Introduction: The objective of this study was to examine non-hemorrhagic traumatic axonal injury (TAI) / diffuse axonal injury lesions depicted in conventional MRI in early and chronic phases, and compare persisting versus non-persisting TAI-lesions with diffusion tensor imaging (DTI) findings indicating the degree of axonal microstructural integrity (measured by fractional anisotropy, FA).
Methods: Thirty-eight patients (mean age 24.7, range 13-63 years) with moderate to severe traumatic brain injury (TBI) were admitted to St.Olav University Hospital in Trondheim, Norway. All underwent MRI including fluid-attenuated inversion recovery (FLAIR) in the early phase (median 7 days) and FLAIR, T1 and DTI in the chronic phase (1-5 years). The non-hemorrhagic TAI lesions were characterized based on location (hemispheres, corpus callosum, brain stem and thalamus/basal ganglia) in the early FLAIR images. The FLAIR images were linearly registered to the FA images via T1-weighted images (FSL), and the lesions were manually segmented on the FA-registered FLAIR images. Mean FA was calculated for each lesion. FA values below 0.15 were excluded.
Results: In the early FLAIR images, 25 of the 38 TBI patients had lesions, and a total of 63 lesions were followed longitudinally. In the chronic FLAIR sequence, 48 of the lesions had attenuated. We found no difference in mean FA between the persisting and non-persisting lesions (p=0.45). Subanalyses based on location showed no difference between the two types of lesions, except for corpus callosum with a tendency towards reduced mean FA for those with persisting lesions (p=0.079). However, logistic regressions with adjustment for age and sex revealed no differences in mean FA.
Conclusions: Few non-hemorrhagic TAI lesions depicted in early conventional MRI persist as visible gliotic lesions into the chronic stages. This study could not demonstrate any higher degree of microstructural damage in the persisting compared to the non-persisting lesions.
Patient Care: Knowledge on how the different lesions develop over time and the degree of damage to the microstructure of the different types of lesions could indicate an important prognostic value.
Learning Objectives: By the conclusion of this session participants should understand that few non-hemorrhagic lesions persist into the chronic stages, and that our study could not find any differences in microstructural damage between different non-hemorrhagic lesion areas depicted in early MRI.