Caroline Edmonds - Research Fellow

The use of Magnetic Resonance Imagery (MRI) in examining the effects of dehydration on brain structure and function in healthy humans

Marcus S Smith and Matthew J Kempton

Objectives: The ability to determine the effects of dehydration on brain structure and function has improved recently following advancements in magnetic resonance imaging (MRI) technology. Previous research reported reductions in total brain volume following 16-h fluid restriction and increases in ventricular volume.  Study 1 considered which image analysis was more sensitive to dehydration in adults. Study 2 considered whether dehydration effects on the brain were also observed in adolescents.

Design: The adult brain appears susceptible to dehydration; we examined whether similar changes occur in the developing adolescent brain.  A manual point counting technique (MEASURE) was compared to an automated voxelwise analysis (SIENA) of brain volume.

Methods:  In Study 1 seven adults (aged 23.8+4.1yr) and in Study 2 ten adolescents (aged 16.8+0.4yr) were scanned whilst hydrated and dehydrated. Dehydration was induced by cycling intermittently for 90-min whilst wearing impermeable plastic clothing. In Study 1, total brain volume was determined using MEASURE and SIENA. In Study 2, SIENA was accompanied by BOLD analysis of executive function.

Results: In Study 1, a 2.2+0.5% body mass decrease following dehydration showed ventricular expansion. SIENA was more sensitive than MEASURE.  In Study 2, a 1.6+0.3% body mass decrease showed lateral ventricular enlargement correlated with body mass reduction and inefficient use of brain metabolic activity following dehydration.

Conclusions: Brain structure changes were observed in adolescent and adult brains following acute dehydration. In adolescents, executive functions including planning and visuo-spatial processing were adversely affected.  Given these findings the effect of dehydration on school academic performance warrants future investigation.

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