Multiple sleep latency test (MSLT) and polysomnography criteria may assist in distinguishing, although not clearly, patients with narcoleptic from those with non-narcoleptic central disorders of hypersomnolence (CDH); they do not, however, distinguish between narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2), according to study results published in Sleep Medicine.

While MSLT with evidence of sleep onset rapid eye movement periods (SOREMP) is one of the main diagnostic criteria for narcolepsy according to the International Classification of Sleep Disorders, the sensitivity and specificity of SOREMP for narcolepsy have been questioned. The objective of the current study was to report MSLT and polysomnography findings in a large cohort of patients with CDH, including data on frequency and temporal distribution pattern of SOREMP in MSLT during the day.

This retrospective study included clinical and electrophysiological data of 370 patients with CDH treated between 2001 and 2016. Of these, 97 (26%) patients were diagnosed with NT1, 31 (8%) with NT2, 48 (13%) with idiopathic hypersomnia, 116 (31%) with nonorganic hypersomnia, and 78 (21%) with insufficient sleep syndrome.

Among patients with NT1 and NT2, mean sleep latency (2.7 minutes and 4.0 minutes, respectively) and mean REM-latency (6.0 minutes and 7.1 minutes, respectively) in MSLT and polysomnography were significantly shorter in those with NT1 compared with patients with non-narcoleptic CDH.

Study researchers found SOREMP during polysomnography in 55 (16%) patients; these were more frequent in NT1 patients (49 patients [53%]) and NT2 patients (6 patients, 21%), while no SOREMP was registered in patients with non-narcoleptic CDH.

At least 2 SOREMP in MSLT, including polysomnography, for narcolepsy diagnosis had a sensitivity of 90% (95% CI, 83-95%), with a specificity of 95% (95% CI, 90-97%), and a positive predictive value of 91% (95% CI, 84-95%). SOREMP in polysomnography had a lower sensitivity of 45%, but higher specificity and positive predictive value of 100% each. Occurrence of 3 or more SOREMP in MSLT and SOREMP in polysomnography had a very high specificity and positive predictive value (100% each) but an even lower sensitivity of 38%.

The main limitations of the study included its retrospective design, missing data on subjective measures of sleepiness and treatment status, and lack of follow-up data.

“[F]requency and temporal distribution of SOREMP in MSLT naps and PSG [polysomnography] can help to discriminate but not clearly separate narcoleptic from non-narcoleptic patients. It remains essentially important to carefully phenotype patients clinically as well as electrophysiologically, besides research approaches to find novel biomarkers”, concluded the study researchers.

Disclosure: This study was supported by Jazz Pharmaceuticals. Please see the original reference for a full list of authors’ disclosures.

Reference

Dietmann A, Gallino C, Wenz E, Mathis J, Bassetti CLA. Multiple sleep latency test and polysomnography in patients with central disorders of hypersomnolence. Sleep Med. 2021. 79:6-10. doi:10.1016/j.sleep.2020.12.037



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