A functional movement disorder (FMD) is a problem with body movement that doesn’t have a clear physical cause, such as nerve damage. It used to be called psychogenic movement disorder. It's a type of functional neurological disorder.
An FMD may cause shaking, twitching, tremors, clenching, slow movement, weak feeling, or stiffness. The symptoms may start suddenly. It will feel like you can’t control the symptoms. They may get worse when you pay attention to them. And they may decrease when you are distracted from them.
There are different types of FMDs. They include:
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Functional tremor, which causes shaking in certain body parts
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Functional dystonia, which causes muscle contractions and severe bending of joints
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Functional gait, which causes problems with the way you walk
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Functional myoclonus, which causes quick muscle jerks
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Functional Parkinsonism, which causes shaking and stiffness
What causes functional movement disorders?
Researchers don’t know yet what causes them. Tests don’t show clear physical causes, such as nerve damage. The problem may be because of changes in how the brain processes signals after different kinds of stress. Signals from the brain sent to muscles may be disordered. An FMD may occur within a few months after a stressful illness or injury. People who have had a history of severe stress from sexual abuse, bullying, anxiety, or depression may be more at risk for an FMD.
Symptoms of functional movement disorders
Symptoms depend on the type of FMD:
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Functional tremor. This causes shaking movement you feel you can’t control. It may be in a hand, leg, or your whole body. It may start suddenly, and only on one side of your body. Another part of your body may shake if you try to stop the shaking. But it may stop if you are distracted in certain ways. It may get worse over time.
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Functional dystonia. You may have muscle contractions that you feel you can’t control. This may cause your foot or arm or another part of your body to bend or twist. This may cause pain in those areas.
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Functional gait. This type of FMD affects the way you walk (gait). Your gait may be slow or stiff. Or you may move your arms and body a lot when walking and not be able to control it. You may only be able to take small, careful steps. Your knees may feel weak and about to give way (buckle).
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Functional myoclonus. These are quick muscle contractions that feel like a sudden jerk, shake, or spasm. Or a body part may feel suddenly weak for a short time. This problem may come and go over time.
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Functional Parkinsonism. This type of FMD causes symptoms like Parkinson disease. These include tremors and muscle stiffness at rest, and slowness when moving. But the symptoms decrease with distraction, unlike Parkinson disease.
Diagnosing functional movement disorders
Your healthcare provider will ask you about your symptoms. They will ask about your health history, and any injury, illness, or life stress that you had in the last few months. You may have tests to look for problems in your brain or nerves. Tests, such as surface EMG and electroencephalography, look at how electrical signals move through your brain and nerves. You may also have an imaging test of the brain, such as an MRI or SPECT. Tests will likely not show any clear signs of a disease. Diagnosis is made by noting a set of criteria, such as sudden start of symptoms, and symptoms that lessen with distraction.
Treatment for functional movement disorders
FMD is a complex condition. Researchers are still learning about FMDs. There is no 1 treatment that works for everyone. Your treatment depends on the type of FMD you have, and what your healthcare provider thinks may help you best. You may be referred to a movement disorders clinic that treats FMDs. Treatments that can help include:
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Physical therapy
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Occupational therapy
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Cognitive behavior therapy
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Psychotherapy
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Medicine to help with anxiety, depression, or other mood disorders
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Stress management methods
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Transcranial magnetic stimulation
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Exercise
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Hypnosis
Living with a functional movement disorder
An FMD can cause a lot of distress. The symptoms can cause pain and problems with daily life. They may be hard to treat. They may not go away over time. In some cases, they may get worse over time. Ask your healthcare provider about support groups in your area.
When to call your healthcare provider
Call your healthcare provider if any of the following occur:
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Symptoms that don’t get better, or get worse
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New symptoms
