Ependymal Glia

Ependymal glia, columnar or cuboidal ciliated epithelial cells, line the surface of the ventricles and the spinal canal (Fig. 2.8). They react to a variety of pathologic insults.

Pathology

The pathology of ependymal glia is summarized in Table 2.5.

Atrophy, tearing, and discontinuity commonly occur in chronic hydrocephalus. Ependymitis, caused by a variety of pathogens, consists of necrosis, breaking up of the ependymal lining, and subependymal inflammatory infiltrations.

Subependymal gliosis, or granular ependymitis, develops in syphilitic and various other infectious, toxic, metabolic, and vascular diseases. Grossly, tiny nodules from the ventricular surface project into the lumen. Histologically, these nodules are proliferated subepen-dymal fibrillary astrocytes. Some are covered with continuous or disrupted ependymal layer and others are denuded. Occasionally, these nodules may enlarge enough to obstruct the aqueduct of Sylvius and cause hydrocephalus (see Fig. 2.8).

Nuclear and cytoplasmic viral inclusions in enlarged ependymal cells are characteristic of cytomegalovirus infection.

Neoplastic Transformation

Ependymal cells are capable of proliferating into neoplasms that may grow into the parenchyma or project into the ventricle.

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FIGURE 2.9

Microglia. A. Resting microglia showing small elongated nucleus, scanty cytoplasm, and bipolar processes (Hortega silver stain). B. Activated rod-shaped microglia in encephalitis. C. Macrophages showing large, round, foamy cytoplasms and small eccentric nuclei (HE).

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