FIG. 1.

Histopathology of representative dogs with acute (0–3 days) (A–C), subacute (3 days–3 weeks) (D–F), and chronic (>3 weeks) (G–I) spinal cord injury (SCI) because of intervertebral disk herniation (IVDH). (A) Overview of a case of acute SCI, demonstrating relatively preserved morphology. Several swollen axons within moderately dilated myelin sheaths are observed throughout the white matter, accompanied by mild to moderate gray matter hemorrhage. (B) Closer view of extravasated erythrocytes (hemorrhage) in close proximity to the central canal. Some axons appear hypereosinophilic and swollen (spheroids); 10 × objective. (C) Axonal damage is a consistent feature of IVDE-induced SCI, as demonstrated by intense axonal immunoreactivity for nonphosphorylated neurofilament (arrows); 20 × objective. (D) Overview of a case of subacute SCI, demonstrating preserved architecture but diffuse pallor of the white matter, indicating myelin sheath edema and swelling. (E) Within dilated myelin sheaths, which are commonly affected by axonal dropout, phagocytic cells with foamy, vacuolated cytoplasm and excentric nuclei are commonly observed (arrow), indicating myelino- and axonophagia; 40 × objective. (F) Cells intensely labeled by a lectin of Bandeiraea simplicifolia (arrows) are indicative of the microglia/macrophage origin of these cells; 40 × objective. (G) Overview of a case with chronic SCI with severe destruction of the organotypic architecture of white matter (open asterisk) and gray matter (asterisk). There is necrosis (myelomalacia) as well as glial scarring, which predominantly affects the gray matter. Note degenerated intervertebral disk material, which is attached to the dura mater in this case (arrow) (H) Closer view of the white (open asterisk) and gray matter (asterisk) of the same case. While there is intense diffuse hyperemia of blood vessels, the gray matter is characterized by severe proliferation of partly spindloid glial cells and capillaries, consistent with glial scar tissue formation; 10 × objective. (I) White matter (open asterisk) and gray matter (asterisk) of another case with chronic SCI. Besides myelin sheath swelling, the white matter is relatively preserved, while there is severe diffuse infiltration of myriads of phagocytic macrophages within the gray matter, as demonstrated by positivity with the lectin of Bandeiraea simplicifolia, indicating severe necrosis of the gray matter; 20 × objective. Hematoxylin and eosin staining (A, B, D, E, G, H) and immuno-(C) and lectin histochemistry (F, I) using the avidin-biotin-peroxidase complex method and 3,3′-diaminobenzidine as chromogen.