Fig. 4. Three-dimensional reconstruction of a control spinal cord segment. (Ai) A three-dimensional reconstruction of an entire 4.2 mm long spinal cord segment fenestrated by cysts. This image displays both normal and damaged spinal cord tissue with the cysts removed. One can see through this image because cystic cavitations transverse the width of the cord. Cysts can also be seen at the rostral end of the segment as pockets or invaginations at the end of the reconstructed spinal segment where these spaces (filled with fluid in situ) have extended beyond the boundary of the segment sectioned (refer to Fig. 2A). In Bi and Ci, only the undamaged parenchyma has been reconstructed. Aii shows cavitated and hemorrhagic gray matter inundated with macrophages (large circular cells in the center of the image). Bii shows a low-power photomicrograph of a region of partial sparing at the boundary of gray and white matter. Note the three well-stained neurons. Subpial sparing of white matter axons is shown in Cii. Note the orientation in Bi. In Ci, the spinal segment was rotated by approximately 200° in the horizontal plane. These reconstructions emphasize that intact parenchyma was mostly restricted to the periphery of the injured spinal segment and show the absence of contiguous gray and white matter through the lesion. The cylindrical icon gives the relative orientation of the three-dimensional segment; gray is the rostral end and black is the caudal end. Scale bars, 1 mm.