Idiopathic hypersomnia: a neurological dilemma.

Historically, there has been some confusion with wakefulness test (MWT), explore the degree (or lack) of alertness, rather than real changes in sleep the use of terms such as “narcolepsy” “excessive daytime sleepiness” and “hypersomnia” [1]. The structure and amount. But many articles on “hypersomnia” are based on analyses of these types of terms have been problematic, in part because of lack of objective methods for investigating patients’ studies. Often these data cover only one 24-h period. The Van den Hoed et al. article [3] is still, complaints, and also, because of our incomplete knowledge about the neuro-anatomical structures, we believe, the only reference where up to 5 successive days of nocturnal polysomnography and neuro-physiological and biochemical factors involved in the control of sleep and wakefulness. MSLT were obtained on different types of patients complaining of daytime sleepiness. Continuous polyPatients have also contributed to the difficulties by using ambiguous terms to express their symptoms. graphic monitoring during across the 24-h period has been performed on subjects, but usually for Words such as “fatigue”, “tiredness”, “drowsiness” or “sleepiness” may all be used to express the same no longer than 48–72 h. Several methodological questions are unresolved. Is it better to monitor symptom. Patients may also fail to perceive or report their impairments. Subjective scales are availthe subject in a confined environment, continuously in bed, or is it better to allow a certain amount of able to measure symptoms, but all of these, including the Stanford Sleepiness Scale, the Karolinska scale activity, in a social environment? If the latter is and the Epworth Sleepiness Scale [2], have flaws and decided, how much activity is allowed? And what do not always reliably reflect objective sleepiness. should be the duration of the recording? In an attempt to enable more precise delineation All protocols have weaknesses, including variof separate nosologic entities, tests have been creability in degree of external stimulation, amount of ated to evaluate daytime sleepiness objectively. Polyactivity (with its potential impact on core temgraphic recording has been useful, but polygraphic perature), placement of the sleep period within the tests are limited in scope. For example, nocturnal circadian rhythm and lack of control conditions. polysomnography, due to its limited duration, is Ideally, the patient would be monitored for several more a test of biological events that occur during successive days, under normal living conditions (i.e. sleep, than an approach allowing investigation of with ambulatory monitoring methods), but such the structure of sleep. The tests that incorporate a protocol would require resolution of logistical both night and day recording, such as the multiple issues. sleep latency test (MSLT), or the maintenance of Besides the type and duration of monitoring, other methodological questions must be addressed. Which variables should be selected to study alertness and somnolence? Indices of autonomic nervous Correspondence should be addressed to: C. Guilleminault, system activity, such as pupillography? Evaluation of Stanford University Sleep Disorders Clinic, 401 Quarry Road, evoked brain responses? And if EEG analysis is Suite 3301, Stanford, CA 94305 USA. Fax: 1 650 725 8910; Email: cguil@Stanford.edu selected, how many EEG leads will be used in the