MR imaging and differentiation of cerebral fat embolism syndrome from diffuse axonal injury: application of diffusion tensor imaging.

INTRODUCTION: Cerebral fat embolism syndrome (CFES) mimics diffuse axonal injury (DAI) on MRI with vasogenic edema, cytotoxic edema, and micro-hemorrhages, making specific diagnosis a challenge. The objective of our study is to determine and compare the diagnostic utility of the conventional MRI and DTI in differentiating cerebral fat embolism syndrome from diffuse axonal injury. METHODS: This retrospective study was performed after recruiting 11 patients with severe CFES and ten patients with severe DAI. Three trauma radiologists analyzed conventional MR images to determine the presence or absence of CFES and DAI. DTI analysis of the whole-brain white matter was performed to obtain the directional diffusivities. The results were correlated with clinical diagnosis to determine the diagnostic utility of conventional MRI and DTI. RESULTS: The sensitivity, specificity, and accuracy of conventional MRI in diagnosing CFES, obtained from the pooled data were 76, 85, and 80 %, respectively. Mean radial diffusivity (RD) was significantly higher and the mean fractional anisotropy (FA) was lower in CFES and differentiated subjects with CFES from the DAI group. Area under the receiver operating characteristic (ROC) curve for conventional MRI was 0.82, and for the differentiating DTI parameters the values were 0.75 (RD) and 0.86 (FA), respectively. CONCLUSIONS: There is no significant difference between diagnostic performance of DTI and conventional MRI in CFES, but a difference in directional diffusivities was clearly identified between CFES and DAI.

Diagnosis of traumatic optic neuropathy: application of diffusion tensor magnetic resonance imaging.

BACKGROUND: Using diffusion tensor imaging, we evaluated the directional diffusivities of the optic nerve in patients with traumatic optic neuropathy (TON). METHODS: Our study consisted of 12 patients with unilateral TON, 6 patients with severe traumatic brain injury (comparison group A), and 6 patients with normal conventional brain magnetic resonance imaging (comparison group B). The contralateral optic nerve in patients with TON also was evaluated (comparison group C). Two trauma radiologists, blinded to the clinical diagnosis, independently obtained the directional diffusivities. The intraorbital optic nerve was divided into anterior and posterior segments to evaluate intersegmental differences in directional diffusivities. RESULTS: The mean axial diffusivity (AD) in both optic nerve segments and the mean diffusivity (ADC) in the posterior segment on the affected side were significantly lower and differentiated subjects with TON from those in comparison groups A and B. Area under the receiver operating characteristic curve was 0.762, 0.746, and 0.737 for posterior AD, anterior AD, and posterior ADC, respectively. The mean AD, mean diffusivity, and radial diffusivity were lower in the affected nerves in comparison to the contralateral nerve (comparison group C), but the values did not reach statistical significance. CONCLUSION: Decreased AD and mean diffusivity in the posterior segment of the optic nerve may serve as a biomarker of axonal damage in patients with TON and merits further investigation as a predictor of initial visual acuity and potential visual recovery.