Table 14-1.
Chronologic Sequence of Changes within Infarcted Tissue (in the Living Animal) after an Ischemic Event
| Time Following Ischemic Event | Tissue Change |
|---|---|
| Immediate (seconds) | Cessation of blood flow (ischemia) and accumulation of waste products |
| Few minutes | Cellular injury and death; necrosis and edema; hemorrhage (especially in gray matter) |
| 20 minutes | First microscopic evidence of neuronal injury (perfusion-fixation) |
| 1-2 hours | First microscopic evidence of neuronal injury (immersion-fixation) |
| 2 hours | Pale staining of infarct microscopically (white matter); swelling of capillary endothelium; increase in size of astrocytic nuclei |
| 3-5 hours | Ischemic cell change in most neurons; swelling of oligodendroglia and astroglia; beginning clasmatodendrosis of astrocytes |
| 6-24 hours | Beginning neutrophilic infiltration; alteration of myelin (pale staining), 8-24 hours; degeneration and decrease of oligodendroglia, 8-24 hours; astrocytic swelling and retraction and fragmentation of processes (clasmatodendrosis), and degeneration*; cytoplasm of astrocytes visible, 8-24 hours*; vascular degeneration and fibrin deposition, 8-24 hours; thrombosis,† 6-24 hours; beginning endothelial proliferation at margin of infarct, 9 hours |
| 8-24 (up to 48) hours | Initial gross detection of infarct unless hemorrhagic; infarct edematous (swollen), soft, pale, or hemorrhagic and demarcated |
| 1-2 days | Swelling of axons and myelin sheaths; prominent neutrophilic infiltration |
| 2 days | Prominent loss of neuroectodermal cells; continued proliferation of endothelial cells; reduced number of neutrophils; beginning increase in mononuclear cells (gitter cells) |
| 3-5 days | Prominent number of mononuclear cells (gitter cells); disappearance of neutrophils; continued endothelial cell proliferation; number of capillaries appear increased; beginning of astrocytic proliferation (often at margin of infarct) |
| 5-7 days | Grossly, swelling of infarct reaches maximum |
| 8-10 days | Reduction in gross swelling of infarct; liquefaction necrosis; prominent number of mononuclear cells (gitter cells); continued endothelial cell proliferation; beginning fibroblastic activity with collagen formation, variable but most prominent in CNS tissue adjacent to the meninges; beginning increase of astroglial fiber production, 5-13 days |
| 3 weeks-6 months | Mononuclear cells decreased; astroglial fiber density increased (especially at margin); astrocytic proliferation reduced; astrocytes return to original appearance; cystic stage of infarct, 2-4 months; vascular network may be present within cyst; endothelial cell proliferation reduced |
CNS, Central nervous system.
*
The degree of astrocytic injury depends on location (e.g., central or peripheral) of the cells within the infarct.
†
Obviously, thrombosis may occur earlier than 6 hours. This is the time when it may initially be prominent.