MONDAY, March 15 (HealthDay News) -- Brain stem cell loss is the reason why repeated anesthesia causes memory and learning problems in children, Swedish researchers suggest.

"Pediatric anesthetists have long suspected that children who are anesthetized repeatedly over the course of a few years may suffer from impaired learning and memory," study author Klas Blomgren said in a news release.

The University of Gothenburg team conducted experiments on rats and mice to find out what happens to brain stem cells when they're exposed to strong magnetic fields. The researchers discovered that the magnetic fields had no effect on the rodents, but repeatedly being anesthetized for the magnetic imaging resonance scans did have an impact on brain stem cells.

"We found that repeated anesthesia wiped out a large portion of the stem cells in the hippocampus, an area of the brain that is important for memory. The stem cells in the hippocampus can form nerve and glial cells, and the formation of nerve cells is considered important for our memory function," Blomgren said.

The anesthesia-associated memory problems in the young rodents persisted into adulthood, but weren't seen in adults animals who were anesthetized. This may be because stem cells are more sensitive in younger brains.

"Despite extensive attempts, we have not been able to understand exactly what happens when the stem cells are wiped out. We couldn't see any signs of increased cell death, but are speculating that the stem cells lose their ability to divide," Blomgren said.

Physical activity may help form new cells that improve memory, according to the researchers.

The study appears in the Journal of Cerebral Blood Flow & Metabolism.

More information

The Nemours Foundation has more about anesthesia and children.

-- Robert Preidt

SOURCE: University of Gothenburg, news release, March 8, 2010

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