Diagnosing Rem Sleep Behavior Disorder: A Comprehensive Guide

REM sleep behaviour disorder (RBD) is a rare sleep disorder that causes people to act out their dreams. Diagnosis of RBD requires a clinical history of sleep-related complex motor behaviours or REM sleep complex vocal or motor behaviours recorded during polysomnography, accompanied by REM sleep without atonia (RSWA). The polysomnographic video recording is the single most important diagnostic test for RBD. This test is usually conducted in a sleep study centre, where the person undergoing testing is required to sleep while several parameters are monitored, including the electrical activity of the brain, heart, and muscles, eye movements, and respiratory movements.

A polysomnographic video recording is the most important diagnostic test

• Electrical activity of the brain (electroencephalogram, or EEG)
• Electrical activity of the heart (electrocardiogram, or ECG)
• Movements of the muscles (electromyogram)
• Eye movements (electrooculogram)
• Respiratory movements

These parameters are monitored as the person passes through the various sleep stages, and continuous video recording is done to observe behaviors during sleep.

The polysomnographic video recording is crucial because it provides a comprehensive view of the individual's sleep patterns and behaviors. It allows for the observation of any abnormal movements or behaviors that may occur during REM sleep, which is characteristic of RBD. The video recording also helps to identify the absence of muscle tone (atonia) during REM sleep, which is a typical finding in healthy individuals.

Additionally, the polysomnographic video recording can reveal the presence of underlying neurological conditions, such as Parkinson's disease, which may be associated with RBD. The test can also help differentiate between RBD and other sleep disorders or medical conditions that may present similar symptoms.

Overall, the polysomnographic video recording is a vital tool in the diagnosis of RBD, as it provides both quantitative and qualitative data that can be analyzed by sleep specialists to make an accurate diagnosis.

The test monitors brain, heart, muscle, eye and respiratory movements

To diagnose REM sleep behaviour disorder, a test is required to monitor brain, heart, muscle, eye, and respiratory movements. This test usually takes place in a sleep laboratory, where a polysomnogram is performed.

Brain Activity

The brain is monitored using an electroencephalogram (EEG), which records electrical activity in the brain via electrodes attached to the scalp. During REM sleep, the EEG will show fast, low amplitude, desynchronized neural oscillation (brainwaves) that resemble the pattern seen during wakefulness.

Heart Activity

Monitoring heart activity during sleep can be done through wearable devices, such as smartwatches, or through medical sleep studies. During REM sleep, the heart rate may speed up to a rate similar to that of a waking heart rate.

Muscle Activity

Muscle activity can be monitored through electromyography (EMG), which records electrical activity in muscles. During REM sleep, the body experiences REM atonia, an almost complete paralysis of the body, achieved through the inhibition of motor neurons.

Eye Movements

Eye movements can be tracked through electrooculography (EOG), which records eye movements by measuring the difference in electrical charge between the front and back of the eye. During REM sleep, the eyes exhibit rapid, random movements.

Respiratory Movements

Respiratory rate is typically measured by counting the number of breaths a person takes per minute. During sleep, the respiratory rate tends to slow down, but during REM sleep, breathing becomes faster and more erratic.

Overall, the test for REM sleep behaviour disorder involves monitoring various physiological parameters, including brain, heart, muscle, eye, and respiratory activity, to understand the underlying causes of the disorder.

Imaging studies are not routinely indicated unless a neurologic cause is detected

When diagnosing REM sleep behaviour disorder (RBD), a neurologic exam is typically carried out. While this exam often presents as normal, signs and symptoms of Parkinson's disease, such as hand tremors, slowness in movement, and muscle stiffness, may indicate an underlying neurologic cause of RBD.

The single most important diagnostic test for RBD is polysomnographic video recording, which is usually conducted in a sleep study centre. This test monitors various parameters, including the electrical activity of the brain, heart, and muscles, eye movements, and respiratory movements.

Imaging studies, such as CT scans and MRIs of the brain, are not routinely indicated for RBD patients with no neurologic cause. However, they may be performed if abnormalities are detected during the neurologic exam or in younger patients (under 40) with no known cause, such as alcohol or medication use.

MRI has been suggested as a tool to understand the brain bases of isolated RBD and its evolution. Some studies have found that patients with isolated RBD have structural changes in deep gray matter nuclei, cortical gray matter atrophy, and disrupted functional connectivity within certain brain regions. These changes may be associated with the motor and non-motor symptoms of RBD.

In summary, while imaging studies are not always necessary for diagnosing RBD, they can provide valuable information about the underlying brain changes that may be contributing to the disorder.

A neurological exam is often normal, but signs of Parkinson's disease may be present

When diagnosing REM sleep behavior disorder, or RBD, a neurological exam will often appear normal. However, it is important to be vigilant for any signs of Parkinson's disease, which may be underlying RBD. Parkinson's disease is a progressive neurological disorder that causes a loss of dopamine, resulting in movement disorders.

There are four main symptoms of Parkinson's disease that a doctor will look for during a motor exam: tremors, rigidity, bradykinesia or akinesia, and postural instability. Tremors are repetitive and involuntary contractions of muscles, often affecting the mouth, hands, legs, and feet. They are usually asymmetric and present at rest, sometimes described as 'pill-rolling'. Tremors can be exacerbated by closing the eyes and counting, or by touching the finger to the nose. Rigidity refers to stiffness in the arms and legs, often initially seen on only one side of the body. It is not dependent on the speed of movement and can be tested for by passively moving the patient's limbs and checking for resistance.

Bradykinesia refers to slowness in movement, while akinesia is a lack of movement during regular tasks. A person with these symptoms may move more slowly or perform smaller movements, such as during handwriting, which may appear small and cramped (micrographia). They may also struggle with rapid, coordinated movements like clapping, pinching, or tapping. Postural instability and balance issues are also common in Parkinson's disease. The 'pull test' or 'retropulsion test' is used to assess this, where the patient is pulled back slightly to observe their reaction.

In addition to these four main symptoms, there are other clinical features of Parkinson's disease that may be observed. This includes reduced spontaneous movements and hand gestures, less frequent blinking, a lack of facial expression (hypomimia), soft and indistinct speech (hypophonia), and an abnormal, stooped posture.

RBD is diagnosed by a clinical history of dream enactment and complex motor behaviours during REM sleep

REM sleep behaviour disorder (RBD) is a parasomnia characterised by the pathological expression of overt and often violent motor behaviours during REM sleep. Those with RBD physically act out their dreams, sometimes violently, and can cause injury to themselves or their bed partner.

The video recording will also show body movements coinciding with the EEG pattern of REM sleep. This is because, in RBD, the normal muscle atonia associated with the REM stage of sleep is absent. Instead, there is an increase in muscle tone, and the person acts out their dreams.

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