To diagnose narcolepsy type 1 after a negative multiple sleep latency test: the contribution of systematic hypocretin measurement

STUDY OBJECTIVES: We evaluated the diagnostic potential of detecting narcolepsy type 1 (NT1) by systematically measuring cerebrospinal fluid hypocretin-1 (CSF-HCRT1) in patients with suspected central disorder of hypersomnolence (CDH), after the multiple sleep latency test (MSLT) was negative for narcolepsy criteria. MATERIALS AND METHODS: Consecutive untreated patients with suspected CDH were hospitalized at the Bologna Narcolepsy Center (Italy) from 2013 to 2024. They underwent a standardized protocol of 2-day continuous polysomnography (PSG), MSLT, and systematic CSF-HCRT1 measurement. Our focus was the identification of additional NT1 cases through the detection of low CSF-HCRT1 < 110 pg/mL among those with negative PSG-MSLT for narcolepsy (i.e. mean sleep latency>8 min or sleep onset REM periods-SOREMPs