My daughter has sudden periods when she just falls asleep, no matter what she is doing, it may be only momentary, but dangerous. I checked her blood sugar — 60, blood pressure — 176/91, pulse — 101. She recently had trouble driving home for lunch and almost drove off the road. Can you give me a hint?
Frequent daytime sleepiness such as you describe is often called excessive daytime somnolence (EDS). Probably the most common cause is chronic sleep deprivation, but it may be a symptom of narcolepsy — an uncommon and poorly understood syndrome. I very much doubt that your daughter’s rather low blood sugar has anything to do with this uncontrollable sleepiness. Although people can lose consciousness when the blood sugar falls very low, around — 40mg/dl, other symptoms such as nervousness, tremor, sweating, hunger, dizziness and headache will proceed loss of consciousness.
A truly hypoglycemic person who loses consciousness will not describe it as falling asleep, and it would not be momentary, as you describe happening to you daughter. Also her high blood pressure was probably a temporary response to almost driving off the road rather than something causing the EDS.
Narcolepsy consists of EDS with involuntary sleep episodes. Disturbed sleep at night is associated in 87 percent of people, and cataplexy (sudden weakness without loss of consciousness brought on by emotion) is seen in 76 percent of people with narcolepsy. Other associated symptoms are hypnogogic hallucinations (vivid hallucinatory dreams when falling asleep), and sleep paralysis (an awareness that one’s muscles are paralyzed when one is falling asleep). — Harrison’s Principles of Internal Medicine.
There appears to be a genetic component to the condition, since virtually 100 percent of people with it have a particular antigen called DR15 on their white blood cells, an antigen seen in about 25 percent of the population. Not all people carrying the antigen get narcolepsy though, since the prevalence of the condition seems to be about one in 4,000 in the U.S. First degree relatives of someone with the condition have about a one percent chance of getting it themselves, obviously much higher than the rate in the general population.
Onset is usually between 15 and 25 years-old. Initially only the sleep attacks may be present. Ultimately most narcoleptics develop cataplexy, but its manifestations may vary greatly, from one attack per year to several attacks per day. The intensity of the cataplectic attack can vary from a little jaw weakness that allows the mouth to drop open, to a complete loss of strength in all the voluntary muscles causing the person to fall to the ground.
Sleep studies are often conducted to make a definite diagnosis. During the sleep study, the person is wired up to an electroencephalogram so an (EEG) can be recorded. Sensors are placed on the eyes to record rapid eye movements (REM). Every normally sleeping person has periodic phases of REM sleep, typically occurring every 60 to 90 minutes. Someone with narcolepsy will often go into REM sleep almost immediately after falling asleep.
The sleep study may be followed by a multiple sleep latency test (MSLT), in which the patient is asked to lie down comfortably several times during the day while the time they take to fall asleep is recorded. On average, someone with narcolepsy will fall asleep much more rapidly during the day than someone without it.
Narcolepsy can pose real dangers, particularly when one is driving. Treatment is therefore usually advised, and consists basically of stimulants such as methyphenidate (Ritalin), amphetamines, modafinil (Provigil), and others. The cataplexy, hypnogogic hallucinations and sleep paralysis may respond to some antidepressants. Taking short daytime naps is also helpful. The condition usually gets better as one ages.