Introduction: The objective of this study was to prospectively explore the temporal changes of the apparent diffusion coefficient (ADC) values in the corpus callosum of TBI patients throughout the first year and relate the findings to outcome and neuropsychological function.
Methods: Sixty patients (mean age 33.2, range 11-64 years) were examined with diffusion MRI at three time points (median 8 days, 3 and 12 months) during the first year post-injury, and a control group of 47 healthy individuals matched on age and sex were examined once. For both patients and controls, the corpus callosum was subdivided into five regions (Hofer & Frahm scheme) and the mean ADC-values computed in 10 regions of interests (ROIs) without any visible lesions. This was done blinded for clinical information. Glasgow Outcome Scale Extended (GOSE) and neuropsychological function were assessed at 12 months post-injury.
Results: We found no differences in the ADC-values between the early and 3 months MRI, but a significant increase of the ADC-values in the posterior truncal parts at 12 months (p=0.025) post-injury. Compared with the controls, we found no significant differences of the ADC-values in the early MRI, but increased ADC-values in both the genu (p=0.024) and truncal (p=0.001-0.027) parts of the corpus callosum at 12 months MRI. The ADC-values in the chronic phase showed no association with GOSE, but the increased ADC-values in the posterior truncal parts correlated negatively with motor score in neuropsychological tests (r=-0.29, p=0.049), and regression analyses with adjustment for age showed the same tendency (p=0.058).
Conclusions: In this study we have demonstrated damage to the microstructure of the genu and truncal parts of normal appearing corpus callosum on diffusion weighted MRI, first detectable in the chronic stages following TBI. The degree of injury in the truncal parts was negatively associated with motor function post-injury.
Patient Care: The detection of injury to areas in the brain without any visible lesion, may explain patient outcome and reduced function post-injury.
Learning Objectives: By the conclusion of this session, participants should: 1) understand that corpus callosum without visible lesions in conventional MRI still have signs of injury to the microstructure and 2)the degree of this injury is related to neuropsychological function post-injury.