Examining The Effects Of Mild Traumatic Brain Injury On Brainstem Integrity

Abstract

Concussion-related brainstem injuries have received little attention in research, yet concussion-related symptoms, e.g. headache and postural instability, share a common neurological origin within the brainstem. As advanced neuroimaging techniques evolve, so do opportunities to better examine the underlying damage in the brainstem and its related white matter (WM) circuitry following an mTBI. PURPOSE: To examine the brainstem integrity in mTBI patients using advanced neuroimaging techniques. METHODS: T1-weighted and diffiusion-weighted MRI scans were performed on 13 mTBI participants within 14 days of their injuries and 3 individuals without history of brain injury. Diffusion images were acquired using a multishell high-definition fiber tracking sequence. The data were reconstructed using generalized q-sampling imaging, then a deterministic fiber tracking algorithm was applied to generate WM tract profiles indicating the quantitative anisotropy (QA) for the bilateral frontal, parietal, and occipital corticopontine tracts (CPT), the corticospinal tracts (CST), the corticoreticular tracts (CRT), and the middle cerebellar peduncle (MCP). Volumes of the midbrain, pons, medulla oblongata, and superior cerebellar peduncle were determined using Freesurfer v6. A two-sample t-test was used to determine between-group differences in the segmented brainstem structures. One-dimensional statistical parametric mapping was performed to compare WM tracts, and Hedge’s g was calculated to determine between-group effect size.RESULTS: QA values for the first 5% (caudal end) of the left CPT-F was significantly lower in the mTBI group (p = .021). Large effect sizes were found when comparing mTBI to control groups for overall tract QA for the right CPT-O and CPT-F, left and right CPT-P, CST, CRT, and MCP (g > 0.8), with the largest effect for the left CPT-F tract (g = 1.64). There were no significant differences between groups in the segmented brainstem volumes. CONCLUSION: Lower QA values in the caudal portion of the CPT-F indicate that WM near the brainstem may be susceptible to mTBI-related change despite a lack of effect on brainstem volume. Further research should investigate the brainstem after mTBI. Supported by NIH Grant R21 12973518