Cortical thinning in patients with recent onset post-traumatic stress disorder after a single prolonged trauma exposure

Abstract

Most of magnetic resonance imaging (MRI) studies about post-traumatic stress disorder (PTSD) focused primarily on measuring of small brain structure volume or regional brain volume changes. There were rare reports investigating cortical thickness alterations in recent onset PTSD. Recent advances in computational analysis made it possible to measure cortical thickness in a fully automatic way, along with voxel-based morphometry (VBM) that enables an exploration of global structural changes throughout the brain by applying statistical parametric mapping (SPM) to high-resolution MRI. In this paper, Laplacian method was utilized to estimate cortical thickness after automatic segmentation of gray matter from MR images under SPM. Then thickness maps were analyzed by SPM8. Comparison between 10 survivors from a mining disaster with recent onset PTSD and 10 survivors without PTSD from the same trauma indicates cortical thinning in the left parietal lobe, right inferior frontal gyrus, and right parahippocampal gyrus. The regional cortical thickness of the right inferior frontal gyrus showed a significant negative correlation with the CAPS score in the patients with PTSD. Our study suggests that shape-related cortical thickness analysis may be more sensitive than volumetric analysis to subtle alteration at early stage of PTSD.

Figure 1. Two-dimensional example of Laplacian method.

The Laplace's equation is solved between S and S′, which have predetermined boundary conditions of 1 V and 0 V, respectively (as in an electric field). The length of the streamlines between the two surfaces then defines the thickness.

Figure 2. Regional cortical thinning in recent onset PTSD patients versus trauma survivors without PTSD.

Regional cortical thinning in the following areas were rendered onto orthogonal slices: (a) left parietal lobe; (b) right inferior frontal gyrus; (c) right parahippocampal gyrus. L, left hemisphere; R, right hemisphere. PTSD, post-traumatic stress disorder.

Figure 3. Mean cortical thickness of the right inferior frontal gyrus correlations with the CAPS score of PTSD patients.

PTSD, post-traumatic stress disorder. r, Pearson's correlation coefficient; p, p value.