Diagnostic determination by diffusion tensor imaging of neural axon injury between the 2 hemispheres following traumatic brain injury

Abstract

Traumatic brain injury (TBI) is caused by an external mechanical force to the head resulting in alteration of brain function. However, the injury to neural tracts and the connections between them is difficult to diagnose using traditional imaging techniques. A 54-year-old woman visited our clinic because of insufficient coordination of her body. Her personal history included severe TBI with a 10-day coma medically treated 10 years previously. She presented with memory impairment and insufficient coordination of her body, suggesting post-concussion syndrome. Her Glasgow Coma Scale score was 15 and the strength testing result was 5/5 for both sides; however, she could not walk. She had been examined at many medical centers, but without a diagnosis of her condition. She was scanned using morphometric magnetic resonance imaging (MRI), which detected a significant reduction in the corpus callosum. MRI-diffusion tensor imaging (DTI) revealed decreased fractional anisotropy (FA) in the white matter of the right temporal lobe and the corpus callosum. FA reflects the degree of anisotropy of water molecules. The decrease in FA in the corpus callosum indicated loss of connection between the 2 hemispheres. MRI tractography was used to describe the number of neural tracts in the corpus callosum. MRI-DTI and MRI tractography served as powerful diagnostic tools, providing imaging results that offered an explanation for our patient's clinical picture.

Keywords: Cerebral atrophy; Diffusion tensor imaging; Morphometry; Tractography; Trauma brain injury.

Fig. 1

(A-D) show the old brain lesion in the right temporal lobe, hyperintensity on T2W, and hypointensity on T1W and FLAIR–DWI (orange arrow). (E-G) show normal cerebral signal intensity on MRI. (H) is the sagittal T1W image of the corpus callosum showing a reduction in its size (blue arrow).

Fig. 2

Fractional anisotropy (FA) map of the corpus callosum. (A, C, D, and E) show FA measurements of parts of the corpus callosum. (B) shows the results of correlation between the positions of the regions of interest (ROIs).

Fig. 3

Right (R) and left (L) neuron tracts visualized by tractography. (A-C) show the axial, sagittal, and coronal views, respectively, of the neuron tracts in the corpus callosum. (D and E) are 3D images of axon bundles showing the lack of neuron fibers in the corpus callosum.