Children who have undergone radiotherapy for medulloblastoma or ependymoma might easily remember things that happened to them before their treatment, but struggle to remember what happens to them afterward.
While lifesaving, radiotherapy is known to be linked with reduced hippocampal volume and neurogenesis, and it can disrupt brain development, Dr. Melanie J. Sekeres of the Hospital for Sick Children and the University of Toronto and colleagues note in The Journal of Neuroscience, online August 20.
"These findings have significant implications for these patients' quality of life," Dr. Sekeres told Reuters Health by email. "The ability to form and retain detailed personal memories of important events in one's life is a big part of what gives our lives rich meaning."
Dr. Sekeres and her colleagues investigated thirteen 7- to 18-year-old survivors of posterior fossa tumors (PFTs) through the brain tumor program at one pediatric hospital, as part of a larger clinical research study; 12 were treated for medulloblastoma and one for ependymoma.
Complete Children's Autobiographical Interview (CAI), standardized memory testing, and neuroimaging data were available for all participants.
Radiotherapy and chemotherapy
The children had undergone surgical resection of the tumor followed by radiotherapy and chemotherapy at least one year before taking part in the study, and they were age-matched with nine healthy controls. An additional 19 age-matched healthy controls were recruited for the CAI section of the study through ads in the hospital and community.
The researchers asked the participants to recall two separate memories: an event from the previous month and one from as far back in time as they could remember. They then used the CAI to retrospectively evaluate the patients' memories for events that either preceded or followed their treatment.
Compared to the healthy controls, the patients treated for brain tumor recalled fewer details, such as time and place, from their recent memory; but the patients and controls recalled a similar amount of detail from their pre-treatment memory.
The authors acknowledge that the results may be affected by treatment effects linked with anesthesia and chemotherapy and by mechanisms including effects on white matter, glia, vasculature, synaptogenesis, and neuroinflammation.
"The clinician's primary concern is choosing a course of treatment that will increase the likelihood of patient survival, and consideration of potential side effects on cognition are secondary concerns," Dr. Sekeres said.
"When deciding on treatment options, clinicians need to consider that standard treatment methods may impair their patient's ability to form new autobiographical memories," Dr. Sekeres said.
"These findings would not affect patient care, but they may lead to better understanding of the deficits and mechanism of those deficits in pediatric patients who have had cranial radiation," he added. "This information gives us more reason to work towards reduction or avoidance of cranial radiation in patients."