New manuscript out of the journal Nature Communications. In addition to the loss of orexin/hypocretin neurons, the authors point to another neuronal group that is degraded.
From the abstract: "...individuals having narcolepsy with cataplexy also have an average 46% loss in the number and an 18% increase in the size of brainstem norepinephrine neurons in the locus coeruleus (LC), based on our analysis of 11 brains of individuals having narcolepsy with cataplexy. Microglial clustering around Hcrt neurons in the hypothalamus and around noradrenergic neurons in the locus coeruleus of individuals having narcolepsy with cataplexy indicates microglial involvement in the degeneration of both of these neuronal groups"
PDF of full article is available via the link.