The multiple sleep latency test (MSLT) is an objective measure of a patient's sleepiness and is performed to evaluate the severity of daytime sleepiness, to diagnose narcolepsy or falling asleep at inappropriate times, and to evaluate effectiveness of drug therapy for daytime hypersomnolence. Typically, the MSLT is administered the morning following sleep study. An alternative to this test is the maintenance of wakefulness test (MWT), which measures the ability of an individual to stay awake rather than to fall asleep. Both the MSLT and MWT are used to diagnose narcolepsy and to evaluate the effectiveness of pharmacologic interventions in the treatment of daytime hypersomnolence. Indications for these tests include falling asleep at inappropriate times, daytime hypersomnolence, suspected narcolepsy, and evaluation of drug effectiveness in treating various sleep disorders.
The MSLT includes the following tests:
EEG: At least two channels are recorded to determine sleep onset, sleep stages, and sleep offset.
EOG: To document both slow and REMs present at sleep onset and during REM sleep, respectively.
EMG: The chin EMG is used as a criterion for REM sleep.
ECG: To monitor heart rate and rhythm.
The MWT includes the following tests:
EMG: The chin EMG is used as a criterion for REM sleep.
ECG: To monitor heart rate and rhythm.
Typically, the MSLT or MWT is administered the morning following a sleep study. Following the sleep study, have the patient dress, eat (avoiding caffeine), and report back to the sleep laboratory.
Reapply the electrodes if necessary.
The first nap (for the MSLT) or first session (for the MWT) will begin 1.5-2 hours after morning awakening, with a minimum of four additional naps or sessions at 2-hour intervals throughout the day.
Terminate the nap or session after 20 minutes for the MSLT or after 20-40 minutes for the MWT. With the MSLT test, if the patient falls asleep, continue the recording for 15 minutes after sleep onset.
Instruct the patient to allow themselves to fall asleep or not to resist the urge to fall asleep for the MSLT, whereas for the MWT, instruct the patient to resist the urge to sleep or to attempt to remain awake.
Between the naps or sessions, ensure that the patient remains awake and encourage moving around.
Following the testing, disconnect all equipment and discharge the patient.
Have the technologist score the MSLT or MWT in conjunction with the PSG test results.
Follow guidelines in Chapter 1 for safe, effective, informed intratest care.
The term "nap" indicates a short intentional or unintentional episode of subjective sleep taken during habitual wakefulness, whereas the term "falling asleep" or "sleep onset" is defined objectively by EEG recordings (i.e., stage I of nREM sleep).
An average sleep onset of 6-9 minutes in the MSLT is considered a "gray area" diagnostically because these tests are done in a laboratory setting and not in the patient's home environment. Reevaluation may be necessary if the patient complains and symptoms persist.
An average sleep onset <5 minutes and two or more REM periods in the five to six naps during the MSLT is diagnostic for narcolepsy. This indicates a disturbance of the normal sleep architecture pattern, although the REM periods are not unlike nocturnal REM periods. These REM episodes, however, occur prematurely in the cycle and are termed sleep-onset REMs.
Pretest Patient Care
Explain MSLT or MWT purpose and procedure. Remind the patient not to change daily routines on the day of testing.
Reassure the patient that lead wires, monitors, and sensors will not interfere with sleep.
Record the patient's age, height, weight, and gender.
The patient should not consume alcohol or caffeinated beverages the day of the test.
Administer standard sleep questionnaires or scales (e.g., Epworth Scale, Stanford Scale) and evaluate.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Explain test outcome and possible need for follow-up testing. Modify the nursing care plan as needed.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
Caffeinated beverages can delay sleep, whereas sedatives (hypnotics) shorten sleep onset. Additionally, sleep deprivation may result in a false-positive MSLT result. During naps, environmental noise, lights, and temperature can have an adverse effect on the patient's ability to fall asleep.