Late-Onset Narcolepsy Type 1 With Inconclusive Sleep Studies: A Case Report

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 emotiontriggered 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.