A recent study was published looking into whether brain changes were evident after only a handful of repeated subconcussive impacts finding the answer is yes.
In the recent study, titled Repetitive sub-concussive impacts induce inflammation implications for innocuous head impacts in sports, the authors conducted a series of experiments on rats. They designed a device to cause sub concussive impacts. In one group of rats no impacts were received. In a second group only one impact was received. In the last group 10 consecutive impacts were received. After “sacrifice” the brains of the rats were microscopically examined. The researchers found neuropathological changes in the third group of mice as compared to the control groups.
The study’s abstract reads as follows:
A sub-concussive impact is defined by Center for Diseases Control as a bump, blow or jolt to the head not resulting in any apparent symptoms. The current effort was conducted to determine the effects seen in repetitive sub-concussive impacts in comparison to a single sub-concussive impact. This pilot study attempts to assess the neuropathological changes in rats subjected to repetitive sub-concussive impacts. Nine Sprague Dawley rats were divided into three different groups (n=3 each): sham, sub-concussive (SC) and repetitive sub-concussive (RSC). They were subjected to SC or RSC using a modified Marmarou impact acceleration injury model under anesthesia. SC or RSC impacts consisted of dropping a 50-gram brass weight from a height of 40 cm onto a metal disc (helmet) taped to the scalp. The animals were sacrificed 7 days post-impact, and their brains were perfused with 4% paraformaldehyde. Representative sections encompassing the hippocampus were processed by immunohistochemistry for assessing microglial and astrocytic proliferation changes using IBA (Ionized Calcium-binding Adaptor molecule) as the marker. Four sections from each brain 500 microns apart were taken from the left and right sides of each section encompassing the CA1 region of the hippocampus. Our results support that RSC induced a significant increase in microglial proliferation compared to SC and sham animal groups (p< 0.05).