Rapid eye movement sleep periodic leg movements in patients with spinal cord injury

We describe three spinal cord injury cases exhibiting periodic leg movements (PLMs) in both rapid eye movement (REM) and nonrapid eye movement (NREM) sleep. The difference in the average periodicity in REM and NREM sleep was modest, but was generally shorter in REM than in NREM sleep. However, the variability associated with the PLMs was nearly three to six times smaller in REM than in NREM sleep, suggesting that the periodicity of the PLMs in REM sleep was more precise than in NREM sleep. The finding of PLMs in these patients suggests that a spinal cord injury may permit the expression of a spinal PLM generator, which may be an unusual presentation of a spinal locomotor generator. The PLM generator would be displayed when the descending inhibitory spinal pathways are interrupted by a spinal injury. The rapid periodicity of the PLM generator in REM sleep, compared with NREM sleep, may result from an increase in sympathetic activity normally accompanying this sleep state. Alternative explanations for the occurrence of PLMs in spinal injury are the influence of adverse sleeping position, age, an increase in circulating catecholamines and peripheral perfusion. We conclude that the presence of PLMs may be an important, but neglected, sleep disorder in spinal cord patients. Therefore, health care professionals should be aware of the possibility of sleep-related PLMs when these patients have sleep and/or waking complaints.