Psychogenic movement disorders (ORPHA:71519)
A rare neurologic disease characterized by the manifestation of an underlying psychiatric illness or malingering, and that cannot be attributed to any known structural or neurochemical diseases. Most cases fall in the psychiatric diagnostic category of conversion disorder, also referred to as functional neurological symptom disorder.
Epidemiology
The exact prevalence of psychogenic movement disorders (PMD) is unknown. At tertiary care centers, 2-4% of movement disorders patients are diagnosed with PMD.
Clinical description
PMD present typically during adolescence or adulthood. Childhood cases and new onset in the elderly are rare, but do occur. Symptoms may include one or several types of abnormal movements seen in organic movement disorders (tremor, dystonia, chorea, bradykinesia, myoclonus, tics, athetosis, ballism, cerebellar incoordination), and also affect speech and gait. Typically, PMD present with complex movements of multiple different phenomenologies, usually incongruent with an organic movement disorder and affecting several body regions. Tremor appears to be the most commonly observed phenomenon, followed by dystonia, bradykinesia, myoclonus, and other unclassifiable abnormal movements. Symptoms often occur abruptly, and maximal symptom severity and disability are reached quickly. Other typical features are: deliberate slowness of movement, distractibility, variability, suggestibility, paroxysmal symptoms, and resolution with placebo administration or when the patient is unaware of being observed. Frequently, PMD are accompanied by other psychogenic symptoms such as false weakness, sensory findings, or excessive pain. Depression and anxiety are common comorbidities.
Etiology
Underlying causes for PMD fall into three categories: Conversion disorder (also referred to as functional neurological symptom disorder), somatic symptom disorders, or, in rare cases, factitious disorder, and malingering. Risk factors include female gender, history of childhood trauma or sexual abuse, previous injury, surgery, and major stressful life events.
Diagnostic methods
The diagnosis is usually made on clinical grounds, but certain ancillary tests may be helpful. Electromyography-based tremor and myoclonus analysis can be used to distinguish psychogenic tremor and myoclonus from their organic counterparts. Neuroimaging in the form of [123 I]-beta-CIT SPECT and [18F]-DOPA-PET is sometimes used in difficult to diagnose cases of psychogenic parkinsonism to exclude an organic etiology.
Differential diagnosis
The differential diagnosis of PMD lies in the organic counterparts of each individual presenting abnormal movement. In cases of tremor as the presenting symptom for example, Parkinson's disease and essential tremor will be considered. Some patients with PMD have movements that resemble seizures, and epilepsy should be ruled out.
Antenatal diagnosis
Prenatal diagnosis does not exist for this disorder.
Management and treatment
Avoidance of iatrogenic damage by unnecessary invasive tests or inappropriate medications, early and precise diagnosis, and the facilitation of the appropriate psychiatric and physical rehabilitation treatment are important. Clinical trials are sparse, but the available literature suggests that a combination of psychotherapy with individualized psychiatric medication (aimed at treating coexisting conditions such as depression or anxiety) may be beneficial. Some centers also offer interdisciplinary inpatient programs, combing intense physiotherapy with psychotherapy.
Prognosis
The prognosis of PMD is variable, but is better than that for patients with other somatoform complaints such as sensory symptoms, weakness or pain. The presence of psychiatric comorbidity (depression or an anxiety disorder) is a positive prognostic factor. Long-standing symptoms, insidious onset of movements and primary psychiatric diagnosis of hypochondriasis, a factitious disorder, or malingering are negative prognostic factors. If left untreated, PMD tend to be chronic, and follow-up data in several series show persistent symptoms in 65-95% of patients.

                            Last update: 
                            November 2019


                            - Expert reviewer(s): 
                            Dr Vanessa HINSON