June 16, 2015
The findings, published online in the journal Radiology, may lead the way to improved treatment and understanding of these common disorders.
Post-concussion psychiatric disorders can be extremely disabling. The mechanisms underlying these changes after a mild traumatic brain injury (TBI) are not sufficiently understood, and conventional MRI results in most of these patients are normal.
Lea M. Alhilali, MD, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, and colleagues used diffusion tensor imaging (DTI) to see if injuries to the nerves may be the root cause of these post-traumatic depression and anxiety symptoms.
The researchers obtained DTI and neurocognitive testing results for 45 patients with TBI, including 38 with irritability, 32 with depression, and 18 with anxiety, and compared the results with those of 29 patients with TBI who had no neuropsychiatric symptoms.
“Using other concussion patients as our controls was a big advantage of our study,” said Dr. Alhilali. “When you are able to study a similar population with similar risk factors, you get much more reliable results.”
The researchers saw unique white matter injury patterns in the patients who had depression or anxiety. Compared with controls, patients with depression had decreased fractional anisotropy (FA), a measure of the structural integrity of white matter connections, around an area near the deep gray matter of the brain that is strongly associated with the brain's reward circuit.
“The regions injured in concussion patients with depression were very similar to those of people with non-traumatic major depression disorder,” said Dr. Alhilali. “This suggests there may be similar mechanisms to non-trauma and trauma-dependent depression that may help guide treatment.”
Patients with anxiety had diminished FA in the vermis. Since the vermis has not been associated with dysfunction in non-traumatic anxiety disorders, this finding may indicate that different treatment targets are required for patients with anxiety after trauma, the researchers said.
No regions of significantly decreased FA were seen in patients with irritability relative to the control subjects.
“There are two major implications for this study,” said Dr. Alhilali. “First, it gives us insight into how abnormalities in the brain occur after trauma, and second, it shows that treatments for non-trauma patients with neuropsychological symptoms may be applicable to some concussion patients.”
The study also raises the possibility that some people diagnosed with non-traumatic depression may actually have experienced a subclinical traumatic event at some point earlier in their lives that may have contributed to the development of depression, she noted.
In the future, the researchers hope to compare DTI findings in concussion patients with depression with those of people who have non-trauma-related depressive disorders.
SOURCE: Radiological Society of North America