Clinical and Neurophysiological Characteristics of Narcolepsy

First reports of narcolepsy with cataplexy in Russia were made by Mankovsky in 1925 (narcolepsy with cataplexy, NC). The largest series of patients (n=110) was reported by A. Vein in 1964. Narcolepsy remains however until today relatively unknown in Russia. The aim of this study is to report clinical and polysomnographic (PSG)/multiple sleep latency test (MSLT) results in a Russian population and compare them with the European narcolepsy network (n=1099) reported (Luca G, Haba-Rubio J, Dauvilliers Y, Lammers GJ, Overeem S, Donjacour CE, Mayer G, Javidi S, Iranzo A, Santamaria J, Peraita-Adrados R, Hor H, Kutalik Z, Plazzi G, Poli F, Pizza F, Arnulf I, Lecendreux M, Bassetti C, Mathis J, Heinzer R, Jennum P, Knudsen S, Geisler P, Wierzbicka A, Feketeova E, Pfister C, Khatami R, Baumann C, Tafti M; European Narcolepsy Network. Clinical, polysomnographic and genome-wide association analyses of narcolepsy with cataplexy: a European Narcolepsy Network study. J Sleep Res. 2013 Oct;22(5):482-95. doi: 10.1111/jsr.12044. Epub 2013 Mar 18. PMID: 23496005., 2013).

For the purpose of this study only patients with narcolepsy with cataplexy were considered because of the uncertainty about the diagnosis of narcolepsy without cataplexy.

In order to create a network of sleep centers with expertise/interest in narcolepsy 79 centers from 27 Russian cities were connected in 2019. A total of 11 centers officially joined the Russian Narcolepsy Network (rnane.ru) and agreed to participate in the current study. A standardized questionnaire, similar to the one reported by the EU-NN in a series of 1099 patients (Luca G, Haba-Rubio J, Dauvilliers Y, Lammers GJ, Overeem S, Donjacour CE, Mayer G, Javidi S, Iranzo A, Santamaria J, Peraita-Adrados R, Hor H, Kutalik Z, Plazzi G, Poli F, Pizza F, Arnulf I, Lecendreux M, Bassetti C, Mathis J, Heinzer R, Jennum P, Knudsen S, Geisler P, Wierzbicka A, Feketeova E, Pfister C, Khatami R, Baumann C, Tafti M; European Narcolepsy Network. Clinical, polysomnographic and genome-wide association analyses of narcolepsy with cataplexy: a European Narcolepsy Network study. J Sleep Res. 2013 Oct;22(5):482-95. doi: 10.1111/jsr.12044. Epub 2013 Mar 18. PMID: 23496005., 2013) was sent by mail to the 11 centers. The questionnaire included the following parameters:

• Demographic characteristics: date of birth, gender, height, weight, BMI(body mass index) at diagnosis.
• Age at EDS (excessive daytime sleepines) onset and age at cataplexy onset. Investigators defined the age at onset of NC(narcolepsy with cataplexy) as the age at occurrence of EDS and/or cataplexy, determined during the clinical interview.
• Frequency of cataplexy attacks at diagnosis. The frequency of cataplexy was assessed by a scale from 1 to 5, reporting rare to very frequent cataplexy attacks: 1 = one or less cataplexy attacks per year; 2 = more than one cataplexy attack per year but less than one per month; 3 = more than one attack per month but less than one per week; 4 = more than one per week but less than one per day; 5 = at least one cataplexy attack per day.
• ESS (Epworth Sleepiness Scale) score at diagnosis.
• Polysomnographic variables [sleep onset latency at diagnosis, apnea-hypopnea index (AHI) and periodic leg movements during sleep index (PLMSI) when available] and MSLT results (mean sleep latency, number of SOREMPs) at diagnosis. Even if the recording procedures were different among centers, most of the patients underwent nocturnal in-lab PSG followed by an MSLT as part of the diagnostic evaluation. For PSG and MSLT, sleep latency was defined as the time from lights off to the first epoch scored as sleep. A SOREMP was defined as the occurrence of an epoch of REM(rapid eye movement) sleep within 15 min after the first epoch scored as sleep. Although MSLT was performed according to standard methods (Carskadon MA, Dement WC, Mitler MM, Roth T, Westbrook PR, Keenan S. Guidelines for the multiple sleep latency test (MSLT): a standard measure of sleepiness. Sleep. 1986 Dec;9(4):519-24. doi: 10.1093/sleep/9.4.519. PMID: 3809866.), the number of scheduled naps could be variable. To standardize the results, investigators calculated the percentage of SOREMPs of the total number of naps: percentage of naps with SOREMPs.

• Associated features, with particular attention to symptoms frequently reported with narcolepsy: sleep paralysis (SP); hypnagogic/hypnopompic hallucinations (HH); and poor nocturnal sleep.

• Co-morbidities (sleep-related, somatic or psychiatric) and treatment when available.

Inclusion criteria

• Signed written informed consent of the patient and/or parent/adoptive parent (in the case of a minor) to participate in the study;
• Age: 6-80 years;
• Gender: Men and women;
• Established diagnosis: Narcolepsy of type I and II (according to the criteria of the International classification of sleep disorders of 2014).

Exclusion criteria

• Refusal of the patient or his parent / adoptive parent (in the case of a minor) from further participation in the study;
• The occurrence of a serious illness or a significant deterioration of a disease unrelated to narcolepsy;
• Pregnancy started after inclusion.