REM Sleep Behavior Disorder (cont.)

Neurologic examination

The neurologic examinationis often normal. However, symptoms and signs of Parkinson disease,such as hand tremor at rest, slowness in movement, and muscle stiffness (rigidity)that may suggestan underlying neurologic cause of REM sleep behavior disorder (RBD), should be considered.

Polysomnography

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 [EEG])
  
  
• Electrical activity of the heart (electrocardiogram [ECG])
  
  
• Movements of the muscles (electromyogram)
  
  
• Eye movements (electrooculogram)
  
  
• Respiratory movements

These parameters are monitored as the person passes through the various sleep stages. Characteristic patterns from the electrodes are recorded while the personis awake and during sleep. Continuous video recording is done toobserve 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 associatedwith an absence of muscle tone (atonia).

Additionally, the video recording shows body movements coinciding with the EEG pattern of REM sleep.

Imaging studies

Imaging studies (for example, 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 neurologic examination. 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 (see Causes).