The brain's emotional control center is larger in individuals who develop post-traumatic stress disorder (PTSD) after mild traumatic brain injury (mTBI) than in those with mTBI who don't develop PTSD, researchers have observed.
"Many consider PTSD to be a psychological disorder, but our study found a key physical difference in the brains of military-trained individuals with brain injury and PTSD, specifically the size of the right amygdala," Joel Pieper, MD, from University of California, San Diego, said in a news release.
The study was presented July 15 at the American Academy of Neurology (AAN) 2017 Sports Concussion Conference in Jacksonville, Florida.
The study included 89 current or former members of the military with mTBI. According to standard symptom scale ratings, 29 had significant PTSD in addition to mTBI, while the remaining 60 had mTBI without PTSD. Age, education, and sex did not significantly differ between the two groups.
Individuals with mTBI and PTSD had 6% overall larger amygdala volumes when normalized to intracranial volume, particularly on the right side, compared with those with mTBI only. Non-normalized amygdala volumes showed no significant between-group difference.
"This study shows a structural change in the brain associated with PTSD in head injury subjects," coauthor Douglas Chang, MD, PhD, professor and chief of Physical Medicine and Rehabilitation Service at UC San Diego Health in California, told Medscape Medical News.
"It's really interesting why we might see these results," he added. "Are there susceptible individuals prone to PTSD symptoms after a head injury, with a larger amygdala to begin with, so that they have a brain primed to respond to fear and startle reflexes in an exaggerated fashion? Or are these physical changes a result of neuroplasticity, of a brain reaction to fear conditions resulting in growth of the neural networks of the amygdala fear processing organ?"
"We wonder," said Dr Chang, "if amygdala size could be used to screen who is most at risk to develop PTSD symptoms after a head injury. On the other hand, if there are environmental or psychological cues that lead to neuroplasticity and enlargement of the amygdala, then maybe such influences can be followed with MRI scans and used to develop treatment interventions."
The researchers say further studies are needed to better define the relationship between amygdala size and PTSD in mTBI. It also remains to be seen whether similar results may be found in those with sports-related concussions, as opposed to blast injuries.
A Neuropsychiatric Condition
"This is an interesting study that combines PTSD research with mild TBI research. It is increasingly known that mild TBI is a risk factor for the development of PTSD. What is notable here is the finding of increased amygdala volume in patients with PTSD and mild TBI in comparison to people with mild TBI and without PTSD symptoms," David L. Perez, MD, MMSc, Massachusetts General Hospital in Boston, told Medscape Medical News.
"This finding builds upon the literature in PTSD showing both structural and functional changes in the amygdala, including commonly described increased amygdalar activation. The results on the volumetric side have been mixed in the literature, although there have been some studies showing increased amygdala volume in patients with PTSD," said Dr Perez.
"As a dual-trained neurologist and psychiatrist, I think about PTSD as a neuropsychiatric condition. This is clearly a brain-based condition, and I think the field is moving in that direction both to understand the biology of PTSD itself and to understand the interplay of disorders that may increase disease risk or somehow change the trajectory of patients who go on to develop PTSD. One of those interesting intersections is the intersection of mild TBI and PTSD," he added.
The study was supported by the Department of Veterans Affairs and Naval Medical Research Center's Advanced Medical Development program. The authors have disclosed no relevant financial relationships.
American Academy of Neurology (AAN) 2017 Sports Concussion Conference. Presented July 15, 2017.
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Cite this: PTSD May Be Physical, Not Just Psychological - Medscape - Jul 21, 2017.