Substantial and reversible brain gray matter reduction but no acute brain lesions in ultramarathon runners: experience from the TransEurope-FootRace Project

Abstract

BackgroundDuring the extremely challenging 4,487 km ultramarathon TransEurope-FootRace 2009, runners showed considerable reduction of body weight. The effects of this endurance run on brain volume changes but also possible formation of brain edema or new lesions were explored by repeated magnetic resonance imaging (MRI) studies.MethodsA total of 15 runners signed an informed consent to participate in this study of planned brain scans before, twice during, and about 8 months after the race. Because of dropouts, global gray matter volume analysis could only be performed in ten runners covering three timepoints, and in seven runners who also had a follow-up scan. Scanning was performed on three identical 1.5 T Siemens MAGNETOM Avanto scanners, two of them located at our university. The third MRI scanner with identical sequence parameters was a mobile MRI unit escorting the runners. Volumetric 3D datasets were acquired using a magnetization prepared rapid acquisition gradient echo (MPRAGE) sequence. Additionally, diffusion-weighted (DWI) and fluid attenuated inversion recovery (FLAIR) imaging was performed.ResultsAverage global gray matter volume as well as body weight significantly decreased by 6% during the race. After 8 months, gray matter volume returned to baseline as well as body weight. No new brain lesions were detected by DWI or FLAIR imaging.ConclusionsPhysiological brain volume reduction during aging is less than 0.2% per year. Therefore a volume reduction of about 6% during the 2 months of extreme running appears to be substantial. The reconstitution in global volume measures after 8 months shows the process to be reversible. As possible mechanisms we discuss loss of protein, hypercortisolism and hyponatremia to account for both substantiality and reversibility of gray matter volume reductions. Reversible brain volume reduction during an ultramarathon suggests that extreme running might serve as a model to investigate possible mechanisms of transient brain volume changes. However, despite massive metabolic load, we found no new lesions in trained athletes participating in a multistage ultramarathon.See related commentary http://www.biomedcentral.com/1741-7015/10/171

Responses of the Human Brain to Mild Dehydration and Rehydration Explored In Vivo by1H-MR Imaging and Spectroscopy

“…Freund et al 15 demonstrated a reversible volume reduction of cerebral gray matter (6%) after 2 months of daily running during an ultramarathon, which is in line with the reversible cortical thinning (0.19%) on dehydration reported in our study. On the other hand, a recent study with low sample size 14 failed to reveal thinning of the cerebral cortex and shrinking of the hypothalamus/ thalamus, which are reversed on rehydration.…”

“…Similarly, Streitbürger et al 14 demonstrated an increase in brain volume on ingestion of 3–4 L of water; however, they failed to show an effect of dehydration on brain volume by 2 days of restricted water intake. In a study on ultramarathon runners, Freund et al 15 described a reversible 6% cortical volume reduction with 2 months of daily running. Currently, there are no in vivo data on tissue water changes and associated morphometric changes involved in the osmoadaptation of normal brains.…”

Recent Advances in Neuroimaging to Model Eating Disorder Neurobiology

“…Only some studies corrected for age or overall brain volumes, some studies distinguished restricting from binge eating/purging anorexia nervosa while others did not, and the effects of comorbid diagnoses or medication were often not taken into account [12••]. Furthermore, the effects of acute dehydration and starvation [20] as well as excessive exercise [21] most likely have significant confounding effects that may not be directly related to the underlying ED-specific pathophysiology. Importantly, the global effects of malnutrition may obscure particularly in studies that showed widespread alterations across large cortical regions brain pathology that drives ED behavior.…”

Evidence from neuroimaging to explore brain plasticity in humans during an ultra-endurance burden

“…Repeated and strenuous running exercises constitute a remarkable physical stressor requiring important mental effort. An example of this is the 64 day ultramarathon covering about 4,500 km from Bari, Italy to the North Cape, Norway used in the study of Freund et al [3], published in BMC Medicine . We expect the ultramarathon model to involve concurrent physical and mental demands.…”

“…Thus, it can probably be considered as one of the main challenges that would allow us to explore the finite resources of the human brain under natural field settings. Freund et al [3] have successfully explored some biometrical data and the cerebral structural changes occurring in 10 runners in response to chronic endurance running exposure, with the help of three identical magnetic resonance (MR) scanners (one was a mobile MR unit mounted on a truck trailer across Europe). The results of this unique study, which revealed no brain lesions, suggest that ultra-endurance runners likely have important mental effort prerequisites and an adapted training workload to cope with demands of ultramarathon running.…”