Longitudinal changes in diffusion tensor imaging parameters of the corpus callosum between 6 and 12 months after diffuse axonal injury

ABSTRACT

Background: Magnetic resonance diffusion tensor imaging (MR-DTI) is used increasingly to detect diffuse axonal injury (DAI) after traumatic brain injury (TBI).

Primary objective: To investigate changes in the diffusion tensor imaging parameters of the corpus callosum 6 and 12 months after TBI, to optimize the timing of follow-up DTI investigations. A secondary goal was to study the relationship between DTI parameters and outcome.

Research design: Longitudinal prospective study.

Methods and procedures: MR-DTI was performed in 15 patients with suspected DAI, 6 and 12 months post-injury. Sixteen controls were also examined. Fractional anisotropy (FA) and diffusivity (trace) in the corpus callosum were analysed. The outcome measures were the extended Glasgow Outcome Scale and the Barrow Neurological Institute Screen for Higher Cerebral Functions, assessed at 6 and 12 months.

Main outcomes and results: FA decreased and trace increased at 6 and 12 months compared to controls. Trace continued to increase even further between 6 and 12 months, while FA remained unchanged. Patients with the worst outcomes had lower FA and higher trace compared to patients with better outcomes.

Conclusions: DTI parameters have not reached a stable level at 6 months after DAI, but continue to change, probably reflecting an incessant microstructural alteration of the white matter.

KEYWORDS:

• Traumatic brain injury
• axonal injury
• MRI
• outcome measures

Acknowledgements

We would like to thank Nils-Gunnar Pehrsson and Anton Mårtensson for their support in the statistical analysis.

Declaration of interest

The authors report no conflicts of interest. This work was supported by grants from the Health and Medical Care Committee of Västra Götaland, and the Foundation for Medical Imaging in Memory of Erik Lysholm.