Page:Acute Poliomyelitis.djvu/39

PATHOLOGICAL ANATOMY 27 tissue and the neural reticulum are replaced by a granular substance, which is intersected, as by coarse threads, by processes of newly formed glial cells. Not even debris of the nerve elements may be detectable in these severely affected areas (Plate II, Fig. 10).

The small cell elements do not behave in this as in the acute stage. Besides the granular, typical Unna-Marschalko plasma, and distinctly proliferating glia, cells are present in great numbers. Spindles and other derivatives of the adventitial cells occur. Later, the granular cells gradually retreat till they are chiefly restricted to the lymph sheath of the vessels, where they may occasionally remain, even as long as two years after the onset of the disease (Roger and Damaschino, Lovegren). The neuroglia becomes more distinct and its cells develop so many wide and much branched processes that they resemble seaweed-covered stones. These processes gather together and the neuroglia loses its normal delicate felt-like appearance. The change advances. Naturally, the appearances observed in cicatrization depend upon the extent and severity of the destruction in the acute stage. If the entire anterior horn were then implicated to a degree which resulted in complete destruction, it would now appear atrophied even to the naked eye; and on microscopic examination, only neuroglia would be seen. In some cases such definite gliosis is present only in limited foci and normal areas still persist in the anterior horn. But if the destruction during the acute stage were not so intense, a more or less marked thickening of the neuroglia with rarefaction and atrophy of the nerve elements ensues. Obviously all possible degrees of transition between these various conditions may occur.

The changes in the ganglion cells originally reported by Prevost and Vulpian were later confirmed by Lockhart, Clarke, Charcot, Joffroy and subsequent investigators. It was observed in some cases that ganglion cells were affected in groups (Sahli, Dejerine and Huet). But within the affected groups, isolated normal ganglion cells still persisted in varying number at different levels of the cord. In one case Lovegren noticed that the boundary of an inflammatory focus ran across a ganglion cell group. Kawka, Goldscheider and Kohnstamm were able to demonstrate that the sclerosed areas are associated with thickened vessels. Groups of