hypochondriasis, somatization, factitious disorder or malingering did not improve with the intervention.

Data from a single-blinded clinical trial18 supports the combination of psychotherapy with psychotropic medication. Ten PMD patients treated with psychodynamic psychotherapy and antidepressant or anxiolytic medication improved significantly in regards to motor scores, measures of depression, anxiety, and global function improved.

Cognitive Behavioral Therapy (CBT) also has a role in the management of functional somatic symptoms. The goal of CBT is to reduce symptoms, perceived stress and disability and limit the inappropriate use of medical care.19 A controlled trial in the use of CBT for "medically unexplained physical symptoms"20 studied 79 subjects and randomized them to receive either CBT or "optimized medical care." The CBT intervention group had less impairment of sleep, a lower mean intensity of physical symptoms, and a higher recovery rate.

Other less established treatment modalities for PMD include hypnosis21 and biofeedback. Of note, any of these therapies can be combined with a rehabilitative physical therapy program for maximal benefit.

PROGNOSIS
The outcome of PMD therapy is variable, but in general better than in patients with other somatoform complaints such as sensory symptoms, weakness or pain.1 A comorbid psychiatric diagnosis of depression or anxiety has been found to be a positive prognostic factor for the outcome of PMD.6 Negative prognostic value has been associated with long-standing symptoms (greater than six months), insidious onset of movements and primary psychiatric diagnosis of hypochondriasis, factitious disorder, or malingering.3,17 Other commonly encountered obstacles to treatment success are patient resistance towards the diagnosis of psychogenicity and lack of willingness to engage in psychiatric treatment.22 If left untreated, PMD tend to be chronic. Follow-up data in several series show persistent symptoms in 65-95 percent of patients,3,4,6 clearly demonstrating the need for effective early intervention strategies.

Dr. Hinson has received compensation and grant support from Teva, Allergan, and Solstice.

Vanessa K. Hinson, MD, PhD is Associate Professor of Neurology. Medical University of South Carolina in Charleston and Acting Chief of Neurology, Ralph H. Johnson VA Medical Center in Charleston, SC.

*"Winds from the wings of madness" is a quote from Charles Baudelaire.