A polysomnogram is a comprehensive, all night testing procedure. Electrodes and sensors are attached to the patient’s head, chest, abdomen and legs to continuously record brain activity, various types of muscle activity, eye movements, heart rate and rhythm, breathing and oxygen saturation. A MSLT or MWT may be scheduled after the overnight sleep study. These tests use an abbreviated version of the full polysomnogram and are performed the following day. A MSLT is used to diagnose excessive sleepiness or narcolepsy during 4 or 5 nap opportunities. The MWT documents the ability to stay awake while sitting in a dimly lit room.