Subtitle: Central chromatolysis (axonal reaction): what happens to the neuron after axonal injury, where it is best seen, how it differs from red neurons and Wallerian degeneration, and 8 MCQs.
Author: PathologyMCQ Editorial Board
Category: Neuropathology
Last Updated: October 2026
Read Time: 4 minutes
At-a-Glance
- Central chromatolysis is the cell-body change of the axonal reaction, seen after an axon is cut or badly damaged.
- Best seen in anterior horn cells of the spinal cord.
- Features: swollen, rounded cell body; Nissl substance dispersed to the periphery; nucleus pushed to the edge; enlarged nucleolus.
- It reflects increased protein synthesis for regeneration and is potentially reversible.
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What Happens in the Axonal Reaction
- Axonal injury triggers the cell body to make proteins for axonal regrowth.
- The cell body enlarges and rounds up.
- The nucleus moves to the periphery and the nucleolus enlarges.
- Nissl substance (rough ER and ribosomes) disperses from the centre to the periphery, leaving a pale centre: central chromatolysis.
- Changes start within days, peak at about 1–2 weeks and can recover if regeneration succeeds.
Comparison With Other Neuronal Changes
Neuronal reactions to injury
| Change | Morphology | Cause | Reversible? |
|---|---|---|---|
| Central chromatolysis (axonal reaction) | Swollen round cell, peripheral nucleus, central loss of Nissl | Axonal transection or injury | Yes |
| Red (eosinophilic) neuron | Shrunken, angular, hypereosinophilic cytoplasm, pyknotic nucleus | Acute hypoxia-ischaemia (12–24 h) | No |
| Wallerian degeneration | Distal axon and myelin breakdown, myelin ovoids, macrophages | Axonal transection | Distal segment lost |
| Neuronophagia | Microglia clustering around a dying neuron | Viral infection, e.g. polio | No |
| Simple atrophy | Shrunken neuron, lipofuscin, gliosis | Neurodegeneration | No |
Other Causes of Chromatolysis-Like Change
- Pellagra: chromatolysis-like change in Betz cells and brainstem neurons.
- Ballooned neurons in corticobasal degeneration and Pick disease (achromatic, alphaB-crystallin positive).
- Motor neuron disease and some storage disorders can show swollen neurons.
Related reads: inclusions in neurodegenerative diseases → · Lewy body vs Pick body →
Test Yourself: 8 MCQs
Neuronal reactions to injury: 8 MCQs
Axonal reaction, red neurons and Wallerian degeneration, with instant explanations.
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Exam Pearls
- Central chromatolysis = axonal reaction, best in anterior horn cells.
- Swollen cell, peripheral nucleus, big nucleolus, Nissl pushed to the edge.
- Red neurons = irreversible ischaemic injury at 12–24 hours.
- Wallerian degeneration is the distal axon; chromatolysis is the cell body.
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References
- Kumar V, Abbas AK, Aster JC. Robbins and Cotran Pathologic Basis of Disease. 10th ed. Elsevier; 2020. Chapter 28.
- Love S, Perry A, Ironside J, Budka H, eds. Greenfield’s Neuropathology. 9th ed. CRC Press; 2015.
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