The mystery of 'chemobrain' and why imaging isn't revealing all the clues

Three biobehavioral and psychological specialists from the National Cancer Institute (NCI) published an appeal to neuroscientists on June 12 in Trends in Neuroscience, asking for further assistance in researching the cognitive effects of mental fog—known officially as cancer-related cognitive impairment or "chemobrain."

Why chemobrain occurs, how long it lasts and what health problems it causes are currently unknown. The real mystery, however, lies in the wide-ranging estimates of how many cancer patients are actually affected by chemobrain, as reported on June 13 by the Los Angeles Times. 

"Somewhere between 17 percent and 75 percent of patients with malignancies that don’t affect the central nervous system report the sensation that a mental fog has set in," according to the article. "That the latest prevalence figures stretch from 17 percent to 75 percent of cancer patients suggests that existing tests are missing their mark." 

MRI and functional MRI scans have shown reduced volumes of white matter, long-term loss in cortical structure volume and reduced connectivity in the default mode network of cancer patients' brains even before they have undergone treatment, according to the article.  

However, imaging may not be enough to find answers, according to Todd Horowitz, PhD, a cognitive psychologist and program director in the NCI's Division of Cancer Control and Population Sciences who co-authored the paper in Trends in Neuroscience.

"We need an infusion of new ideas—cognitive neuroscience would help us characterize the deficits people have and allow us to connect them to particular brain systems. Patients and their families want to know what to expect during and after treatment," Horowitz told The LA Times. 

"A better understanding of all aspects of chemobrain will help cancer patients and their families make better decisions and may help identify treatments or strategies to reduce or prevent it."