Evaluation of daytime sleepiness.

In summary, the evaluation of the tired patient requires an awareness of the various meanings of tiredness. Furthermore, it is important to differentiate normal sleepiness that is a product of circadian rhythm variation in vigilance from pathologic sleepiness. Sleepiness that results from faulty habits, e.g., altered sleep scheduling, drugs, or sleep restriction, can be readily discerned with the aid of a sleep-wake diary. Because subjective sleepiness is often unappreciated, especially in patients with sleep apnea, methods that rely on self-ratings of the severity of sleepiness, e.g., visual analogue scale, 10-cm line, or SSS may not coincide with performance tasks, observer assessments, or such physiologic methods as the MSLT. Less commonly employed neurophysiologic methods include pupillometry and averaged evoked potentials. On the other hand, the MSLT is commonly used for the detection of physiologic sleepiness. Moreover, it is helpful in evaluating response to treatment. A variation of the MSLT, the MWT, which instructs the individual to remain awake, does not discriminate between sleep onset times for wakefulness and the MSLT for sleepiness in normal subjects. The MWT may be useful for the assessment of treatment responses for excessive daytime sleepiness, e.g., narcolepsy, and for determining the frequency of daytime sleep episodes. The differences that have been observed between behavioral measures and physiologic measures of sleepiness suggest that these techniques assess different aspects of sleepiness. HLA typing (DR2, DQw1) has been shown to be a useful method for corroborating narcolepsy-cataplexy, but the antigens are neither specific for the disorder nor for sleepiness alone.