Sleep Evaluation and Testing
Clinical assessment
A thorough history covers sleep schedule, symptoms, bed partner observations, medications, and comorbidities. Validated instruments include the Epworth Sleepiness Scale (situational sleepiness), STOP-BANG (OSA risk), Insomnia Severity Index, and Pittsburgh Sleep Quality Index. Physical exam focuses on airway, BMI, neck circumference, and craniofacial features.
Polysomnography
PSG records EEG, EOG, EMG, airflow, respiratory effort, oximetry, ECG, and body position. Scoring per AASM rules: sleep onset is the first epoch of any sleep stage; an arousal requires an abrupt EEG frequency shift of at least 3 seconds. Apnea is a ≥90% airflow drop for ≥10 seconds; hypopnea requires a ≥30% drop with ≥3% desaturation or an arousal. The apnea-hypopnea index is events per hour of sleep.
MSLT and MWT
The MSLT (four to five naps, 2 hours apart) quantifies sleep latency and sleep-onset REM periods; mean sleep latency ≤8 minutes plus ≥2 SOREMPs supports narcolepsy. The MWT measures the ability to stay awake and is used for treatment response. Actigraphy estimates rest-activity patterns over days to weeks and is useful for circadian assessment; it cannot diagnose apnea.
Traps
Do not diagnose narcolepsy from a single SOREMP; REM in the first epoch of the night can occur in sleep deprivation or depression. A negative study while on REM-suppressing medications is unreliable. Distinguish central from obstructive events by effort signals.
Rule of thumb: Before any MSLT, confirm adequate sleep (actigraphy or diary for 1-2 weeks) and taper REM-suppressing drugs when safe; otherwise results are uninterpretable.