National Sleep Foundation

Glossary

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Parasomnias - Abnormal activities that can occur during sleep, other than sleep apnea. These activities include sleep-related abnormal movements, behaviors, emotions, and perceptions as well as dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. Parasomnias include eating disorders, sleepwalking, nightmares, sleep paralysis, REM sleep behavior disorder, and sleep aggression.

Periodic Breathing - A crescendo-decrescendo pattern of respiration, as seen in Cheyne-Stokes and high-altitude breathing, and in premature infants.

Periodic Limb Movement Disorder (PLMD) - A sleep disorder involving repetitive movements of the limb (i.e., arms, legs) that occurs during sleep, and resulting in excessive daytime sleepiness and fatigue.

Periodic limb movements during sleep (PLMS) - Body movements that occur during sleep, usually involving the person’s legs. PLMS are normal and do not cause negative effects.

Periodic Limb Movements Index - A tool used to assess the number of Periodic Limb Movements per hour of sleep, in order to assess a patient for Periodic Limb Movement Disorder (PLMD).

Polysomnography (PSG) - A diagnostic test that monitors a number of physiologic variables during both sleep and wakefulness. The test requires the patient to sleep in the lab overnight, where his/her sleep behavior is monitored by a technician and recorded on video.

Positive Airway Pressure (PAP) - First-line therapy for patients with moderate or severe obstructive sleep apnea. OSAS, the device delivers pressurized air to the upper airway (via a nasal mask, full-face mask, or nasal pillow), which prevents the upper airway from collapsing during sleep. Devices include Continuous Positive Airway Pressure (CPAP) devices, Bilevel Positive Airway Pressure (BPAP) devices, and Autotitrating Positive Airway Pressure (APAP) devices.

Propriospinal myochonus - A parasomnia characterized by brief, involuntary jerks that occur during the transition to sleep. It can be confused with Restless Legs Syndrome or sleep starts.