Histopathological Changes of the Corticospinal Tract Following Hemorrhagic and Ischemic Stroke

Previous data on the time course of corticospinal tract (CST) degeneration after stroke are scarce, especially in the early phase. Using post-mortem histomorphological and immunohistochemical methods, CST degeneration (its temporal dynamics and its association with stroke type) was investigated in the medulla oblongata pyramids in twenty-two cases: nine patients with ischemic stroke and eleven with hemorrhagic stroke and two patients with very long survival after multiple strokes. CD68 and neurofilament immunohistochemistry and Klüver-Barrera staining were applied to assess microglial activation and axonal and myelin degeneration, respectively, and statistical methods were used to investigate the relationship between microglial density, stroke type, and survival time. Strong microglial activation starts on day 3 after stroke and increases over time, with the first signs of axon degeneration and myelin degradation observed from day 7 after stroke. Histological changes and their temporal dynamics do not differ between hemorrhagic and ischemic stroke. Our results show that myelin degeneration starts earlier than previously suggested and is observed almost simultaneously with axon degeneration, whereas microglial activation increases steadily from day 3 onwards in both ischemic and hemorrhagic stroke.