After the completion of a voluntary movement, a synchronization of cortical beta rhythms is recorded over the contralateral central region, which is assumed to reflect the termination of the motor command. In order to test this hypothesis, we compared in eight healthy subjects the synchronization of EEG beta rhythms following active and passive index extension. The passive movement was also performed after deafferentation by ischaemic nerve block in three subjects. Beta synchronization was present in all subjects after both active and passive movements, and disappeared under ischaemia in all three subjects. Post-movement beta synchronization can not solely be explained by an idling motor cortex. It may also, at least in part, reflect a movement-related somatosensory processing.
This paper reviews the characteristics of sleep disorders found in people at a greater risk of dementia: the elderly adult, patients with mild cognitive impairment (MCI) and those with neurodegenerative diseases. The frequency of sleep architecture modifications and circadian rhythm sleep disturbances increases with age. Although around 40% of older adults complain of poor sleep, true sleep disorders are far less prevalent in healthy older adults and are frequently associated with comorbidities. The sleep disorders observed in Alzheimer's disease (AD) patients are often similar to (but more intense than) those found in non-demented elderly people. Poor sleep results in an increased risk of significant morbidities and even mortality in demented patients and constitutes a major source of stress for caregivers. The prevalence of primary sleep disorders such as rapid eye movement (REM) sleep behavior disorders (RBDs), restless legs syndrome (RLS), periodic limb movements (PLMs) and sleep-disordered breathing increases with age. There are no published data on RLS and PLMs in demented persons but RBDs and sleep apnea syndrome have been studied more extensively. In fact, RBDs are suggestive of Lewy body dementia (LBD) and are predictive for neurodegeneration in Parkinson's disease. Obstructive sleep apnea (OSA) shares common risk factors with AD and may even be an integral part of the pathological process in AD. In MCI patients, the hypotheses in which (i) sleep disorders may represent early predictive factors for progression to dementia and (ii) MCI is symptomatic of a non-diagnosed sleep disorder remain to be elucidated. Guidelines for drug and non-drug treatments of sleep disorders in the elderly and in demented patients are also considered in this review. In healthy but frail elderly people and in early-stage AD patients, sleep should be more thoroughly characterized (notably by using standardized interviews and polysomnographic recording).
The frequency of cefepime-induced neurotoxicity is probably underestimated. Monitoring of renal function and close neurological survey in treated patients should allow an early diagnosis of this complication. Urgent hemodialysis seems the best therapeutic method to obtain a rapid neurological improvement.
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