From the Guidelines
Yes, a polysomnogram (PSG) is required to diagnose REM sleep behavior disorder (RBD). A PSG is an overnight sleep study that records brain waves, eye movements, muscle activity, heart rhythm, and breathing patterns while a person sleeps. For RBD diagnosis, the PSG must specifically demonstrate REM sleep without atonia (abnormal muscle activity during REM sleep) along with either dream-enacting behaviors observed during the study or a history of dream-enacting behaviors reported by the patient or bed partner 1. Without this objective PSG evidence, other sleep disorders that can mimic RBD (such as obstructive sleep apnea, periodic limb movement disorder, or nocturnal seizures) cannot be ruled out. The PSG also helps exclude other causes of abnormal movements during sleep. This diagnostic requirement exists because RBD is not just about acting out dreams but specifically involves a neurological dysfunction where the normal muscle paralysis during REM sleep fails to occur. Early and accurate diagnosis is important as RBD can be an early sign of neurodegenerative disorders like Parkinson's disease or Lewy body dementia in some patients.
Some key points to consider in the diagnosis of RBD include:
- The presence of sustained muscle activity in REM sleep in the chin EMG or excessive transient muscle activity during REM in the chin or limb EMG 1
- The importance of time-synchronized video PSG audio or a characteristic clinical history in addition to polysomnographic evidence of REM without atonia or excessive transient muscle activity in REM 1
- The need to distinguish RBD from other sleep disorders that can mimic its symptoms, such as obstructive sleep apnea or periodic limb movement disorder 1
Overall, a PSG is a crucial diagnostic tool for RBD, and its use is supported by the American Academy of Sleep Medicine 1.
From the Research
Diagnosis of REM Sleep Behavioral Disorder
- A polysomnogram (PSG) is a fundamental diagnostic tool used in the evaluation of sleep disorders, including REM sleep behavioral disorder (RBD) 2, 3.
- According to the International Classification of Sleep Disorders (ICSD), diagnosis of RBD can only be definitely confirmed on the basis of polysomnography 2.
- PSG is essential in the evaluation of nocturnal hypoventilation disorders of sleep, periodic limb movements of sleep, and central nervous system hypersomnia, and is probably the only way to help differentiate among complex behaviors during sleep, especially in the setting of RBD 3.
Importance of PSG in RBD Diagnosis
- PSG is crucial in corroborating the diagnosis of RBD and identifying people who may be at risk of developing neurodegenerative disorders 3.
- The capacity to establish an early diagnostic risk of potential dementia would be of critical importance once neuroprotective agents become available 3.
- New methods for scoring electromyography (EMG) activity during REM sleep have been proposed, and cutoff values have been established to aid in the diagnosis of RBD 2.
Alternative Diagnostic Methods
- While PSG is the gold standard for diagnosing RBD, alternative methods such as home sleep apnea testing (HSAT) and consumer wearable devices are being developed and implemented due to cost and accessibility limitations 3.
- However, these alternative methods have limited validation and are not yet widely accepted as a replacement for PSG in the diagnosis of RBD 3.