Rat study shows concussions can cause robust thickening of the skull
Repeated knocks to the head are known to carry increased risks to our neurological health, but a new study has sought to fill in important details around what they might mean for the skull. Experiments carried out on rats showed that blows to the head at regular intervals led to a “robust” increase in skull thickness and volume, with scientists now looking to explore what this means for its ability to protect the brain from injury.
The study was led by researchers at Australia’s Monash University, who had hypothesized that in addition to affecting the brain, concussions would also cause alterations to the skull. This view was predicated on the knowledge that bone is a living tissue and can be shaped by mechanical forces, particularly if they are applied on a repeated basis.
To explore this idea, the team simulated mild traumatic brain injuries on rats, using a weight-drop device administered at 24-hour intervals, delivered in sets of one, two or three blows. Skull bones were collected for analysis at two weeks and again after the final round of impacts at 10 weeks, and were then imaged using micro-CT scans.
Modest increases in bone thickness were seen at two weeks, but at 10 weeks, the group receiving two impacts each day exhibited a “robust increase in the volume and thickness” of the skull bone proximal to the injury site. This was combined with a decrease in volume of marrow cavities in a region of the skull called the diploë.
"We have been ignoring the potential influence of the skull in how concussive impacts can affect the brain," said study author Associate Professor Bridgette Semple. "These new findings highlight that the skull may be an important factor that affects the consequences of repeated concussions for individuals."
The scientists are unsure whether these effects are a good thing, but note that a thicker skull is a stronger skull, at least in theory, so it may be that the altered bone has a protective effect in guarding the brain from further impacts. To explore this idea, the team is planning further studies to investigate whether a thickened skull can alter the amount of force that impacts on brain tissue in such injuries.
"This is a bit of a conundrum," Semple said. "As we know, repeated concussions can have negative consequences for brain structure and function. Regardless, concussion is never a good thing."
The research was published in the journal Scientific Reports.