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Noninvasive Imaging of Brain Oxygen Metabolism in Children with Primary Nocturnal Enuresis During Natural Sleep

Bing Yu, Mingzhu Huang, Xu Zhang, Hongwei Ma, Miao Peng, and Qiyong Guo. China

Human Brain Mapping 2017 Feb 14. doi: 10.1002/hbm.23538. [Epub ahead of print]

Commentary by Konstantinos Kamperis

A new imaging approach reveals differences in brain oxygen metabolism in children with enuresis

There is accumulating evidence that nocturnal enuresis may in some cases be the result of sleep disordered breathing and obstructive sleep apnea. In such children treating the cause of abnormal respiration during sleep may lead to improvement or resolution of bedwetting. The authors use a novel approach utilizing a standard 3 T MR scanner that enables noninvasive and reproducible measurement of global cerebral rate of oxygen metabolism. Forty-nine children with enuresis and 53 controls were recruited and subjected to MR scans during their natural sleep without prior sleep deprivation or use of sedatives. Oxygenation was measured by pulse oximetry. Although a significant number of children failed to fall asleep in the MR scanner the authors were able to demonstrate significant differences between children with bedwetting and controls, based on the remaining children in terms of brain oxygen metabolism. Children with enuresis seem to share higher oxygen metabolism values as well as higher oxygen extraction fraction to maintain adequate supply.

The interpretation of these findings is challenging. The authors speculate that this need for higher oxygen consumption may reflect compensation mechanism for lower brain network efficiency, which in turn may be the result of maturation delay. If neural network in these children is less efficient more processing load may be needed necessitating more oxygen. The authors further speculate that oxygen extraction fraction may indicate that these children may be more prone to hypoxia, which can lead to sleep fragmentation and high arousal thresholds.

The question remains. Are the differences in brain oxygen metabolism directly related to enuresis pathophysiology? Studies on brain function and metabolism are difficult and even more demanding if these parameters need be evaluated during sleep in children. Although these results seem interesting they are still very preliminary and their significance in the pathophysiology of nocturnal enuresis needs further investigation.