Brain still injured after symptoms fade in mild TBIs

Brain abnormalities may still be present four months after a mild traumatic brain injury (mTBI), even after symptoms have subsided, according to a study published online Nov. 20 in Neurology.

“Studies of patients with complicated and symptomatic mild to moderate TBI indicate atrophy as a function of disease progression approximately 6 to 12 months postinjury. To our knowledge, no studies have directly assessed cortical thickness changes prospectively after mTBI,” wrote Josef M. Ling, of the University of New Mexico in Albuquerque, and colleagues.

Thus, the authors designed a study that investigated potentially time-dependent biomarkers of gray matter injury in 50 patients with mTBI. The researchers compared participants to 50 healthy people of similar age and education.

The study’s subjects were imaged within 21 days of injury and and then again within four months post-injury. All participants underwent brain scans and were tested for their memory, thinking skills, and other symptoms such as anxiety and depression. Measures of diffusion and atrophy were obtained for cortical and subcortical structures to characterize effects of injury as a function of time.

People who had concussions had more self-reported problems with memory and thinking skills, physical problems like headaches and dizziness, and emotional problems such as depression and anxiety than people who had not had concussions after two weeks. By four months after the injury, the symptoms were significantly reduced by up to 27 percent.

Interestingly, people who had concussions also had evidence of irregularities in the gray matter in the frontal cortex area of both sides of the brain, based on diffusion tensor imaging scans. The increase equated to about 10 percent compared to the healthy controls. These abnormalities were still seen four months after the concussion. In contrast, there was no evidence of cellular loss on scans.

A potential explanation for the brain abnormalities could be cytotoxic edema, which results from changes in which fluids are located in and around brain cells, or reactive gliosis, which is the change in glial cells’ shape in response to damage to the central nervous system.

“Collectively, these findings suggest potentially different recovery courses for neurobehavioral (more rapidly resolving) and physiologic (more slowly resolving) signs of mTBI,” the study’s authors wrote.