Patients who recover well from serious head injuries complain of "mental fatigue"

Brain imaging experts have found a distinct "brain signature" in patients who have recovered from head injuries that shows their brains may have to work harder than the brains of healthy people to perform at the same level.

The patients in the study had diffuse axonal injury (DAI), the most common consequence of head injuries resulting from motor vehicle accidents, falls, combat-related blast injuries, and other situations where the brain is rattled violently inside the skull causing widespread disconnection of brain cells.

"Our imaging data revealed that the DAI patient brains showed a greater recruitment of regions of the prefrontal cortex and posterior cortices compared to healthy controls," said Dr. Gary Turner, who led the study at Baycrest's Rotman Research Institute and the University of Toronto with senior Rotman scientist Dr. Brian Levine. The study is published in the Sept.9 issue of Neurology, the medical journal of the American Academy of Neurology.

Even though the head injury patients performed as well as the healthy controls on a series of working memory tests that measured their ability to organize, plan and problem solve, the fact their brains had to work harder is an indication of "reduced cognitive efficiency", explained Dr. Turner, who is now with the Helen Wills Neuroscience Institute at the University of California, Berkeley.

The eight patients in the Baycrest study had been in motor vehicle accidents several years prior, sustaining significant brain injuries that left them comatose for various lengths of time; yet all patients made good recoveries as evidenced by a return to pre-injury employment or school. Their fMRI scans were compared to 12 healthy adults, matched to the patients for age and education.

The Baycrest study is the first to recruit head injury patients and healthy controls that were evenly matched in cognitive performance from the outset - thus yielding the strongest evidence to date of this "working harder" effect in recovered head injury patients.