ANSWER. Typical sleep labs perform three types of tests...
Polysomnogram (PSG). You sleep overnight in the lab. Eighteen or more electrodes connect you to a computer. (A little Frankensteinian.) Sleep center technicians monitor your brain waves, eye movements, heartbeat, breathing and peripheral nervous response. The technicians also watch you on
an infrared video monitor. Afterward, a neurologist analyzes your “chart,” some 500
pages of electroencephalograph (EEG) traces. The chart also includes electrocardiogram (EKG) and other
traces. Unfortunately, sleep under lab conditions is hardly natural. To counteract this disadvantage, recently
built sleep labs look like hotel rooms. The center encourages you to pack your favorite pajamas and pillow. A
child may bring her teddy bear. Some sleep labs go a step further. They actually send technicians to the
patient's home. The technicians set up remote PSG equipment and leave. Then the patient sleeps in his own bed. The equipment sends his chart over the Internet.
MSLT. The multiple sleep latency test or MSLT is a mini-polysomnogram for 20 minutes or so
every hour. Talk about unnatural! The test checks the rapidity of falling asleep.
MWT (Maintenance of Wakefulness Test). The opposite of the MSLT. The test
checks how well you stay awake.
Beware. You might be misdiagnosing yourself. Excessive daytime sleepiness,
even with sleep paralysis, doesn't prove narcolepsy. Normal people experience microsleeps, sleep
paralysis and occasional hypnagogic or hypnopomptic dreams. Please consider the possibility of a deficiency in B1 or B-vitamin complex. Women particularly should look into a possible underactive thyroid,
or an iron deficiency. If you have fatigue, definitely ask a doctor to examine the problem. Some fatiguing
conditions such as sleep apnea, emphysema, and leukemia can be fatal.
HLA (Human Leucocyte Antigen) Marker Test. This test can confirm that you're susceptible to the
immune disease that causes narcolepsy. If the
HLA-DQB1*0602 allele is present in your blood, you have a susceptible immune system. Note that the test
isn't conclusive for narcolepsy. Many normal people have this type of immune system. Yet
the test proves that under certain conditions, your immune system might attack your hypothalamus.
Afterward, you might present classic narcolepsy. Narcoleptics without cataplexy might have a different
type of immune system.
Orexin-A / Hypocretin-1 Level Test. Non-trivial, because it requires a spinal tap. The
spinal tap (lumbar puncture) resembles an epidural injection, except the technician extracts
cerebrospinal fluid. There is risk for complications, such as severe headaches. The sleep center tests
the extract for the presence of orexin-A or hypocretin-1. (These are different names for the same
neurotransmitter.) Without this neurotransmitter, you probably have narcolepsy.
Please understand that the patient can't select tests in à la carte fashion. You neurologist will specify certain tests before he or she can render a diagnosis.
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