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Within 2 weeks of their injury, all patients had diffusion tensor imaging (DTI) to assess the function of the axons, bundles of nerve fiber in the brain's white matter. DTI captures the direction of movement of water molecules along those nerve bundles -- fractional anisotropy -- which in healthy white matter is highly uniform, but after injury is typically less so.

However, Lipton said, studies have also shown instances of extremely high uniform movement of water molecules after injury -- a phenomenon known as abnormally high FA -- although it hasn't been clear why this occurs.