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Sleep Disorder May Influence Memory Loss
The study focused on structures called mammillary bodies, so named because they resemble small breasts, on the underside of the brain. The University of California, Los Angeles (UCLA) team scanned the brains of 43 sleep apnea patients, using magnetic resonance imaging (MRI) to collect high-resolution images of the entire brain, including slices of the mammillary bodies.
The structures' small size and proximity to bone and fluid make them difficult to measure by conventional MRI. So the researchers manually traced the mammillary bodies from the high-resolution scans and calculated their volumes from the hand-drawn outlines. When they compared the results to images of 66 control subjects matched for age and gender, the scientists discovered that the sleep apnea patients' mammillary bodies were nearly 20 percent smaller, particularly on the left side.
"The findings are important because patients suffering memory loss from other syndromes, such as alcoholism or Alzheimer disease, also show shrunken mammillary bodies," said lead author Rajesh Kumar, a UCLA assistant researcher in neurobiology. Repeated drops in oxygen lead to the brain injury, hypothesizes principal investigator Ronald Harper, a distinguished professor of neurobiology at the David Geffen School of Medicine at UCLA.
During an apnea episode, the brain's blood vessels constrict, starving its tissue of oxygen and causing cellular death. The process also incites inflammation, which further damages the tissue. "The reduced size of the mammillary bodies suggests that they've suffered a harmful event resulting in sizable cell loss," Harper said. "The fact that patients' memory problems continue despite treatment for their sleep disorder implies a long-lasting brain injury."
In a future study, Harper and Kumar will explore whether taking supplemental vitamin B1 helps restore sleep apnea patients' memory. The vitamin helps move glucose into the cells, preventing their death from oxygen starvation.
MEDICA.de; Source: University of California, Los Angeles (UCLA), Health Sciences