REM sleep behavior disorder

RBD REM-sleep behavior disorder Academy of Sleep Medicine. An update on the dopaminergic... 

Sleep-wake state alterations in PD can be broadly classified into disturbances of (1) thalamocortical arousal state and (2) excessive nocturnal movement (Rye and Bliwise 2004 Rye and Iranzo 2005). The former includes the loss of sleep spindles and SWS, daytime sleepiness, and intrusion of REM sleep into daytime naps (i.e. sleep onset REM periods, or SOREMs), and the latter encompass periodic leg movements of sleep (PLMs) and REM sleep behavior disorder (RBD). The pathophysiological basis of sleepiness and SOREMs appears to be dopaminergic cell loss in PD, though excessive nocturnal movements are not as clearly related to dopaminergic deficits. 

Albin R., Koeppe R., Chervin R. et al. (2000). Decreased striatal dopaminergic innervation in REM sleep behavior disorder. Neurology. 55, 1410-12. 

Boeve B., Silber M., Pirisi J. et al. (2003). Synucleinopathy pathology and REM sleep behavior disorder plus dementia or parkinsonism. Neurology 61, 40-5. 

Gagnon J., Bedard M-A., Fantini M. et al. (2002). REM sleep behavior disorder and REM sleep without atonia in Parkinson s disease. Neurology 59, 585-9. 

Turner R., DAmato C., Chervin R., (2000). Blaivas M. The pathology of REM-sleep behavior disorder with comorbid Lewy body dementia. Neurology 55, 1730-2. 

TABLE 45-1 a-Synuclein diseases Idiopathic Parkinson s disease Dementia with Lewy bodies Pure autonomic failure REM sleep behavior disorder Lewy body dysphagia Incidental Lewy body disease Inherited Lewy body diseases Multiple system atrophy... 

That adverse consequences would arise—were it not for the active inhibition of movement—is made dramatically clear by patients who lose their innate ability to block other motor outputs and hence enact their sometimes self-injurious dream scenarios. We will come back to this story when we discuss the tendency of some legally prescribed, consciousness altering drugs to mimic those CNS degenerative diseases that cause this so-called REM sleep behavior disorder. The one motor system whose REM sleep activation results in real, not fictive movement is, of course, the one that moves the eyes rapidly, giving REM its name. There is no need to inhibit this system, because its motor output creates no behavioral disruption of sleep or other adverse consequences for the dreamer. 

To help the reader understand the reasons for this emphasis on the brain, we now turn our attention to two specific disorders of sleep and dreaming that illustrate, respectively, a genetically determined predisposition to experience dreamlike consciousness in waking (narcolepsy) and an acquired tendency to express dream behavior in sleep (REM sleep behavior disorder). The existence of these clear abnormalities emphasizes what we have learned earlier in the chapter about the normal difficulty we have in containing dreaming to consciousness within sleep. 

The REM sleep behavior disorder has carried us across the border between functional sleep disorders associated with easily reversible alterations in consciousness to structural disease of the brain associated with irreversible alterations in consciousness, leading to its ultimate loss in coma and death. Whether that border—like the border between the normal states of consciousness—is fuzzy or sharp, ragged or smooth, continuous or discontinuous, remains to be seen, but one thing is clear the border between the functional and the structural can be crossed and when it is, the states of consciousness are permanently altered. They also vividly instruct us to keep our eyes open for new and unexpected discoveries and our minds open for new and surprising concepts. 

One unexpected observation, which I will discuss in chapter 10, is that some SSRI drugs that potentiate the serotonin system in favor of enhanced mood in depression cause disturbingly long-lasting alterations in REM sleep physiology, and these alterations sometimes cross the border into the REM sleep behavior disorder. 

But later, in Phase II, after two years of continuous use, the SSRIs may contribute to a more ominous motor syndrome, the REM sleep behavior disorder described in chapter 8 as the enactment of dreamed movement. Eor reasons still not well understood, the drugs interfere with our normal ability to inhibit motor outputs. As with tardive dyskinesia victims, patients who develop SSRI-induced RBD may find that their sleep disorder does not abate when they discontinue the drug. The RBD can itself be treated with benzodiazepines—Clonazepam, for example. But that may be throwing good drug money after bad. And a more disturbing possibility, not yet observed, is that the SSRI-induced RBD will evolve in the same way that spontaneous RBD does to full-blown Parkinson s disease. 

Did you ever see a dream walking asks the popular 1940s love song, Well, I did. And so did Carlos Schenck and Mark Mahowald when they recorded patients with the REM sleep behavior disorder (RBD) in their sleep lab. In chapter 8, I described the dramatic emergence in the REM sleep of some middle-aged people of motor acts that bore a 1 1 relationship to the subjective experience of dream movement. 

Now Schenck, Mahowald, and others tell us that not only does SSRI treatment potentiate eye movements in NREM sleep, but that it may also potentiate dream enactment in REM sleep. In other words, SSRIs may induce the REM sleep behavior disorder How does this work In addition to releasing the saccade generator from inhibition, the drug appears to interfere with the spinal cord inhibitory mechanism that normally blocks the central motor commands that so convincingly animate our dreams but do not result in real behavior. 

The nigrostriatal pathway connects the substantia nigra to the striatum, an area important to movement. Substantia nigra damage leads to Parkinsonism, of which the REM sleep behavior disorder is a herald. 

Further disruption of REM sleep is related to the presence of hallucinations and REM sleep behavior disorder in Parkinson s patients. A decrease in REM sleep has been associated with nocturnal hallucinations (125), and REM intrusion during daytime hallucinations has been reported (126). More than one third of Parkinson s patients also suffer from REM sleep behavior disorder (RBD) (127,128) or REM sleep without atonia (128). In these patients, there is also a significant reduction in total sleep time. In many cases RBD is diagnosed several years prior to the onset of Parkinson s disease (129), although a link between disease severity and duration and the presence of RBD has also been reported (128). RBD is most often treated with the administration of clonazepam (104,129). Patients with comorbid dementia and depression also experience a high level of sleep disturbance, associated with nocturnal vocalizations and hallucinations (130). One side effect of many antidepressant medications, however, is insomnia and sleep disturbance (131). 

Significant periods of movement are also evident during REM sleep periods, when REM sleep behavior disorder is present (117,138). These include vocalizations, increased muscle tone, and complex muscle movements. During NREM sleep, increased incidence of periodic limb movements is also evident in up to one third of Parkinson s patients (139). Muscle activity is often present in limbs that also express tremor during waking periods. 

Ferini-Strambi L, Zucconi M. REM sleep behavior disorder. Clini Neurophysiol 2000 111 S136-S140. 

Lapierre O, Montplaisir J (1992) Polysomnographic features of REM sleep behavior disorder development of a scoring method (see comments). Neurology 42 1371-1374... 

Onofij M, Luciano AL, Thomas A, Jacono D, D Andreamatteo G (2003) Mirtazapine induces REM sleep behavior disorder (RBD) in Parkinsonism. Neurology 60 113-115... 

In addition to the sleep disturbances that result from normal aging or brain disease, sleep quality may be impaired by primary sleep disorders, some of which occur with increasing prevalence with age. Sleep disordered breathing (sleep apnea), restless legs syndrome (RLS) and REM sleep behavior disorder (RBD) are three such primary sleep disorders that are more prevalent in older adults. 

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