Diffusion tensor imaging characteristics of the corpus callosum in mild, moderate, and severe traumatic brain injury

Abstract

Background and purpose: The corpus callosum is an important predilection site for traumatic axonal injury but may be unevenly affected in head trauma. We hypothesized that there were local differences in axonal injury within the corpus callosum as investigated with diffusion tensor imaging (DTI), varying among patients with differing severity of traumatic brain injury (TBI).

Materials and methods: Ethics committee approval and informed consent were obtained. Ten control subjects (7 men, 3 women; mean age, 37 +/- 9 years) and 39 patients with TBI (27 men, 12 women; 34 +/- 12 years) were investigated, of whom 24 had mild; 9, moderate; and 6, severe TBI. Regions of interest were selected in the callosal genu, body, and splenium to calculate fractional anisotropy (FA), apparent diffusion coefficient (ADC), and the number of fibers passing through. Statistical comparison was made through analysis of variance with the Scheffé post hoc analysis.

Results: Compared with controls, patients with mild TBI investigated <3 months posttrauma (n = 12) had reduced FA (P < .01) and increased ADC (P < .05) in the genu, whereas patients with mild TBI investigated > or =3 months posttrauma (n = 12) showed no significant differences. Patients with moderate and severe TBI, all investigated <3 months posttrauma, had reduced FA (P < .001) and increased ADC (P < .01) in the genu compared with controls and reduced FA in the splenium (P < .001) without significant ADC change.

Conclusion: Mild TBI is associated with DTI abnormalities in the genu <3 months posttrauma. In more severe TBI, both the genu and splenium are affected. DTI suggests a larger contribution of vasogenic edema in the genu than in the splenium in TBI.

Fig 1.

Localization of regions of interest. The upper row of images shows axial color-coded maps of FA with region-of-interest localization in the genu (left image), body (middle image), and splenium (right image) of the corpus callosum. Regions of interest are shown in white. The lower row of images shows the corresponding axial FLAIR scans.

Fig 2.

Regions of interest with reconstructed fibers in a patient with mild TBI. Regions of interest and fibers are superimposed on T2-weighted images. The upper 2 images show a lateral view with typical region-of-interest localization in the genu, body, and splenium without (left upper image) and with (right upper image) reconstructed fibers passing through. The lower images show the same regions of interest and reconstructed fibers in the anterior oblique view.