When trying to diagnose REM sleep behavior disorder, or RBD, the neurologic exam is often normal. However, symptoms and signs of Parkinson's disease, such as hand tremor at rest, slowness in movement, and muscle stiffness (rigidity) that may suggest an underlying neurologic cause of RBD, should be considered. Polysomnography
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Polysomnographic video recording is the single most important diagnostic test in persons with RBD. This test is usually conducted in a sleep study center. The person undergoing testing is required to sleep at the center while the following parameters are monitored:
Electrical activity of the brain (electroencephalogram, or EEG)
These parameters are monitored as the person passes through the various sleep stages. Characteristic patterns from the electrodes are recorded while the person is awake and during sleep. Continuous video recording is done to observe behaviors during sleep.
In persons with RBD, the polysomnogram shows an increase in the muscle tone associated with the EEG pattern of REM sleep, whereas in healthy persons, the EEG pattern of REM sleep is associated with an absence of muscle tone (atonia).
Additionally, the video recording will show body movements coinciding with the EEG pattern of REM sleep.
Imaging studies (for example, a CT scan and MRI of the brain) are not routinely indicated in persons who have no neurologic cause of RBD, but they may be done if some abnormality is detected during the neurologic exam. Imaging studies should also be considered in younger patients (younger than age 40) where there is no known precipitant cause such as alcohol or medication use.
WebMD Medical Reference
Richard Senelick, MD on October 16, 2015