Cataplexy - A sudden, temporary loss of muscle tone, typically triggered by a strong emotion such as surprise, laughter, or anger. Mild cases may involve only a temporary slurring of words, buckling at the knees, or the need to sit down; severe cases might result in complete postural collapse. Cataplectic episodes last from a few seconds to a few minutes and then resolve completely.
Catathrenia (Sleep-related Groaning) - A parasomnia characterized by groaning or moaning sounds, which are usually clustered and occur within a long period of expiration (2-50 seconds) subsequent to a deep inspiration.
Central Sleep Apnea (CSA) - Transient cessation of breathing (less than 10 seconds) during sleep caused by a disturbance in the brain's respiratory centers or in the respiratory feedback to these centers. With central sleep apnea (unlike with obstructive sleep apnea), there is no effort to breathe during the period of airflow cessation.
Cheyne Stokes breathing - A breathing rhythm with a specified crescendo and descrescendo change in breathing amplitude.
Circadian Rhythm - Typically emerges two to six months after birth and is entrained by light to Earth’s daily rotation (i.e., adjusted to a 24-hour cycle). Along with homeostatic influences, the circadian rhythm helps regulate sleep and wakefulness over a 24-hour period.
Circadian Rhythm Disorders - Disorders that involve problems with an individual’s internal clock that disrupt his or her sleep patterns. Shift work disorder (SWD), is a form of Circadian Rhythm Disorder.
Cognitive Behavior Therapy (CBT) - A type of therapy that involves focusing on the relationship between a person’s thoughts, feelings, and actions; often used as part of treatment for sleep disorders such as insomnia. Effective CBT treatment modalities include cognitive therapy, stimulus control therapy, sleep restriction therapy, and relaxation therapy.
Confusional arousals - A type of NREM Sleep Arousal Disorder that occurs when a person wakes up in a confused state.
Continuous Positive Airway Pressure (CPAP) - A treatment modality for sleep-related breathing disorders in which a mask (applied either to the nose or to nose and mouth) is used to open the upper airway by delivering a constant elevated air pressure to the upper airway.