Tau offers tell-tale sign of long-term TBI symptoms in military

By John Murphy, MDLinx
Published January 6, 2016

Key Takeaways

Military personnel who have multiple traumatic brain injuries (TBIs) also have elevated levels of the protein tau, researchers have found. The higher the concentration of tau in these patients, the more likely they are to have chronic symptoms of post-concussive disorder.

This finding suggests that testing tau levels in patients with TBI could predict those at highest risk for long-term symptoms. The study and an accompanying editorial appear in the August 3 issue of JAMA Neurology.

“Our findings may provide a framework for identifying patients who are most at risk for experiencing chronic symptoms related to TBI,” said lead author Jessica Gill, PhD, RN, chief of the Brain Injury Unit, Tissue Injury Branch, at the National Institute of Nursing Research (NINR), Bethesda, MD. “Identifying those at risk early in the progression of the disease provides the best opportunity for therapies that can lessen the cognitive declines that may result from these long-term effects.”

About one-third of all U.S. military personnel who served in combat operations, notably Operation Enduring Freedom and Operation Iraqi Freedom, have experienced one or more TBIs. Individuals with TBI are more likely to have ongoing complications—such as post-concussive disorder (PCD), posttraumatic stress disorder (PTSD), and depression—and are also more likely to develop chronic traumatic encephalopathy. Yet, clinicians currently have no way to identify those who are at greatest risk for developing these chronic symptoms.

In prior research on acute TBI, investigators found elevated concentrations of tau in the blood—but this was thought to return to normal levels within the months following the injury. However, no research had been done on the role of elevated tau in chronic neurological deficits long after injury or in multiple TBIs.

To that end, researchers in this study explored whether elevated levels of tau were related to chronic neurological symptoms in military personnel who had experienced TBI. A total of 70 military personnel with a history of TBI and 28 without a history of TBI were enrolled in the study. Researchers evaluated subjects for PTSD, depression, and other neurological and psychological symptoms. They also took blood samples from each participant.

The researchers used a new ultrasensitive immunoassay, which is about 1,000 times more sensitive than conventional assays in tau detection. Their findings showed that the 70 participants with TBI had significantly elevated concentrations of plasma tau compared with the 28 control participants.

The researchers also linked the physical symptoms of PCD, which can persist after TBI, to elevated levels of tau, independent of other psychological symptoms such as PTSD and depression. These findings suggest that long after the primary brain injury, tau accumulations alone may contribute to chronic neurological symptoms.

But this discovery also makes tau a potential target for therapeutic agents, the authors wrote. “This would be invaluable considering the dearth of treatments for TBIs and chronic PCD symptoms,” they concluded. 

Share with emailShare to FacebookShare to LinkedInShare to Twitter