An Unusual Cause of Increasing Excessive Daytime Sleepiness in a CPAP-treated Obstructive Sleep Apnea Patient

The onset of narcolepsy type 1 (NT1) occurs after 50 years of age in less than 2% of the cases. In older adults, the diagnosis is often delayed due to the presence of neurological degenerative and inflammatory comorbidities and overlapping sleep disorders. We report the case of a 63-year-old man with a 5-year history of excessive daytime sleepiness (EDS) and a 2-year diagnosis of obstructive sleep apnea syndrome (OSAS), which. OSAS was confirmed by respiratory polygraphy that showed an apnea-hypopnea index (AHI) of 71 events/hour of sleep associated with significant nocturnal hypoxemia (lowest oxygen saturation: 53%), which lead to the initiation of continuous positive airway pressure (CPAP) treatment. Cognitive complaints, unexplained spells of dizziness, and lack of improvement in EDS with CPAP led to further diagnostic investigation of infectious, inflammatory, and neurodegenerative disorders. Low hypocretin levels in the cerebrospinal fluid (CSF) confirmed the diagnosis of NT1, and the patient's symptoms improved with the treatment with pitolisant. Though exceptional in older adults, NT1 should be suspected in the presence of atypical EDS with neurological complaints, unexplained dizzy spells, or OSAS that resists the CPAP treatment. Low levels of hypocretin in the CSF are highly specific and rule out other neurological and sleep disorders.