Children who undergo radiation therapy as part of their treatment for medulloblastoma—the most common malignant brain tumor in kids—are less likely to recall the specifics of recent personal events, according to a study published this week in the Journal of Neuroscience. The patients’ pre-radiation memories remained intact.
Melanie Sekeres, PhD, first author of the paper and director of Sekeres Memory Laboratory at Baylor University, said her team’s study found medulloblastoma survivors had reduced volume in their hippocampuses post-RT treatment compared to healthy controls—something normally seen in Alzheimer’s or dementia patients.
“The surprise, and the upside, is that episodic memories from before the children’s treatment were spared,” Sekeres said in a Baylor release. That’s a rarity in older patients.
For their trial, Sekeres and her colleagues recruited 13 child survivors of brain cancer who’d received radiotherapy and chemo at least a year before the study’s baseline, and matched those patients with 28 healthy controls. All kids completed the Children’s Autobiographical Interview, a standardized memory test during which children were asked to recall a very old memory from before RT and a more recent one from within the past month, and underwent MRI. All testing was completed at the Hospital for Sick Children in Toronto.
Sekeres said the structure of the interview was critical, because it allowed kids to freely recall memories without too much prompting or guidance. But, she said, the group who’d undergone radiation therapy had considerable trouble citing specifics about recent life events.
“They have a hard time forming new, detailed memories,” she said. “Such specific details might seem trivial, but these are precisely the kinds of details that allow us to vividly replay important events in our lives. For most events, though, even healthy people forget a lot of specific details over time because we typically don’t need to retain all that incidental information.”
Some forgetting is “normal and adaptive,” Sekeres said, and it’s not uncommon for us to remember just the “gist” of an event. The kids with medulloblastoma were still able to recall older events from before their treatment with as much clarity as the healthy children.
The authors said the cancer patients likely showed reduced volume in their hippocampuses as a result of the RT, because radiation can directly impact the development of new cells in the nervous system, including in the hippocampus.
“The study identifies an area of cognition that is inadvertently impacted by standard treatment methods, which has real consequences for the quality of life of the survivors,” Sekeres said. “The physicians’ ultimate goal is to allow their patients to survive and to live as well as possible. Although these treatments are often crucial in the effective management of the cancer, if the physicians and the family know there are these unintended side effects, that may be an additional factor to consider when exploring the treatment options.”