Bi-directional changes in fractional anisotropy are associated with altered fiber tracts after experimental TBI
Neil G Harris1, Derek R Verley2, Boris A Gutman3, and Richard L Sutton1
1Neurosurgery, UCLA, Los Angeles, CA, United States, 2Neurosurgery, University of California at Los Angeles, Los Angeles, CA, United States, 3Engineering, Radiology, & Ophthalmology, University of Southern California, Los Angeles, CA, United States
Diffusion tensor imaging (DTI) is
now widely used in both clinical and experimental research for studying pathology
related to traumatic brain injury. However, studies report a wide range of DTI
indices that are not easily ascribed to post-injury time-point, injury severity
or developmental stage. In order to provide further information to help interpret
these often complex changes we obtained DTI data before and after TBI using the
well-known, clinically relevant rodent controlled cortical impact (CCI) model
of TBI. In addition to the expected decreases in fractional anisotropy (FA) around
the primary injury site which were associated with myelin breakdown and
neurofilament loss, we found significant increases in FA within subcortical
regions that were not associated with gliosis or fiber tract degeneration. Fiber tract density was decreased
in regions of lowered FA but significantly increased only in subcortical
regions associated with increased FA. High FA region seeded for tractography
yielded significantly increased fiber length compared to pre-injury. These data
provide additional insight into the interpretation of DTI indices following
TBI.
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