For many patients, the history is sufficient to diagnose an arousal disorder; no laboratory studies are required. For example, typical episodes of sleepwalking or sleep terror that occur in children or young adults generally do not require additional evaluation. Diagnostic studies are more often needed if the history has atypical features, such as stereotyped behaviors, frequent occurrence in the second half of the night, or onset during adulthood. Definitive diagnosis with laboratory studies should also be considered for patients who have injured themselves during nocturnal episodes or describe potentially injurious behaviors.
VPSG is the preferred laboratory study, particularly for patients with episodes that occur nightly or almost nightly. It is most useful if a typical episode is recorded. An abrupt arousal from slow-wave sleep is a characteristic finding, usually associated with tachycardia. During an episode, regular, rhythmic, hy-persynchronous delta or theta activity may be seen, and high-voltage EEG slow-wave activity may occur just before the arousal that initiates the behaviors (Fig. 12.1). Even if the behaviors do not occur, the study may be helpful. For example, runs of hypersynchronous delta during arousals from slow-wave sleep are more common in persons with arousal disorders than in other individuals (Blatt et ai, 1991). In patients with a history suggestive of sleepwalking or sleep terrors, the occurrence of confusional arousals supports the presence of an arousal disorder. The EEG during a dissociative episode shows a waking pattern while REM sleep behavior disorder is associated with EEG features of REM sleep.
FIGURE 12.1 Arousal from delta nonrapid eye movement (NREM) sleep in child with a NREM arousal disorder. Note synchronous delta activity during arousal from delta NREM sleep, associated with a tonic increase in chin and leg EEG. In contrast to the EEG of an epileptic seizure, the delta activity does not evolve in amplitude or frequency. (From Malow B. A., and Aldrich, M. S. (2000). Neurological Monitoring Techniques, In Principles and Practice of Sleep Medicine, 3rd ed., M. H. Kryger, T. Roth, and W. C. Dement, eds., Philadelphia: W.B. Saunders, reproduced with permission.)
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