Endogenous recovery of injured spinal cord: longitudinal in vivo magnetic resonance imaging.

Pathological changes were followed longitudinally with in vivo magnetic resonance imaging (MRI) and behavioral studies in experimental spinal cord injury (SCI). MRI-observed pathology was correlated with histology. On MRI, the cavitated regions of the injured cord were gradually filled with viable tissue between two and 8 weeks postinjury, and a concomitant improvement was observed in the neurobehavioral scores. By weeks 3-6, on MRI, the gray matter (GM) returned in the segments caudal, but not rostral, to the injury site. The corresponding histological sections revealed motor neurons as well as other nuclei in the gray matter immediately caudal to the epicenter, but not at the site of injury, suggesting neuronal recovery in perilesioned areas. The neuronal and neurological recovery appeared to occur about the same time as neovasculature that was reported on the contrast-enhanced MRI, suggesting a role for angiogenesis in recovery from SCI. The role of angiogenesis in neuronal recovery is further supported by the immunohistochemical observation of greater bromodeoxyuridine uptake by blood vessels near the lesion site compared with uninjured cords.