Familial dystonic choreoathetosis with myokymia; a sleep responsive disorder. Byrne E,White O,Cook M Journal of neurology, neurosurgery, and psychiatry A family is presented with paroxysmal dystonic choreoathetosis transmitted as a dominant trait over five generations. The family is unusual in the marked responsiveness of the episodes to short periods of sleep in several members, in the very variable age of onset, and in the association with prominent myokymia in some cases. These overlap features suggest a link between paroxysmal dystonic choreoathetosis and familial paroxysmal ataxia with myokymia. 10.1136/jnnp.54.12.1090

REM Sleep Behavior Disorder. Bassetti Claudio L,Bargiotas Panagiotis Frontiers of neurology and neuroscience Rapid eye movement sleep behavior disorder (RBD) is a brain disorder, characterized by the dream enactment during rapid eye movement (REM) sleep due to a lack of physiologic muscle atonia and increased muscle twitching. Schenk was the first to describe this disorder in 1986; however, few authors reported in the 1970-1980s loss of physiological muscle atonia combined with dream enactment in the course of brainstem disorders and as a consequence of alcoholism and antidepressant treatment. RBD affects less than 1% of the adult population, but can be found in up to 25-50% of neurodegenerative disorders including Parkinson's disease, multisystem atrophy, and dementia with Lewy body. In the last decade, many studies provided evidence that RBD precedes parkinsonian motor signs by several years, suggesting that RBD should no longer be considered a complication but a part of the prodromal phase of these diseases. Etiologically, primary (idiopathic RBD) and several secondary forms in addition to neurodegeneration (related to focal brainstem damage, narcolepsy, autoimmune disorders, and drugs) are known. Pathophysiologically, brainstem and supratentorial mechanisms involving glutamatergic, glycinergic, and GABA-ergic neurotransmission have been implicated. Recently, an animal model of RBD has been described. Clinical features consist of characteristic nocturnal behaviors, but also daytime symptoms including excessive sleepiness and cognitive alterations. The diagnosis of RBD is made according to international diagnostic criteria, based on medical history, and video-polysomnographic features. Current treatment strategies include actions which ensure a safe sleep environment, the avoidance of triggering/exacerbating factors and if necessary pharmacological (mainly clonazepam and melatonin) and non-pharmacological (e.g., behavioral measures) interventions. Future research should clarify the exact sleep-wake characteristics of RBD (also beyond REM sleep) and their evolution over time, the contribution of brainstem but also supratentorial mechanisms to its pathophysiology, and the (early?) diagnostic and (causative?) treatment consequences of RBD in the context of neurodegeneration. 10.1159/000478914

Control of motoneuron function and muscle tone during REM sleep, REM sleep behavior disorder and cataplexy/narcolepsy. Peever J Archives italiennes de biologie REM sleep triggers a potent suppression of postural muscle tone - i.e., REM atonia. However, motor control during REM sleep is paradoxical because overall brain activity is maximal, but motor output is minimal. The skeletal motor system remains quiescent during REM sleep because somatic motoneurons are powerfully inactivated. Determining the mechanisms triggering loss of motoneuron function during REM sleep is important because breakdown in REM sleep motor control underlies sleep disorders such as REM sleep behavior disorder (RBD) and cataplexy/narcolepsy. For example, RBD is characterized by dramatic REM motor activation resulting in dream enactment and subsequent patient injury. In contrast, cataplexy a pathognomonic symptom of narcolepsy - is caused by the involuntary onset of REM-like atonia during wakefulness. This review highlights recent work from my laboratory that examines how motoneuron function is lost during normal REM sleep and it also identifies potential biochemical mechanisms underlying abnormal motor control in both RBD and cataplexy. First, I show that both GABAB and GABAA/glycine mediated inhibition of motoneurons is required for generating REM atonia. Next, I show that impaired GABA and glycine neurotransmission triggers the cardinal features of RBD in a transgenic mouse model. Last, I show that loss of an excitatory noradrenergic drive onto motoneurons is, at least in part, responsible for the loss of postural muscle tone during cataplexy in narcoleptic mice. Together, this research indicates that multiple transmitters systems are responsible for regulating postural muscle tone during REM sleep, RBD and cataplexy. 10.4449/aib.v149i4.1257