ABSTRACT
Decreased cerebrospinal fluid (CSF) hypocretin-1 (hcrt-1, orexin A) was first observed in nine patients from the Netherlands with narcolepsy-cataplexy, seven of whom had undetectable hcrt-1 levels (1). Measuring CSF hcrt-1 was later shown to be highly specific and sensitive for narcolepsy-cataplexy (2-8). Rare (10-25%) subjects with narcolepsy without cataplexy and no subjects with idiopathic hypersomnia have been found to have low CSF hcrt-1 (2-8). Hcrt-1 was also measured in the CSF of patients with various neurological and sleep disorders, and levels were shown to be normal or slightly decreased in selected severe neurological disorders (3,7,9). In this chapter, we will briefly review current knowledge pertaining to the use of CSF hcrt-1 measurements in the diagnosis of narcolepsy.
