Functional correlates of diffusion tensor imaging in spinal cord injury.

Diffusion tensor magnetic resonance imaging (DTI or DT-MRI) is sensitive to the underlying neural microstructure and has been utilized to assess spinal cord integrity in various studies. The relationship between spinal cord integrity, evaluated using DTI, and functional electrophysiology remains to be determined. In this study we evaluated the relationship between characteristics of the spinal evoked potential (SpSEP) and ex vivo diffusion measurements in the medial and lateral spinothalamic tracts (STTs) and dorsal columns rostral to the lesion site. Functional electrophysiology revealed a high correlation between medial spinothalamic tract (MSTT) diffusion and the very early components (> 10 ms post-stimulus) of the SpSEP. Diffusion in the dorsal columns was highly correlation with very early components of the SpSEP up to 2 weeks post-injury, and then illustrated a significant correlation with early components (10 - 25 ms post-stimulus) after 2 weeks. Lateral spinothalamic tract (LSTT) diffusion measurements correlated significantly with the late components (25 - 100 ms post-stimulus) of the SpSEP. Results provide evidence that diffusion measurements may be able to predict electrophysiological function, illustrating the possibility of using spinal cord DTI as a functional as well as structural prognostic tool.