Functional movement is an unwanted muscle movement such as a spasm or tremor that is caused by an underlying psychological condition. A functional disorder can involve any part of the body and resemble the same muscle movements that occur with a biological condition or structural abnormality. Most functional movement is involuntary—done without being consciously initiated by the individual. It may develop as part of a conversion disorder (in which a psychological event causes physical symptoms with no known medical cause). It also may result from a somatoform disorder (characterized predominantly by multi-system symptoms that are associated with distress and/or dysfunction), factitious disorder (an illness that simulates symptoms for psychological reasons), or malingering (not characterized as a psychiatric disorder but where illness is pretended as a way to achieve a secondary goal such as the acquisition of drugs or disability benefits). Unlike movement disorders caused by biological or structural conditions, functional movement disorders commonly develop suddenly, progress rapidly to maximum severity, may increase in intensity, and come and go with complete or partial remissions. The movement may be less when the person is distracted, and the severity of symptoms varies among individuals. The course of the psychological condition may be short-lived or lead to chronic disability.
Functional movement is uncommon before the age of 10 years. In children, the dominant limb is most often affected, while adults most frequently see movement in the nondominant limb.
Psychogenic movement disorders include:
Functional tremor (also called functional tremor) can appear as any form of tremor movement. Characteristics may vary but generally include thythmic tapping, sudden onset and remission, increased incidence with stress, change in tremor direction and/or body part affected, and greatly decreased or disappearing tremor activity when the person is being distracted. Many individuals with psychogenic tremor have a conversion disorder.
Functional dystonia involves involuntary muscle contractions that cause slow, repetitive movements or abnormal postures that are often severely painful. Onset may be abrupt or appear as part of a recurring attack. Functional dystonia typically involves abnormal fixed postures, particularly from the start, whereas dystonia caused by a muscle or structural abnormality tends to involve more mobility and be action induced. There are patterns of movement that help diagnose the disorder.
Functional myoclonus refers to sudden, involuntary muscle contractions (twitches) or jerking of a muscle or group of muscles that are caused by a psychological condition or stimulus such as a tap or sound. Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. Exaggerated startle or startle-like movements are frequent. Functional myoclonus may occur spontaneously or be generated by an action (or anticipation of an action or sound) or reflex. The twitching cannot be controlled by the person experiencing it.
Funcitonal parkinsonism involves rigid movements that are extremely slow and often associated with a great sense of effort and rapid onset of severe fatigue. There can be a tremor at rest that does not resolve such as the tremor does in Parkinson's disease. Symptoms are usually seen on both sides of the body. There seems to be a high correlation of functional parkinsonism with general parkinsonism but the reason is unclear.
Functional gait disturbances feature unusual patterns of stance and gait. Individuals may stagger or veer from side to side when walking and appear to be losing their balance, but only rarely fall. The patient's balance tends to be much better than claimed. Sudden knee buckling without falling is common.
No single test can confirm functional movement, which can prove difficult to diagnose. Physicians must rule out co-existing conditions and other recognizable movement disorders. There may be fluctuations during a neurological exam—particularly an increase of movement following attention and suggestion (an external influence on the will of the patient), and a decrease when the person is distracted. Electromyography (EMG) may be used to measure bursts of electrical activity from the brain and/or spinal cord to a peripheral nerve root (found in the arms and legs) that controls muscles during contraction and at rest. Electroencephalography (EEG) can correlate the movement and detect any changes in electrical activity patterns produced by the brain. Physicians also look for marked improvement in symptoms following psychotherapy, use of a placebo (a medicine with no specific pharmacological benefit for the disorder being treated but given to see if it produces psychological or physical benefits), or suggestion. A multi-therapy approach to treating functional movement includes psychotherapy, placebo, or suggestion; antidepressants for symptoms related to depression or anxiety; cognitive-behavioral therapy to identify and alter thoughts and feelings that may be causing the psychological illness; physical therapy; and rehabilitative and occupational therapy to improve performance of activities of daily living. An experimental treatment is transcranial magnetic stimulation (TMS), which can alter electrical activity in the brain’s cortex (the region that controls movement) and may reduce movement frequency.
The severity of functional movement symptoms and prognosis varies among individuals. Prognosis is considered poor when the movement disorder continues for many years. Outcome appears to be better in younger people with a shorter duration of symptoms than in older persons with more chronic symptoms. Also, people with few and mild symptoms that have an acute onset tend to have a more favorable outcome, particularly if the duration of symptoms is relatively short and is preceded by a stressful or traumatic event. Some individuals may continue to experience symptoms over time and develop new symptoms related to other parts of their body.
Scientists at the National Institute of Neurological Disorders and Stroke are studying how the mind and the brain work to cause movement symptoms in people who have no known underlying neurological or medical disorder. Researchers are investigating risk factors and neurobiological markers of functional movement disorders (also called stress-related movement disorders). A number of biological and psychosocial factors may act together to bring on uncontrollable movements such as twitching, jerking, twisting or weakness of certain body parts. The study examines several genetic markers which are involved in stress and emotional disorders. It also assesses cortisol levels and heart rate variability as a measure of stress and autonomic nervous system functioning, and detailed psychological measures. Highly advanced brain imaging will detect changes in structures of the brain and the strength of fiber connections between certain brain areas. Findings in individuals with functional movement disorders will be compared to those of healthy volunteers. Functional magnetic imaging (fMRI) can detect altered blood flow that may reflect changes in activity between brain cells and is being investigated in indiiduals with psychogenic movements. Other researchers are exploring the role of biofeedback in lessening or stopping movement symptoms, and how different types of psychotherapy may help individuals who have somatoform disorders. Another study is evaluating the effects in functional status in individuals with functional gait disorder after three weeks of cognitive and behavioral rehabilitation. Follow-up studies after 1 and 12 months will evaluate if any improvement is still present. Information from the National Library of Medicine’s MedlinePlus Movement Disorders