BACKGROUND
Narcolepsy type 1 (NT1) is characterized by excessive daytime sleepiness, cataplexy, and cerebrospinal fluid (CSF) hypocretin-1 deficiency. Although typically occurring in younger individuals, late-onset NT1 can present with diagnostic challenges, particularly when symptoms overlap with psychiatric, neurological, or sleep-related disorders.
CASE REPORT
We report a case of a 60-year-old man with recurrent emotion-triggered muscle weakness and progressive excessive daytime sleepiness. The patient had been treated for 6 years under a diagnosis of dissociative (conversion) disorder. The weakness episodes were clinically compatible with cataplexy, as they were emotion-triggered and occurred with preserved awareness. Two polysomnography and multiple sleep latency testing evaluations demonstrated pathological sleepiness but did not meet the conventional sleep-onset rapid eye movement period (SOREMP) criterion for narcolepsy. Interpretation was complicated by moderate-to-severe obstructive sleep apnea, fragmented sleep, previous psychotropic medication exposure, and cerebral ischemic changes. CSF hypocretin-1 concentration was markedly reduced (12.08 pg/mL), confirming the diagnosis of NT1. Treatment with clomipramine and pitolisant improved daytime sleepiness and cataplexy-like episodes, with the Epworth Sleepiness Scale score decreasing from 24 at admission to 9 after 4 months of follow-up.
CONCLUSIONS
Late-onset NT1 should be considered in older adults presenting with progressive excessive daytime sleepiness and emotion-triggered weakness, even when conventional sleep studies are inconclusive. CSF hypocretin-1 measurement can provide important diagnostic evidence, while atypical neurological manifestations should be evaluated separately for alternative or coexisting disorders.

Keywords: Cataplexy; Narcolepsy