Neurological

The function of MSLT and polysomnography in diagnosing narcolepsy

Multiple sleep latency tests (MSLT) and polysomnographic criteria can help, although inconspicuously, to differentiate patients on narcoleptics from patients with non-narcoleptic central hypersomnolence disorder (CDH). However, they do not differentiate between narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2), as can be seen from the study results published in Sleep Medicine.

While MSLT with Signs of Onset of Sleep with Rapid Eye Movement Periods (SOREMP) is one of the most important diagnostic criteria for narcolepsy according to the International Classification of Sleep Disorders, the sensitivity and specificity of SOREMP for narcolepsy have been questioned. The aim of the current study was to report MSLT and polysomnography findings in a large cohort of patients with CDH, including data on the frequency and temporal distribution pattern of SOREMP in MSLT during the day.

This retrospective study included clinical and electrophysiological data from 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 inorganic hypersomnia and 78 (21%) with inadequate sleep syndrome.

In NT1 and NT2 patients, the mean sleep latency (2.7 minutes and 4.0 minutes, respectively) and the mean REM latency (6.0 minutes and 7.1 minutes, respectively) on MSLT and polysomnography were compared in NT1 patients to patients with NT1 significantly shorter narcoleptic CDH.

Study researchers found SOREMP in 55 (16%) patients during polysomnography; These were more common 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 SOREMPs in MSLT, including polysomnography, for the diagnosis of narcolepsy had a sensitivity of 90% (95% CI, 83-95%), 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 a higher specificity and a positive predictive value of 100% each. The occurrence of 3 or more SOREMP in MSLT and SOREMP in polysomnography had a very high specificity and a positive predictive value (100% each), but an even lower sensitivity of 38%.

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

“[F]Frequency and temporal distribution of SOREMP in MSLT naps and PSG [polysomnography] can help to distinguish narcoleptic from non-narcoleptic patients, but not to clearly separate them. In addition to the research approaches to search for novel biomarkers, it is still important to carefully phenotype patients both clinically and electrophysiologically, ā€¯concluded the study researchers.

Disclosure: This study was supported by Jazz Pharmaceuticals. For a full list of the authors’ information, see the original reference.

reference

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

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