Unexpected REM sleep excess associated with a pontine lesion in multiple sclerosis

Status Cataplecticus with Rapid Eye Movement Sleep Excess in Late-onset Narcolepsy Type 1

A 57-year-old man presented with difficulty speaking and walking along with increased daytime somnolence. His symptoms fluctuated throughout the day but never completely disappeared. A neurological examination revealed mild dysarthria, limb weakness, and staggering gait. Polysomnography showed rapid eye movement (REM) sleep excess (55.0%). Multiple sleep latency tests revealed a mean sleep latency of zero minutes with sleep-onset REM periods in all naps. The Orexin-A concentration in the cerebrospinal fluid was low (50.8 pg/mL). Human leukocyte antigen testing demonstrated DQB1*0602 positivity. His neurological symptoms were relieved by clomipramine. Thus, he was diagnosed with late-onset narcolepsy type 1 with status cataplecticus.