The onset is often related to a precipitating event, such as surgery, the death of a loved one, divorce, rape, or financial stress. "The person basically starts having a multitude of abnormal movements right after this precipitating event," said Hinson.
There are also typical clinical signs. For example, the movements tend to be incongruent with organic disease, and there may be multiple abnormal movements. "So I might see a patient who has tremor and myoclonus and chorea and on top of that, a speech and a gait disorder," said Hinson.
The movements tend to exhibit distractibility and variability and increase with attention to the affected body part. "The movements may vary throughout the examination," said Hinson. "When the examiner leaves the room, the movement improves, and when we pay special attention to the limb in question, the movement suddenly is exacerbated."
Other characteristics are deliberate slowness of movement; entrainment; coactivation; association with false weakness, sensory loss, and pain; lack of responsiveness to drugs for organic movement disorders; and response to placebo drugs and suggestion.
A simple way to check for entrainment is to have the patient mimic a movement at a specific frequency. "If the patient has a tremor in the left hand at a certain frequency, we have them do rapid alternating finger tapping movements with their right hand at a given frequency, and often times we will see that the psychogenic tremor will assume the frequency of the voluntary movement," said Hinson. A good test for distractibility, she said, is to have the patient count backward from 100 in sevens and see if this affects his movements.
Jankovic reported that he will sometimes use the power of suggestion to check for a PMD. For example, he might tell a patient with intermittent tremor that vibration can trigger the tremor in some patients and then apply a tuning fork to the affected part of the body. "In most cases, the patient suddenly develops tremor, even though it's not due to any organic cause, but just to my suggestion." He said that a converse suggestion also could work: suggesting that the tuning fork will reduce the tremor.
"I have hundreds and hundreds of videotapes that show complete resolution of the tremor with the power of suggestion," he said. This strategy helps define the phenomenology and provides further support for the diagnosis.
Another test that can be used to aid in diagnosis is the administration of a placebo. Hinson recommended giving placebos in a double-blind fashion—and only with the patient's consent, to avoid feelings of deception or mistrust. She also cautioned that organic movement disorders may temporarily improve in response to placebo administration, so placebo response should not be used as the sole criterion for a diagnosis of a PMD.
Kompoliti agreed that neurologists need to be cautious with these diagnoses. For example, she pointed out that it is possible for more than 1 movement disorder—such as Parkinson and chorea—to coexistent in the same patient. Furthermore, certain movement disorders, such as dystonia, can be bizarre in their presentation and their triggers.
Neurologists may need to perform tests such as MRI or spinal fluid analysis to exclude organic causes of the symptoms. However, said Jankovic, these tests usually already have been performed by the time he sees a patient at his center. "I rely on examination," he said. "There's no blood test that can tell someone they have PMD."
Neurologists also can use tests such as EMG-based tremor analysis and EMG analysis of myoclonus to quantify movement disorders. "With an EMG, you can document this entrainment phenomenon much more specifically than you can just visually because you can show the frequency of the tremor, you can show exactly the changes of frequency of the tremor with distraction," said Hinson, who noted that she rarely uses this test.
European physicians sometimes use functional brain scans such as [123I]-CIT single-photon-emission CT and fluorodopa positron emission tomography scans to check for dopaminergic cell loss in the brain, but these are used primarily in research settings in the United States.
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