**1. Introduction**

In 1969, while introducing the electroencephalographic (EEG) recordings of sleep stages, Barbara Long [1] wrote, "We know that patients in hospitals, away from their usual sleeping environments and beset by the problems created by illness, frequently have difficulty meeting one of their most basic physiologic needs—the need for sleep—at a time when they require it most." In this commentary, Long briefly introduced insomnia as one of the health problems suffered by hospitalized patients. Subsequent reports by Williams [2] and Walsleben [3] passingly mentioned other sleep disorders, but failed to elaborate on somnambulism (in the lay term, sleepwalking).

In one of the anonymous early reports [4] that appeared on somnambulism in 1834, the recommendation offered for treating somnambulism was "*to seize the arms suddenly, and halloo in the ears until the sleep awake: of the application of a jug of cold water, by pouring it suddenly upon the head. In this latter case, however, care should be taken to have the body well rubbed with dry towels after the operation.*" Whether somnambulism will be permanently cured by this sort of crude treatment is open to doubt.

Nevertheless, medical knowledge on somnambulism, especially after the discovery of rapid eye movement (REM) sleep in 1953 [5] and the use of polysomnographic detection methods [6, 7], has accumulated in the past 65 years. Though it was widely believed until 1956, that somnambulism occurs during the dream phase (i.e., REM sleep stage), Jacobson et al. [8] demonstrated in nine subjects (seven men and two women, aged 9–23 years) that somnambulistic episodes occur during the N3 stage of slow-wave sleep (SWS) or non-rapid eye movement sleep (non-REM sleep). Specific electroencephalogram features of the N3 stage of SWS include delta waves (0.5–2 Hz, amplitude >75 μV) and slow oscillations (<1 Hz) [9]. For what is known about somnambulism until now, five reviews [9–13], with over 50 citations can be consulted profitably.

The objective of this chapter is to review recent developments on the presumed etiology, associated disorders, and treatment strategies currently available for somnambulism. The interdisciplinary relevance of somnambulism between medicine and law is also highlighted.
