Cataplexy is hypothesized to result from intrusion of REM sleep paralysis into wakefulness ( 4). Narcoleptics not only experience pronounced sleep disturbances, but they also experience cataplexy – the sudden unwanted loss of muscle tone during otherwise normal wakefulness. This review will describe our current understanding of the cells and circuits that mediate REM sleep in both health and disease.ĭisturbances in the normal control of REM sleep underlie cataplexy/narcolepsy and RBD, which are two common and serious sleep disorders. A distributed network of micro-circuits within the brainstem, forebrain, and hypothalamus is required for generating and sculpting REM sleep. Rapid eye movement (REM) sleep is characterized by rapid eye movements, cortical activation, vivid dreaming, skeletal muscle paralysis (atonia), and muscle twitches ( 1– 3). This review synthesizes our current understanding of mechanisms generating healthy REM sleep and how dysfunction of these circuits contributes to common REM sleep disorders such as cataplexy/narcolepsy and RBD. Determining how these circuits interact with the SubC is important because breakdown in their communication is hypothesized to underlie narcolepsy/cataplexy and REM sleep behavior disorder (RBD). REM sleep timing is controlled by activity of GABAergic neurons in the ventrolateral periaqueductal gray and dorsal paragigantocellular reticular nucleus as well as melanin-concentrating hormone neurons in the hypothalamus and cholinergic cells in the laterodorsal and pedunculo-pontine tegmentum in the brainstem. REM sleep paralysis is initiated when glutamatergic SubC cells activate neurons in the ventral medial medulla, which causes release of GABA and glycine onto skeletal motoneurons. It is hypothesized that glutamatergic SubC neurons regulate REM sleep and its defining features such as muscle paralysis and cortical activation. Within these circuits lies a core region that is active during REM sleep, known as the subcoeruleus nucleus (SubC) or sublaterodorsal nucleus. In the second part of the video, he starts falling down subsequently but is stabilised by a physical therapist.Rapid eye movement (REM) sleep is generated and maintained by the interaction of a variety of neurotransmitter systems in the brainstem, forebrain, and hypothalamus. Video 1 Eight-year-old boy with Niemann-Pick Type C showing bilateral loss of muscle tone being provoked by laughter. In our patient, however, it could not prevent the severe course.
This is relevant, as there is a treatment option which can have a favorable impact on the course of NPC. We think that cataplectic episodes can be a hint for early diagnosis of the disease. They occurred before the typical vertical gaze palsy started. These attacks are provoked by laughter and can sometimes be anticipated ( available in the online version). Then he had attacks of bilateral loss of muscle tone starting in head and neck region often spreading distally with subsequent falling. At 3 years, he started showing developmental regression, especially of speech. Our patient is an 8-year-old boy who was diagnosed with a mutation of NPC1 at age 6. Usually cataplexy occurs in narcoleptic patients and is also reported in Angelman's syndrome and animals, for example, in dogs.
However the association of lower orexin levels in cerebrospinal fluid (CSF) in patients with cataplexy suggests that these episodes can be a result of loss of orexin neurons. The pathophysiology of cataplexy, especially in the context of Niemann–Pick type C (NPC), is not fully understood. Cataplexy is described as a paroxysmal transient loss of muscle tone with retained consciousness provoked by strong emotions like laughter and fear.
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