Dictionary

sleep, rapid eye movement See REM sleep.

sleep apnea Temporary stoppage of breathing during sleep, often resulting in daytime sleepiness. Treatment depends on the type of sleep apnea present. Sleep apnea is classified as obstructive or central. Sleep apnea that is associated with air passage obstruction may require losing excessive weight, avoiding alcohol and sedatives, sleeping on one side, medications to relieve…

sleep apnea, central Brief interruptions of breathing during sleep caused by failure of the brain to send the appropriate signals to the breathing muscles to initiate respiration. Central sleep apnea is less common than obstructive sleep apnea and can require mechanical ventilation. See also sleep apnea, obstructive.

sleep apnea, obstructive Brief interruptions of breathing during sleep caused by physical obstruction to the flow of air. The air cannot flow through the nose or mouth, although efforts to breathe are made. The basic problem may be blockage in the mouth or nose. Sleep apnea that is associated with air passage obstruction may require…

sleep disorder Any disorder that affects, disrupts, or involves sleep. The most common sleep disorder is snoring, although it is usually not medically significant. Insomnia, sleep apnea, restless legs syndrome, and sleepwalking are also sleep disorders. Many large medical centers have diagnostic and treatment facilities dedicated to diagnosing and treating sleep disorders. See also sleep…

sleepwalking Purposeful moving, usually but not always including walking, while in a deep stage of sleep. Sleepwalking occurs most frequently in children, particularly boys. Sedatives tend to exacerbate rather than cure sleepwalking. The best measures are preventive: Ensure that the sleepwalker is in a safe room for walking and cannot accidentally fall through an open…

slipped capital femoral epiphysis A condition in which the growth plate of the femur is pushed out of position, causing hip pain, stiff gait, and sometimes knee pain. Abbreviated SCFE. SCFE is most common in overweight teenagers. Treatment involves orthopedic surgery to bring the bone back into alignment.

A slipped disk is another name for a herniated disk. It occurs when the soft inner part of an intervertebral disk pushes through a crack in the tougher outer layer. This can irritate nearby nerves and cause pain, numbness, or weakness, often in the back, neck, arms, or legs. Although “slipped disk” is a common…

slow virus A virus that has a long incubation period before the onset of a very gradual progressive disease. Typically, the diseases caused by slow viruses affect the central nervous system and are associated with a variety of nervous system symptoms while having a characteristically protracted, progressive clinical course.

small for gestational age In a full-term infant, weighing 2,500 g or less at birth. Abbreviated SGA. Infants who are SGA are considered to have intrauterine growth retardation, given their gestational age. By contrast, an infant may weigh 2,500 g or less simply because of prematurity.

small-cell lung cancer An aggressive type of lung cancer in which the cancerous cells appear smaller under a microscope than those in the other common forms of lung cancer (non-small-cell lung cancer) and have a characteristic microscopic appearance. Treatment options for small cell cancer may be different than for other types of lung cancers (non-small…

smallpox A highly contagious and frequently fatal viral disease that is characterized by a biphasic fever and a distinctive skin rash that leaves pock marks in its wake. Because of its high case-fatality rates and transmissibility and because people haven’t been vaccinated against it in years, smallpox now represents a serious bioterrorist threat. The disease…