The spectrum of REM sleep-related episodes in children with type 1 narcolepsy

Abstract

Type 1 narcolepsy is a central hypersomnia due to the loss of hypocretin-producing neurons and characterized by cataplexy, excessive daytime sleepiness, sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep. In children, close to the disease onset, type 1 narcolepsy has peculiar clinical features with severe cataplexy and a complex admixture of movement disorders occurring while awake. Motor dyscontrol during sleep has never been systematically investigated. Suspecting that abnormal motor control might affect also sleep, we systematically analysed motor events recorded by means of video polysomnography in 40 children with type 1 narcolepsy (20 females; mean age 11.8 ± 2.6 years) and compared these data with those recorded in 22 age- and sex-matched healthy controls. Motor events were classified as elementary movements, if brief and non-purposeful and complex behaviours, if simulating purposeful behaviours. Complex behaviours occurring during REM sleep were further classified as 'classically-defined' and 'pantomime-like' REM sleep behaviour disorder episodes, based on their duration and on their pattern (i.e. brief and vivid-energetic in the first case, longer and with subcontinuous gesturing mimicking daily life activity in the second case). Elementary movements emerging either from non-REM or REM sleep were present in both groups, even if those emerging from REM sleep were more numerous in the group of patients. Conversely, complex behaviours could be detected only in children with type 1 narcolepsy and were observed in 13 patients, with six having 'classically-defined' REM sleep behaviour disorder episodes and seven having 'pantomime-like' REM sleep behaviour disorder episodes. Complex behaviours during REM sleep tended to recur in a stereotyped fashion for several times during the night, up to be almost continuous. Patients displaying a more severe motor dyscontrol during REM sleep had also more severe motor disorder during daytime (i.e. status cataplecticus) and more complaints of disrupted nocturnal sleep and of excessive daytime sleepiness. The neurophysiological hallmark of this severe motor dyscontrol during REM sleep was a decreased atonia index. The present study reports for the first time the occurrence of a severe and peculiar motor disorder during REM sleep in paediatric type 1 narcolepsy and confirms the presence of a severe motor dyscontrol in these patients, emerging not only from wakefulness (i.e. status cataplecticus), but also from sleep (i.e. complex behaviours during REM sleep). This is probably related to the acute imbalance of the hypocretinergic system, which physiologically acts by promoting movements during wakefulness and suppressing them during sleep.

Objective rest–activity cycle analysis by actigraphy identifies isolated rapid eye movement sleep behavior disorder

“…Rapid eye movement sleep behaviour disorder has been categorized into isolated RBD (iRBD) and secondary RBD [3], when associated with other neurological/neurodegenerative disorders [4][5][6], autoimmune diseases [7], or brainstem lesions [8]. Results from long-term follow-up studies [9], investigations in patients with long-standing iRBD [10], and studies evaluating biomarkers of synuclein-related neurodegeneration (including a-synuclein accumulation outside the central nervous system) [11,12], provided consistent evidence that iRBD is an early-phase asynucleinopathy, eventually evolving into Parkinson's disease, dementia with Lewy bodies or multiple system atrophy [13].…”

Biomarkers for REM sleep behavior disorder in idiopathic and narcoleptic patients

“…All sleep stages were considered, except for wakefulness before and after sleep onset. Movements were scored in both NREM and REM sleep stages and classified as elementary (if brief and nonpurposeful, as, e.g., stereotypies, facial grimacing, pelvic movements) or complex (if longer and purposeful, hence mimicking a scenic behavior, likely linked to a dream mentation) . Motor events were judged as having a stereotyped pattern if they tended to occur with the same/similar pattern on different occasions.…”

Catatonia and the immune system: a review

“…Cataplexy usually lasts for up to 2 min, but occasionally status cataplecticus lasting for hours to days can occur. 71 This occurrence has been hypothesised to be due to either a prolonged emotional response to the original stimulus, or an emotional response to the cataplexy per se. Here, we show a comparison between cataplexy and catatonia (table 4).…”