Idiopathic Hypersomnia
October 1, 1997 3 minutes read
Source: Bassetti C, Aldrich MS. Idiopathic hypersomnia; A series of 42 patients. Brain 1997;120:1423-1435.
Idiopathic hypersomnia is a rare disorder identified by chronic, excessive, and irresistible nocturnal and day-time sleep patterns in persons lacking an excess frequency of narcolepsy- related leukocyte antigens. Roth (Narcolepsy and Hypersomnia; 1980) first characterized and uncovered the syndrome. Bassetti and Aldrich now describe the findings of 42 such patients. During the past 10 years, their sleep center has studied a total of 63 patients considered to have the syndrome compared to 258 suffering from classic narcolepsy during the same time. Of the total with hypersomniac syndrome, 42 persons were considered to have a valid diagnosis for that disease, and 28 were available for detailed follow-up characterization. Typical characteristics were onsets between ages 6 and 43 years, driving problems, work problems, and excessive nocturnal sleeping hours plus daytime naps. Fourteen persons had naps lasting longer than 30 minutes; 22 found naps non-refreshing; headache and other functional and/or psychiatric discomforts affected more than half the subjects; and onset of sleep latency was abnormally rapid. Polysomnography on all these patients was, by definition, normal (defined below).
Bassetti and Aldrich categorize their hypersomniacs into three categories. 1) Classic idiopathic hypersomnia (n = 8) includes ". . . excessive daytime sleepiness plus nocturnal sleepiness and sleep episodes that are usually resistible, long-lasting, not refreshing and not associated with frequent periods of REM at the sleep onset. They are sometimes associated with increased total sleep, difficult awakening, and sleep drunkenness." 2) Narcoleptic-like idiopathic hypersomnia (n = 9) includes overwhelming excessive daytime sleepiness and relatively normal nocturnal sleep but lacks the classic narcoleptic leukocyte antigens. 3) Mixed idiopathic hypersomnia (n = 11) has symptoms partly similar to each of the above two groups.
The cause of idiopathic hypersomnia is uncertain. Four patients who developed hypersomnia following a sustained viral illness spontaneously improved during the following months or a year. Among the eight patients with classic hypersomnia, seven had a family history of diabetes mellitus, suggesting the possibility of a genetic autoimmune factor. Seven had fluctuations of mood, other psychiatric problems, and increased hypersomnia during the dark winter, again hinting at genetic immune abnormalities. Given their experience, the authors indicated the frequency of idiopathic hypersomnia at approximately 12-16% of the incidence of narcolepsy with an overall population prevalence of the disorder of 2-5/100,000 Caucasians.
Treatment with stimulants was prevalent and often improved outcome. Among "classic" hypersomniacs, three of five improved with amphetamine or methyl-phenidate; all seven patients with narcoleptic-like hypersomnia improved with stimulants, and five of nine with mixed idiopathic hypersomnia also improved.
COMMENTARY
The above summary of idiopathic hypersomnia nicely describes three different clinical disorders of sleep, none of which has surrendered to scientific explanations of their existence. Fortunately, many patients can find in amphetamines and methylphenidate at least moderate relief from their symptoms. A new, potentially helpful central adrenergic drug, modafinil, has now been under study for narcolepsy for several years but has not yet reached approval as a prescription drug. In this setting, Broughton et al report the relatively successful results of a double-blind, placebo-controlled, crossover trial of modafinil as a treatment for excessive daytime sleep in 75 narcoleptics (Neurology 1997;49:444-451). fp
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