A 25 year old medical student is concerned because she has chronic daytime sleepiness. She keeps a sleep diary but sleeps exactly the same amount as classmates without chronic sleepiness. The patient is often so sleepy that she falls asleep suddenly at inappropriate times. Often when she takes notes in class, she just writes off the end of the page; she's also missed her highway exit several times. She feels most awake in the morning and right after naps.
Furthermore, just when she is falling asleep and occasionally when waking up, she has vivid frightening hallucinations. They are visual, tactile, and auditory. Immediately after awakening, she sometimes feels that she is paralyzed and cannot move for a minute or two.
Review of systems is positive for weakness only with laughing. Weird? Weird! This weakness happens mostly in the face, neck, and knees and is associated with strongly positive emotion. It lasts only a minute and does not interfere with consciousness. She does not snore and is not obese.
Challenge: What's your diagnosis?