To identify amygdalar volumetric differences associated with posttraumatic
stress disorder (PTSD) in individuals with comorbid mild traumatic
brain injury (mTBI) compared with those with mTBI-only and to examine the effects of intracranial volume (ICV) on amygdala
Marine Corps Base and VA Healthcare System.
A cohort of veterans and active-duty military personnel with combat-related mTBI (N
Twenty-nine participants were identified with comorbid PTSD and mTBI. The remaining 60 formed the mTBI-only control group. Structural images of brains were obtained with a 1.5-T MRI scanner using a T1-weighted 3D-IR-FSPGR pulse sequence. Automatic segmentation was performed in Freesurfer.
Main Measures: Amygdala
volumes with/without normalizations to ICV.
The comorbid mTBI/PTSD group had significantly larger amygdala
volumes, when normalized to ICV, compared with the mTBI-only group. The right and left amygdala
volumes after normalization to ICV were 0.122% ± 0.012% and 0.118% ± 0.011%, respectively, in the comorbid group compared with 0.115% ± 0.012% and 0.112% ± 0.009%, respectively, in the mTBI-only group (corrected P
The ICV normalization analysis performed here may resolve previous literature discrepancies. This is an intriguing structural finding, given the role of the amygdala
in the challenging neuroemotive symptoms witnessed in casualties of combat-related mTBI and PTSD.