The association between narcolepsy and REM behavior disorder (RBD).

BACKGROUND AND PURPOSE: Rapid eye movement (REM) sleep Behavior Disorder (RBD) is a movement disorder associated with loss of REM-related muscle atonia and is characterized by complex, vigorous and frequently violent dream-enacting behavior during REM sleep. RBD is usually idiopathic or secondary to neurological problems such as Parkinson's disease. This study looked at the association of RBD with another sleep disorder, narcolepsy. PATIENTS AND METHODS: Seventy-eight questionnaires were sent to known narcoleptics chosen at random from those with contact details available at the center. The questionnaire addressed current narcolepsy symptoms, medication use and symptoms of RBD. Positive questionnaire results were followed up with a telephone interview. Limited polysomnography (PSG) data was also analyzed. RESULTS: Fifty-five patients responded (response rate 71%). Of these, 20 (36%) had symptoms suggestive of RBD. The typical RBD patient is an older male (mean age of onset 60.9 years, 87% male); however, in this study, females were as likely to have RBD as males, and the mean age was 41 years. Sixty-eight percent of patients who regularly experienced cataplexy and the associated symptoms of narcolepsy (sleep paralysis, hypnogogic hallucinations and automatic behavior) had RBD, compared to 14% of those who never or rarely experienced these symptoms. CONCLUSION: This study implies a stronger relationship between these disorders than a previously published figure of 7-12% This is clinically significant as RBD is a potentially distressing but readily treatable disorder. It follows that narcoleptics, especially those with cataplexy and other associated symptoms, should be questioned about symptoms of RBD and treated accordingly. Similarly, anyone presenting with RBD should be assessed for symptoms of narcolepsy, particularly if female or of a younger age group than would otherwise be expected.

Hypocretin (orexin) deficiency in narcolepsy and primary hypersomnia.

The discovery that hypocretins are involved in narcolepsy, a disorder associated with excessive daytime sleepiness, cataplexy, and unusually rapid transitions to rapid eye movement sleep, opens a new field of investigation in the area of disorders of sleep and activation. Hypocretin-1 (hcrt-1) and hypocretin-2 (hcrt-2) (also called orexin-A and orexin-B) are newly discovered neuropeptides processed from a common precursor. Hypocretin containing cells are located exclusively in the lateral hypothalamus, with widespread projections within the central nervous system. The role of the hypocretin system in other disorders causing excessive daytime sleepiness is more uncertain. This study reports the findings of a prospective study measuring cerebrospinal fluid concentrations of hypocretin-1 and hypocretin-2 in HLA DQB1*0602 positive narcolepsy with cataplexy, monosymptomatic narcolepsy, and primary hypersomnia. The results confirmed the previous observations, that hcrt-1 is deficient in narcolepsy and for the first time report very low levels of hcrt-1 in primary hypersomnia. It is also reported for the first time that there is a generalised defect in hcrt-2 transmission in all three of these clinical entities compared with controls.