Assessment of sleep disorders with special attention to Prader-Willi syndrome

Carol L. Rosen, M.D.

Associate Professor of Pediatrics, Pulmonology Division, Case Western Reserve University/University Hospitals of Cleveland and Director, Sleep Center, University Hospitals of Cleveland

Summary by Shawn E. McCandless, M.D.

            Sleep is a mandatory part of life, and good sleep is important to maintaining good health.   Using monitors of brain, muscle and eye activity, scientists have identified 5 major stages of the sleep cycle.  Each cycle lasts 90 – 120 minutes, so there are multiple sleep cycles per night. The rapid eye movement (REM) stage is associated with dreams and with paralysis of the muscles.  This is the sleep that is maximally restorative, but only accounts for 25% of the sleep cycle.  REM becomes longer and more frequent toward the morning.  Stages I – IV are progressively deeper stages of sleep.  A variety of parts of the brain are involved in the regulation of our sleep-wake cycle and our “internal clock” (circadian rhythm).

            A variety of biological and external factors impact our circadian rhythm, including genetic traits, brain developmental abnormalities, physiologic function, mood, light, social activity, and others.  Several important hormones involved in sleep are melatonin, which peaks during sleep hours, and cortisol, which is low during sleep hours.  Growth hormone secretion peaks during sleep.  Patterns and characteristics of sleep develop and grow over time, so sleep needs are different at different ages.

            The study of sleep involves a variety of non-invasive, but not necessarily comfortable, monitors, including monitors of EEG, muscle activity, blood oxygen, airflow and nasal pressure, heart function, and expired CO₂.  This process, called polysomnography, is best performed by child-friendly, experienced, technicians.  It takes about 1 hour to apply the sensors.  Monitors that attach to the face and nose are the most difficult for children to tolerate.  The PSG measures and correlates sleep stage, arousals from sleep, oxygen, expired CO2, and other other factors, which are then interpreted by a professional to determine the presence and extent of sleep disordered breathing, which may include obstructive apnea, hypopnea (inadequate breathing), and central apnea.

            A variety of risk factors for sleep disordered breathing may be present in children and adults with PWS, including decreased muscle tone, brain developmental abnormalities, differences in arousal to low oxygen and high CO₂, and obesity.  Other factors not related directly to PWS include enlargement of tonsils and adenoids and acute respiratory infections.  The effects of sleep apnea in childhood can include excessive daytime sleepiness, bed-wetting, growth impairment, behavioral problems, high blood pressure and heart failure.  In some ways, people with PWS may appear to have a pattern of findings similar to people with narcolepsy, including sleep onset REM periods.  Individuals with snoring, restless sleep, episodes of not breathing during sleep, bed-wetting that starts after they have been previously dry, morning headaches or excessive daytime sleepiness should have an evaluation of sleep.  Likewise, it is recommended that children with PWS have a sleep study before, and 6 to 8 weeks after, starting recombinant human growth hormone therapy.

            Treatment of sleep disordered breathing involves reducing airway obstruction by removing redundant tonsillar and adenoidal tissue, or by using an external device to keep the airway open, such a continuous positive airway pressure machine.  This machine is often not tolerated well by children.  Weight loss is also an important treatment.  If nothing else works, tracheotomy (placement of a permanent breathing tube into the trachea through the neck) may be needed.  More work is needed to understand the full spectrum of sleep problems associated with PWS, and to evaluate treatment strategies.

June 2004