You are in: eMedicine Specialties > Neurology > EEG Atlas: Normal Sleep EEG - Stages III and IVArticle Last Updated: *ba 0, 0AUTHOR AND EDITOR INFORMATIONSection 1 of 6
  Author: Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital Selim R Benbadis is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association Coauthor(s): Diego Rielo, MD, Staff Physician, Department of Neurology, Memorial Hospital West, Memorial Hospital Pembroke, Memorial Healthcare Editors: Leslie Huszar, MD, Consulting Staff, Department of Neurology, Indian River Memorial Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Norberto Alvarez, MD, Assistant Professor, Department of Neurology, Harvard Medical School; Consulting Staff, Department of Neurology, Boston Children's Hospital; Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital; Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants Author and Editor Disclosure Synonyms and related keywords: delta sleep, delta waves, sleep stages, slow wave sleep, SWS, sleep stages, REM sleep, NREM sleep, rapid eye movement, nonrapid eye movement, EEG atlas, normal sleep stage III, normal sleep stage IV, sleep cycles INTRODUCTIONSection 2 of 6
  Loomis provided the earliest detailed description of various stages of sleep in the mid-1930s, and in the early 1950s Aserinsky and Kleitman identified rapid eye movement (REM) sleep. Sleep generally is divided in two broad types: nonrapid eye movement sleep (NREM) and REM sleep. On the basis of EEG changes, NREM is divided further into 4 stages (stage I, stage II, stage III, stage IV). NREM and REM occur in alternating cycles, each lasting approximately 90-100 minutes, with a total of 4-6 cycles. In general, in the healthy young adult NREM sleep accounts for 75-90% of sleep time (3-5% stage I, 50-60% stage II, and 10-20% stages III and IV). REM sleep accounts for 10-25% of sleep time. Total sleep time in the healthy young adult approximates 7.5-8 hours. In the full-term newborn, sleep cycles last approximately 60 minutes (50% NREM, 50% REM, alternating through a 3-4 h interfeeding period). The newborn sleeps approximately 16-20 hours per day; these numbers decline to a mean of 10 hours during childhood. Stages III and IV usually are grouped together as "slow wave sleep" or "delta sleep." Slow wave sleep (SWS) usually is not seen during routine EEG, which is too brief a recording. However, it is seen during prolonged (>24 h) EEG monitoring. Representative examples of SWS EEGs are shown in Images 1-2. Men aged 20-29 years spend about 21% of their total sleep in SWS, those aged 40-49 years spend about 8% in SWS, and those aged 60-69 spend about 2% in SWS (Williams et al, 1974). Notably, elderly people's sleep comprises only a small amount of deep sleep (virtually no stage IV sleep and scant stage III sleep). Their total sleep time approximates 6.5 hours. SWS is characterized by relative body immobility, although body movement artifacts may be registered on electromyogram (EMG) toward the end of SWS. Patient Education For excellent patient education resources, visit eMedicine's Procedures Center. Also, see eMedicine's patient education articles Sleep: Understanding the Basics and Electroencephalography (EEG). WAVEFORM DESCRIPTIONSSection 3 of 6
SWS, or delta sleep, is characterized, as the name implies, by delta activity. This typically is generalized and polymorphic or semirhythmic. By strict sleep staging criteria on polysomnography, SWS is defined by the presence of such delta activity for more than 20% of the time, and an amplitude criterion of at least 75 µV often is applied. The distinction between stages III and IV is only a quantitative one that has to do with the amount of delta activity. Stage III is defined by delta activity that occupies 20-50% of the time, whereas in stage IV delta activity represents greater than 50% of the time. Sleep spindles and K complexes may persist in stage III and even to some degree in stage IV, but they are not prominent. CLINICAL CORRELATIONSection 4 of 6
As mentioned above, SWS usually is not seen during routine EEG, which is too brief a recording. However, it is seen during prolonged EEG monitoring. One important clinical aspect of SWS is that certain parasomnias occur specifically out of this stage and must be differentiated from seizures. These "slow wave sleep parasomnias" include confusional arousals, night terrors (pavor nocturnus), and sleepwalking (somnambulism). MULTIMEDIASection 5 of 6
REFERENCESSection 6 of 6
EEG Atlas: Normal Sleep EEG - Stages III and IV excerpt Article Last Updated: *ba 0, 0 | ||||||||||||||
