Sleep Terms

• Apnea - Literally means "no breath"; the cessation of airflow at the nostrils and mouth for at least 10 seconds.
• Cataplexy – refers to sudden loss of muscle tone and loss of deep reflexes that leads to muscle weakness, paralysis, or postural collapse. Usually caused by outburst of emotion: laughter, startle, or sudden physical exercise; one of the symptoms of narcolepsy.
  
• CPAP – Continuous Positive Airway Pressure – a devise used to treat sleep apnea by sending positive airway pressure to help keep an open airway, allowing the patient to breath normally through his/her nose and airway.
  Diurnal - active and wakeful in the daytime versus active in the nighttime
  
• Electroencephalogram (EEG) - recording through the scalp of electrical potentials from the brain and the changes in these potentials. The EEG is one of the three basic variables (along with the EOG & EMG) used to score sleep stages and waking. Surface electrodes are used to record sleep in humans, recording potential differences between brain regions and a neutral reference point, or between brain regions.
  
• Electromyogram (EMG) - recording of electrical activity from the muscular system; in sleep recording, synonymous with resting muscle activity or potential. The chin EMG, along with EEG and EOG, is one of the three basic variables used to score sleep stages and waking. Surface electrodes are used to record sleep in humans, measuring activity from the submental or masseter muscles. These reflect the changes in resting muscle activity. During REM sleep the chin/cheek EMG is tonically inhibited.
  
• Electro-oculogram (EOG) - recording of voltage changes resulting from shifts in position of the eyeball-possible because each globe is a positive (anterior) and negative (posterior) dipole; along with the EEG and the EMG, one of the three basic variables used to score sleep stages and waking. Human sleep recordings utilize surface electrodes placed near the eyes to record the movement of the eyeballs. Rapid eye movements in sleep indicate a certain stage of sleep ( usually REM sleep).
  
• Excessive daytime sleepiness or somnolence (EDS) - subjective report of difficulty in staying awake, accompanied by a ready entrance into sleep when the individual is sedentary
  
• Hypersomnia – excessive, prolonged sleep
  
• Hypoxemia - abnormal lack of oxygen in the blood in the arteries.
  
• Hypopnea - shallow breathing in which the air flow in and out of the airway is less than half of normal--usually associated with oxygen desaturation
  
• Insomnia – complaint describing difficulty in sleeping
  
• Multiple sleep latency test (MSLT) - a series “nap tests” utilized in the assessment of excessive daytime sleepiness.
  
• Narcolepsy - sleep disorder characterized by excessive sleepiness, cataplexy, sleep paralysis, hypnogogic hallucinations, and an abnormal tendency to pass directly from wakefulness into REM sleep
  
• Periodic Limb Movement Disorder - also known as periodic leg movements and nocturnal myoclonus. Characterized by periodic episodes of repetitive and highly stereotyped limb movements occuring during sleep. The movements are often associated with a partial arousal or awakening; however, the patient is usually unaware of the limb movements or frequent sleep disruption. Between the episodes, the legs are still. There can be marked night-to-night variability in the number of movements or in the existence of movements.
  
• Polysomnogram (PSG) - continuous and simultaneous recording of physiological variables during sleep, i.e., EEG, EOG, EMG (the three basic stage scoring parameters), EKG, respiratory air flow, respiratory excursion, lower limb movement, and other electrophysiological variables.
  
• Restless Legs Syndrome (RLS) - sleep disorder characterized by a deep creeping, or crawling sensation in the legs that tends to occur when an individual is not moving. There is an almost irresistible urge to move the legs; the sensations are relieved by movement.
  
• Sleep efficiency (SE) - proportion of sleep in the period potentially filled by sleep--ratio of total sleep time to time in bed
  
• Sleep latency - time period measured from "lights out," or bedtime, to the beginning of sleep
  
• Sleep onset - transition from wake to sleep, normally into NREM stage 1 (but in certain conditions, such as infancy and narcolepsy, into stage REMS)
  
• Sleep-onset REM period - atypical beginning of sleep by entrance directly into stage REM
  Sleep paralysis - waking and not being able to move for a short period of time, usually occurs out of REM (dream) sleep.
  
• Sleep pattern (24 hour sleep-wake pattern) - individual's clock hour schedule of bedtimes and rise times as well as nap behavior: may also include time and duration of sleep interruptions
  
• Sleep talking - talking in sleep takes place during stage REMS, representing a motor breakthrough of dream speech, or in the course of transitory arousals from NREMS and other stages. Full consciousness is not achieved and no memory of the event remains.
  
• Sleepwalker or Sleepwalking - individual subject to somnambulism (one who walks while sleeping). Sleepwalking typically occurs in the first third of the night during deep NREM sleep (stages 3 and 4).