Different Circadian Rest-Active Rhythms in Kleine-Levin Syndrome: A prospective and case-control study

STUDY OBJECTIVES

Kleine-Levin-syndrome (KLS) is a rare recurrent hypersomnia. Our study aimed at monitoring the movements of patients with KLS using actigraphy and evaluating their circadian rhythm.

METHODS

Twenty young patients with KLS and 14 age-matched controls were recruited. Each individual wore an actigraphy for more than 6 months to monitor at least two attacks. Controls kept wearing the device for at least 7 days.The activity counts were averaged in hourly basis and the day-to-night amplitude was quantified by the differences of the averaged activity counts during daytime and nighttime. The hourly activities of different days were aligned and averaged to construct the circadian profile. Parametric and nonparametric estimation of circadian rhythm was calculated. We applied detrended fluctuation analysis to evaluate the temporal correlations beneath the activity fluctuations at multiple time scales.

RESULTS

Circadian rhythm in asymptomatic period showed no significant difference compared to the controls. During hypersomnia attack, the amplitude of the circadian rest-active rhythms drastically decreased and decreased inter-daily stability (IS) was found, as well as significant decreased M10 and short-time fractal correlation (α1). Drastically decreased mean and standard deviation of activity were noted, compared to the pre-attack phase and recovery phase.α1 and M10 increased during the late attack phase, and overcompensated IS was noted in the recovery phase.

CONCLUSIONS

This study confirmed that circadian rest-active rhythms was affected when KLS hypersomnia attack. Several parameters including M10, IS and α1 may be physiological markers of KLS, which can help to predict the end of hypersomnia episodes.

Kleine-Levin syndrome is associated with LMOD3 variants

Kleine-Levin syndrome (KLS) is a rare periodic hypersomnia with associated behavioural abnormalities but with often favourable prognosis. There is excess risk of KLS in first-degree relatives, suggesting a strong genetic contribution. So far, no mutation is identified in KLS and comprehensive genetic analysis of affected individuals is lacking. Here we performed whole genome single-nucleotide polymorphism (SNP) genotyping and exome sequencing in a large family with seven affected members. The identified gene with a mutation was resequenced in 38 sporadic KLS patients and the expression of the gene product was mapped in the mouse brain. Linkage analysis mapped the disease locus to chromosome 3 and exome analysis identified a heterozygous missense variant in LMOD3 (p.E142D) in the linkage interval. The variant was found to segregate in all affected and one presumably unaffected member of the family. Resequencing LMOD3 in 38 other KLS patients and their families revealed three other low frequency or rare missense variants in seven cases that were inherited with incomplete penetrance. LMOD3 is expressed in the brain and colocalized with major structures involved in the regulation of vigilance states. LMOD proteins are structural proteins and seem to be developmentally regulated. Our findings suggest that KLS might be a structural/neurodevelopmental brain disease.