Stereology and Ultrastructure of Chronic Phase Axonal and Cell Soma Pathology in Stretch-Injured Central Nerve Fibers

Abstract Magnetic resonance imaging (MRI) suggests that with survival after human traumatic brain injury (TBI), there is ongoing loss of white and grey matter from the injured brain during the chronic phase. However; direct quantitative experimental evidence in support of this observation is lacking. Using the guinea pig stretch-injury optic nerve model, quantitative evidence by stereology of damage to the optic nerve and retina was sought. Stretch injury was applied to the right optic nerve of 15 adult male guinea pigs. Three animals each at 1, 2, 3, 8, or 12 weeks' survival were killed and prepared for transmission electron microscopy (TEM). The estimated number of intact and injured axons within bins of transverse diameters 0–0.5, 0.51–1.0, 1.01–1.5, 1.51–2.0, 2.01–2.5, and 2.51–3.0 μm in the middle segment of each injured optic nerve and from 5 control animals were compared across all survival time points. The estimated numbers of intact and pyknotic retinal ganglion cells from the same animals were a...