#Low hypocretin symptoms plus

#Low hypocretin symptoms plus

In the ICSD-3, Na-2 is defined by chronic sleepiness plus a positive MSLT as defined above. In contrast, the diagnosis of Na-2 remains challenging. 1 A thoughtful approach usually leads to high diagnostic certainty in Na-1 patients.

Usually, the diagnosis of Na-1 is straightforward as definite cataplexy can often be elicited by a careful history and low hypocretin levels are highly specific for narcolepsy. This new definition is much like that of the ICSD-2 except that low CSF hypocretin plays a more important role in the diagnosis of Na-1, and the counting/analysis of SOREMPs can now include a SOREMP within 15 minutes of sleep onset on the preceding nocturnal polysomnogram (PSG). Hypocretin deficiency is defined as cerebrospinal fluid (CSF) hypocretin-1 level < 1/3 of normal or ≤ 110 pg/mL if a Stanford reference sample is used for radioimmunoassay. A MSLT is considered positive if the mean sleep latency is ≤ 8 minutes and there are 2 or more sleep onset REM periods (SOREMP). In the ICSD-3, Na-1 is defined as excessive daytime sleepiness (EDS) and at least one of the following criteria: (a) cataplexy and a positive MSLT, or (b) hypocretin deficiency. Na-1 includes Narcolepsy with Cataplexy, and Na-2 is simply Narcolepsy without Cataplexy. In this paper, we use the new terms Narcolepsy type 1 (Na-1) and Narcolepsy type 2 (Na-2) in keeping with the revised nomenclature of the 3 rd Edition of the International Classification of Sleep Disorders (ICSD-3).

The goals of this paper are to review briefly what is known about Narcolepsy without Cataplexy, to discuss the usefulness and limitations of current diagnostic tools, and to suggest directions for research that should lead to a better understanding and more accurate diagnosis of Narcolepsy without Cataplexy. This meeting helped clarify aspects of this disorder and inspired us to write this manuscript. The participants have all published extensively on narcolepsy, and the meeting (but not the writing of this paper) was funded by Jazz Pharmaceuticals. To advance understanding of Narcolepsy without Cataplexy, a group of clinician scientists experienced in narcolepsy convened in June 2012 to discuss these diagnostic challenges. The problem is further compounded by the fact that in some patients, narcolepsy may evolve over time for example, patients in whom daytime sleepiness is the sole initial manifestation may develop cataplexy many years later. This uncertainty arises from the nonspecific nature of the symptoms, the limitations of our current diagnostic tests, and the lack of useful biomarkers. In contrast, Narcolepsy without Cataplexy is often a challenging diagnosis, even for highly experienced clinicians. Narcolepsy with Cataplexy is usually easy to diagnose as cataplexy is often distinctive and occurs in almost no other conditions.