Military mild TBI outcomes vary considerably, study finds

Long-term outcomes for combat veterans and service members with mild TBI (traumatic brain injury) vary widely, a 10-year study has found.

While most people with mild TBI had a sustained recovery, some saw symptoms worsen over time.

The findings could help identify those at high risk of later psychological, neurobehavioural or cognitive problems before they appear.

Lead researcher Christine MacDonald, a professor of neurosurgery at the University of Washington School of Medicine in Seattle.

She said: “We found that service members who had mild traumatic brain injury fell into different TBI subtypes, with many showing resilience but important subgroups at risk for later decline.”

Researchers followed 288 service members from deployment in Iraq and Afghanistan to 10 years later, with evaluations at one, five and 10 years.

Each visit included an MRI scan and assessments of 34 psychological, cognitive and neurological/neurobehavioural functions.

Two combat-related mild TBI groups were examined: 137 after blast exposure and 21 after blunt trauma.

For comparison, two control groups without a history of TBI were also evaluated, including 36 with blast exposure and 94 without.

Using the clinical outcome data, the authors found four clusters or subtypes. One group was designated resilient, with no significant cognitive dysfunction or neurobehavioural or psychological symptoms after 10 years. W

hile most in this subtype were controls, 36 per cent were service members with mild TBI.

The other three subtypes included those with mild, moderate or severe symptoms. Notably, these profile subtypes did not emerge with full clarity until the last of the three clinical evaluations.

MRI scans also detected differences in the volume of some brain structures, such as the cerebellum and brainstem, which are involved in learning and emotion.

Unlike clinical outcomes, brain imaging differences by subtype were detected in the earliest MRI scans.

MacDonald said: “We identified evolving clinical outcomes in service members which could allow for stratification into focused intervention strategies years before they start to notably decline, essentially flipping treatment concepts on their head and being proactive instead of reactive.”