Defining REM Sleep Behavioral Disorder

RBD can be diagnosed using polysomnography and clinical data, which include an increase in chin muscle tone, excessive chin or limb phasic muscle twitching, or violent behaviors

When the first recorded case of human rapid eye movement (REM) sleep behavioral disorder (RBD) presented in 1986, the polysomnographic (PSG) technologist on the night shift thought the PSG monitoring equipment was malfunctioning. At first, he did not understand how, if the patient was in Stage REM, there could be muscle movement. Normally, during REM sleep,¹ there is active paralysis or atonia of all muscles except the diaphragm and eye movement muscles² and a person is essentially immobilized. The theory as to why this occurs is thought to be nature’s way of protecting against harm that may come to sleepers or others from acting out their dreams. It is believed that the primary motor cortex is active in REM and all the brain mechanisms necessary for movement in REM sleep seem to work throughout the sleep stage. But nuclei are also working in the brain stem, which actively inhibit all of the communication from the brain to the skeletal muscles. Without them, all humans would be getting out of bed and acting out their dreams.

“RBD breaks all the scoring rules,” says Mark Mahowald, MD, medical director at Minnesota Regional Sleep Disorders Center at Hennepin County Medical Center, Minneapolis, where RBD was defined. RBD was named as a chronic behavior disorder of REM sleep and was classified as a new category of parasomnia by Carlos Schenck, MD, also at Hennepin. “State dissociation was dramatically advanced by RBD,” Mahowald says.

“It was so agonizing in the beginning to score the records of those first four or five RBD patients we studied at Hennepin, because physicians could not tell the difference between REM with muscle movement and wakefulness,” says Andrea Patterson, RPSGT, REEGT, clinical coordinator at the sleep disorders center at Hennepin.

The RBD Phenomena
In the early days of RBD definition, there were seven cases in a 1-year period at Hennepin, according to Mahowald. “We suddenly saw a high number of people who had sleep-related violent behavior, and it was for this reason that we were able to clearly identify RBD.” He added that since it was an unfamiliar malady at that time, RBD could have been missed if the laboratory had studied only one case. He added that sleep-related violent behavior could have been misdiagnosed as some other parasomnia such as nocturnal seizures or disorders of arousals (sleep terrors or sleepwalking). The publications from the studies performed at Hennepin remain some of the most referenced works in modern sleep research today. “For many years, RBD was only jokingly referred to as the ‘Minnesota Disease.’ We took a lot of flack,” Mahowald says.

Some of the earliest work in exploring the RBD phenomena was conducted in 1965 by Michel Jouvet, noted French sleep researcher. His team created lesions in portions of the brain stem in cats and observed the behavioral effects. They found that when the cats went into REM, they stood up and moved about. These cats appeared to be acting out specific behaviors such as pouncing and stalking. These behaviors are also found in humans with RBD. The animal-like behaviors portrayed by humans were reported by patients’ bedpartners and resembled those of large jungle cats, gorillas, bears, and seals.³

It was once suspected that narcoleptics were more prone to having RBD, Mahowald says. “The medications that are generally prescribed for narcolepsy (tricyclic antidepressants and selective serotonin reuptake inhibitors) are now known to induce RBD.” According to Mahowald, treatment with clonazepam without abuse or addiction issues stops the behavior of RBD. It is now simple to diagnose and gratifying to treat, he says. The benzodiazapine anticonvulsant clonazepam is the treatment of choice for RBD. Doses of 0.5 mg to 1.5 mg at bedtime are effective in controlling the inappropriate motor behaviors and dream disturbances, Mahowald says. The risk of dosage tolerance, adverse effects, or abuse has been shown to be low in long-term treatment.

First Documented Case
During the first documented case of RBD at Hennepin, the night shift technologist who discovered it reported the patient was having peculiar movements that resembled shoveling, Mahowald says. After the technologist went in to wake the patient, she reported she had a dream that she was shoveling snow.

“When the technologist reported the observations of the episode and we looked at the recording over and over, he kept insisting that the patient was awake,” Mahowald says. “We had our initial thoughts about what could have been happening with this patient, but after further investigation we started putting two and two together. The technologist’s observations were extremely important. If he had not been so observant, we would have never gone back to the record and gone over it again, thus the behavior would have been completely undetected in this case,” he says.

Patterson says that sleep technologists’ observations are critical for new definitions. “As Mary Carskadon, PhD, always says, the technicians are on the front line and see what no one else sees. There are conditions out there waiting to be discovered by night technicians,” she says. Patterson was part of the laboratory team at Hennepin when RBD was discovered and has also served for many years as the Association of Polysomnographic Technologists Education Chair.

RBD predominantly occurs4 in the sixth and seventh decade of life, although onset can occur at any age. There is a large male prominence in 85% to 90% of cases, with more than 200 documented cases to date, Mahowald says. “At the Mayo Clinic, in Rochester, approximately 100 patients who had RBD were virtually identical to our demographic and clinical history of polysomnographic findings.” In 1993, Schenck, Mahowald, and their team provided a comprehensive review of 96 patients diagnosed with RBD in their sleep laboratory. The vast majority of patients afflicted by RBD were older males with a mean age at onset of 52.4 years; however, females and children as young as 10 years old were diagnosed with RBD. Approximately 25% of their RBD patients reported sleep talking, yelling, and excessive limb twitching and jerking during sleep. A few rare cases gave histories suggestive of a familial predisposition.⁵ People typically do not remember RBD episodes, and functions of the autonomic nervous system that control breathing and heart rate seem to be unaffected by RBD events.⁶

Conclusion
The origin of RBD in half of the cases is idiopathic, whereas half are due to neurological causes.⁷ These illnesses include subarachnoid hemorrhage, dementia, Parkinson’s disease, cerebrovascular disease, multiple sclerosis, brain stem lesions, or neoplasms. A brain MRI may be indicated for a patient diagnosed with RBD to rule out an underlying structural lesion. RBD diagnosis is made using PSG and clinical data. PSG criteria include an increase of chin muscle tone, excessive chin or limb phasic muscle twitching, limb or body jerking, violent behaviors, absence of any electroencephalographic seizure pattern, or any epileptic activity during REM sleep; the PSG is otherwise completely normal. There is lack of association with any psychiatric disorder. Other sleep disorders such as sleepwalking and sleep talking can be present, but are not the cause of the behaviors.

Theresa Shumard is communications director for the Association of Polysomnographic Technologists (APT); editor of the APT’s international news magazine, The A2Zzz; and a member of Sleep Review’s Editorial Advisory Board.

References
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3. Carskadon MA. Encyclopedia of Sleep and Dreaming. New York: Macmillan; 1993.
4. Schenck CH, Bundlie SR, Ettinger MG, Mahowald MW. Chronic behavior disorders of human REM sleep: a new category of parasomnia. Sleep. 1986;9:293-308.
5. Schenck CH, Mahowald MW. A polysomnographic neurologic, psychiatric, and clinical outcome report on 70 consecutive cases with REM sleep behavior disorder (RBD): sustained clonazepam efficacy in 89.5% of 57 treated patients. Clev Clin J Med. 1990;57:S10-S24.
6. Schenck CH, Hurwitz TD, Mahowald MW. REM sleep behavior disorder: an update on a series of 96 patients and a review of the world literature. Journal of Sleep Research. 1993;2:224-231.
7. Dement WC. The Promise of Sleep. New York: Delacorte; 1999.
8. Diagnostic Classification Steering Committee, Thorpy MJ. ICSD-International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990.