Surprising Result
The investigators also found a link between time since the most recent mTBI and iron accumulation in the bilateral temporal, right hippocampus, posterior and superior corona radiata, bilateral thalamus, right precuneus and cuneus, right lingual, and right cerebellum.
“The more time that passed since the concussion occurred, the more likely that people had higher iron levels,” said Dr. Nikolova.
It’s perhaps to be expected that the length of time since injury is linked to iron accumulation in the brain as iron accumulates over time. But even those whose injury was relatively recent had higher amounts of iron, which Dr. Nikolova said was “surprising.”
“We thought iron accumulates over time so we were thinking maybe we should be doing a longitudinal study to see what happens, but we see definite iron accumulation due to injury shortly after the injury,” she said.
There was no association between iron accumulation and symptom severity as measured by SCAT scores.
Questions Remain
It’s unclear why iron accumulates after an injury or what the ramifications are of this accumulation, Dr. Nikolova noted.
The imaging used in the study doesn’t distinguish between “bound” iron found after a hemorrhage and “free” iron in the brain. The free iron type has been shown to be increased after TBI and is “the stuff you should be afraid of,” Dr. Nikolova said.
Iron’s role in the metabolic process is important, but must be closely regulated, she said. Even a small accumulation can lead to oxidative stress.
Researchers are investigating whether the findings would be similar in mTBI but no headache and want to increase the number of study participants. A larger, more diverse sample would allow them to probe other questions, including whether iron accumulation is different in men and women. More data could also eventually lead to iron accumulation becoming a biomarker for concussion and PTH, Dr. Nikolova said.
“If you know a certain person has that biomarker, you might be able to administer a drug or some therapeutic procedure to prevent that iron from continuing to accumulate in the brain.”
Chelation drugs and other therapies may clear iron from the body but not necessarily from the brain.
Commenting on the study for this news organization, Frank Conidi, MD, director, Florida Center for Headache and Sports Neurology, Port St. Lucie , said that the study supports the hypothesis that concussion “is not a benign process for the brain, and the cumulative effect of repetitive head injury can result in permanent brain injury.”
He said that he found the accumulation of iron in cortical structures particularly interesting. This, he said, differs from most current research that suggests head trauma mainly results in damage to white matter tracts.
He prefers the term “concussion” over “mild traumatic brain injury” which was used in the study. “Recent guidelines, including some that I’ve been involved with, have defined mild traumatic brain injury as a more permanent process,” he said.
The study was supported by the US Department of Defense and National Institutes of Health. No relevant conflicts of interest were disclosed.
A version of this article appeared on Medscape.com.