[Study of isolated nerve fibers in primary hypertrophic neuritis].

This report describes pathological changes of myelin, cells and axons of teased nerve fibers from three cases (two having a family history) of primary hypertrophic neuritis with onion bulb formations seen in aptic and electron microscopy. Segmental demyelination and subsequent remyelination occurred in most myelinated fibers isolated. Besides this classical pattern, in some fibers large pseudo-wallerian ovoids of myelin with preservation of the axon, demonstrated by silver counterstaining, were found. This pseudo-wallerian degeneration is thus a primary demyelination and axonal degeneration remains a rare finding. A quantitative evaluation of the different patterns of myelin degeneration has been established. The study of cellular proliferation has shown clustering of nuclei scattered along the fiber. In some fibers the changes of the myelin sheath are encountered without Schwann-cell accummulation, while in others cellular proliferation is prominent without obvious myelin abnormalities. Cellular proliferation has also been seen in unmyelinated fibers (Remak fibers). In some neural tubes devoid of axis cylinders striking Schwann-cell accumulation remains, giving may in some places to fusiform enlargement of the "Schwann-cell tube". These "Schwann-cell tubes" appear as one of the late stage changes occuring in hypertrophic neuritis.