In contrast to somnambulism in children the onset of sleepwalking or night terrors for the first time in adult life is most unusual, and occasionally suggests the presence of psychiatric disease or drug intoxication. Almost always, the adult sleepwalker has a history of sleepwalking as a child, although there may have been a period of freedom between the childhood episodes and their reemergence in the third and fourth decades. Adult somnambulism also occurs during N3 of NREM sleep, but unlike the childhood type, is not confined to the earlier part of the night. If one extends the category of somnambulism to all forms of nocturnal wandering, it seems to be remarkably common, with a lifetime prevalence of 29% of U.S. adults according to the survey by Ohayon and colleagues (2012).
Somnambulism in the adult, as in the child, can be a purely passive event unaccompanied by fear or other signs of emotion. More frequently, however, the attack is characterized by frenzied or violent behavior associated with fear and tachycardia, like that of a night terror and sometimes with self-injury. Very rarely, crimes have reportedly been committed during sleepwalking, but the authors are skeptical that organized and planned sequential activity is possible. The finding of normal sleep patterns on polysomnography distinguishes these attacks from complex partial seizures. They can be eliminated or greatly reduced by the administration of clonazepam (0.5 to 1.0 mg) at bedtime. Some patients respond better to a combination of clonazepam and phenytoin or to flurazepam (Kavey et al).
An associated but unclassifiable disorder is “night eating” in which the individual seeks out mainly carbohydrates and is only aware of their actions on the following morning when they see the mess they have left. Also, in the provocatively named “sexomnia,” the individual, male or female, engages in sexual activity, sometimes forcefully, and has no recollection of the events. The status of these syndromes as authentic parasomnias is unclear.
REM Sleep Behavior Disorder (RBD, RSBD)
This is a recognized parasomnic disorder, occurring in adult life, most commonly in older men without a history of childhood sleepwalking. It is characterized by attacks of vigorous, agitated, and often dangerous motor activity accompanied by vivid dreams (Mahowald and Schenck). The characteristic features are angry speech with shouting, violent activity with injury to self and bed mate, a very high arousal threshold, and the variable but sometimes detailed recall of a nightmare of being attacked and fighting back or attempting to flee. The episodes vary in frequency in affected individuals, occurring once every week or two or several times nightly. The episodes, which occur exclusively during REM sleep, usually in the second half of the night, are out of keeping with the patient’s waking personality. Polysomnographic recordings during these episodes have disclosed augmented muscle tone but no seizure activity.
The rare appearance of this disorder with pontine infarctions has been mentioned earlier in the chapter. However, in a series of 93 cases of REM sleep behavior disorder reported by Olson and colleagues, more than half were associated with some other neurologic disorder, in particular Parkinson disease, multiple system atrophy, and Lewy-body dementia, but in other series, with a larger variety of degenerative and other neurologic conditions. A more systemic polysomnographic examination of 457 patients with Parkinson disease by Sixel-Döring and colleagues found REM sleep behavior disorder in 46 percent. Viewed from another perspective, Postuma and coworkers have reported that one-quarter of individuals with idiopathic REM sleep disorder later developed a neurodegenerative disorder, similar to or slightly lower than other series. These observations have led to the suggestion that this disorder is an early manifestation of a degenerative brain disease characterized by the deposition of alpha-synuclein in certain neuronal systems, as summarized by Boeve and associates.