Longitudinal analysis of brain diffusion tensor imaging in patients with moderate and severe traumatic diffuse axonal injury

Author(s)

Daphine Cêntola Grassi

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2021-06-25

Examining board members

Celi Santos Andrade; Leandro Tavares Lucato; Kette Dualibi Ramos Valente

• Advisor: Celi Santos Andrade

Abstract

Introduction: Currently, traumatic brain injury (TBI) is a worldwide public health problem due to its high prevalence, morbidity, and mortality. The mechanisms involved in trauma are complex, and different types of injuries may be present, including diffuse axonal injury (DAI). DAI is highly prevalent in victims of moderate and severe trauma, being responsible for most individuals who are in a vegetative state or with severe loss of ability after injury. It involves different and prolonged pathophysiological processes which lead to neurodegeneration. Objective: To evaluate longitudinally using diffusion tensor imaging (DTI) the integrity of the cerebral white matter in patients with moderate and severe DAI at three moments after trauma, and in comparison with healthy control subjects. In addition, we aimed to test correlations between the DTI parameters and patients\' neuropsychological data. Methods: Twenty victims of moderate and severe TBI and 20 controls, matched for age and sex, were selected. MRI exam was performed at three different times: 2 months (time 1), 6 months (time 2) and 12 months (time 3) of the TBI. In the control group, the MR examination was performed in a single moment. We evaluated the superior longitudinal fascicle and the corpus callosum with tractography analysis, as well as the the whole brain with voxelwise analysis to extract DTI quantitative parameters. In addition, different cognitive domains were tested, and patients\' clinical outcome was assessed one year after trauma. Correlation tests were performed using the DTI parameters with the cognitive domains examined. Results with p < 0.05 were considered significant. Results: The patients group had lower mean FA values and higher mean MD values in all sites when compared to the control group. Voxelwise analysis indicated significant changes over time in DTI parameters in the patients group. We observed improvements in patients\' attention and memory. We identified different correlations between the DTI parameters and the different cognitive functions over time. Discussion and Conclusions: We observed quantitative changes in the DTI values in the studied segments. FA is related to axonal integrity and reduced values are present in states of loss of white matter cohesion. Moreover, high MD values may be related to the loss of the microstructural organization of neuronal tissues. The various correlations between cognitive indexes and DTI parameters in different brain areas demonstrate how heterogeneous and extensive the microstructural changes are present in trauma victims. Changes in the correlations over time confirms the dynamic and prolonged nature of the biological mechanisms involved in DAI. The results of this study demonstrate that even after 12 months of the traumatic event, there are microstructural changes in the white matter, and these are detectable by DTI. We believe that, in the future, the quantitative parameters of DTI may be useful as biomarkers in estimating the severity of the injury and guiding rehabilitation process (AU)

• FAPESP's process: 17/17065-9 - Longitudinal analysis of diffusion tensor imaging of the brain in patients with moderate to severe traumatic diffuse axonal injury
• Grantee: Daphine Centola Grassi
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)