Clinical Features Of Rapid Eye Movement Sleep Behavior Disorder

Although various PSG and clinical features of RBD have been identified by investigators from three continents since 1966 (Mahowald and Schenck, 1994), RBD was not formally recognized and named until 1986-1987 (Schenck et al., 1986; Schenck et al., 1987). RBD was incorporated within the international classification of sleep disorders (ICSD) in 1990. A typical clinical presentation of RBD is as follows (Schenck et al., 1986):

A 67-year-old dextral man was referred because of violent behavior during sleep He had slept uneventfully through adolescence in a small room with three brothers. But on his wedding night, his wife was "scared with surprise" over his sleep talking, groaning, tooth grinding, and minor body movements. This persisted without consequence for 41 years until one night, 4 years before referral, when he experienced the first 'physically moving dream' several hours after sleep onset; he found himself out of bed attempting to carry out a dream. This episode signaled the onset of an increasingly frequent and progressively severe sleep disorder; he would punch and kick his wife, fall out of bed, stagger about the room, crash into objects, and injure himself ... his wife began to sleep in another room 2 years before referral. They remain happily married, believing that these nocturnal behaviors are out of his control and discordant with his waking personality.

One example of "oneirism" (dream-enacting behavior) in this patient is as follows:

I was on a motorcycle going down the highway when another motorcyclist comes up alongside me and tries to ram me with his motorcycle. Well, I decided I'm going to kick his motorcycle away and at that point my wife woke me up and said, "What in heavens are you doing to me?" because I was kicking the hell out of her.

This same patient cited another example:

I was a halfback playing football, and after the quarterback received the ball from the center he lateraled it sideways to me and I'm supposed to go around end and cut back over tackle and—this is very vivid—as I cut back over tackle there is this big 280-pound tackle waiting, so I, according to football rules, was to give him my shoulder and bounce him out of the way, and when I came to I was standing in front of our dresser and I had knocked lamps, mirrors, and everything off the dresser, hit my head against the wall and my knee against the dresser.

This patient had sustained ecchymoses and lacerations during these recurrent nocturnal episodes.

Data on a series of 96 consecutively documented cases of RBD from one center (Schenck et al., 1993) are contained in Table 13.1. These data remain fully representative of the current series of 158 patients (Schenck and Mahowald, 1996a). Data from two other centers (Sforza et al., 1997; Olsen et al., 2000) on their series of 52 and 93 RBD patients, respectively, correspond closely to the data from our center's series of RBD patients. The older male predominance in RBD is striking, although females and virtually all age groups are represented. One quarter of the patients have a prodrome, often lengthy, involving subclinical behavioral release during (presumed REM) sleep. The frequent presence of periodic and aperiodic movements during NREM sleep suggests a strong tendency for generalized sleep motor dysregulation across REM and NREM sleep in RBD. Also, the elevated percentage of stage 3 to 4 NREM sleep in three-quarters of the patients (a finding matched in a series of 25 RBD patients from another center [Iranzo and Santamaria, 1998]) suggests an additional component of NREM sleep dysregulation in RBD. Finally, histories of childhood sleepwalking or sleep terrors are rare in RBD.

Customary cycling among REM and NREM sleep stages is usually preserved, as is the sleep architecture, apart from an elevated stage 3/4 (delta) sleep % (Schenck and Mahowald, 1990). However, a shift toward light sleep with an elevated percentage of stage 1 can occur in some cases (Schenck et al, 1987; Sforza et al, 1988). Sleep-disordered breathing is uncommon in RBD and, when present, is usually mild; it is possible that RBD may protect against obstructive sleep apnea (Schenck and Mahowald, 1992a).

All PSG and behavioral features of RBD are indistinguishable across subgroups, irrespective of gender, age, or the presence or absence of a neurological disorder (Schenck and Mahowald, 1990). This suggests the presence of a "final common pathway" in RBD that can be accessed by a wide variety of pathological states. Figures 13.1-13.3 depict a range of common PSG findings in RBD. One finding that merits particular emphasis is that loss of submental (i.e., background) electromyographic (EMG) atonia is not necessary for the release of excessive phasic EMG twitching during REM sleep, nor for the expression of RBD behaviors. Figure 13.IB illustrates this important point. Our center has also quantitatively analyzed the EMGs during REM sleep in 17 older males with idiopathic RBD and found that submental EMG atonia was preserved in 54% of all 7.5-s time bins containing bursts of phasic limb twitching (Schenck et al, 1992).

RBD behaviors occur within REM sleep, often without associated tachycardia. Complex RBD behaviors are generally aggressive or exploratory, and never appetitive (feeding, sexual). There is a very close association between altered dreams and dream-enacting behaviors, suggesting a mutual pathophysiology: patients do not enact their customary dreams, but instead they enact distinctly altered dreams, usually involving confrontation and aggression with unfamiliar people and animals.

Despite the impressive EMG motor activity and repeated behavioral release during sleep, only a small number of RBD patients complain of excessive sleep disruption and daytime fatigue, and multiple sleep latency testing rarely documents daytime somnolence (Schenck and Mahowald, 1990), apart from cases in which RBD is associated with narcolepsy.

Data on RBD from the world literature (Schenck and Mahowald, 1996a) closely match the data from our center listed in Table 13.1. Approximately half of RBD cases in the published world literature are closely associated with neurological disorders, with great diversity in category and location along the central neuraxis. Three pertinent comments are warranted: first, neurodegenerative disorders and narcolepsy are the most common neurological disorders associated with RBD. Second, the pons is rarely grossly involved, as ascertained by clinical neuroanatomical and neurophysiological testing, which stands in contrast to the animal model of RBD. Third, virtually all the neurological disorders can also manifest as "REM sleep without atonia" and/or excessive phasic EMG twitching in REM sleep, but without the clinical emergence of RBD — in other words, various subclinical forms of

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