Question
An investigator is studying cellular repair mechanisms in various tissues. One of the samples being reviewed is from the anterior horn of the spinal cord of a patient who was involved in a snowboard accident. Pathologic examination of the biopsy specimen shows dispersion of the Nissl bodies, swelling of the neuronal body, and a displacement of the nucleus to the periphery in numerous cells. Which of the following is the most likely explanation for the observed findings?
| A. |
Neurodegenerative changes
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| B. |
Central chromatolysis
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| C. |
Early ischemic damage
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| D. |
Wallerian degeneration
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Show Answer
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Correct Answer � B
Explanation
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Answer B) Central chromatolysis
This reaction is most commonly seen in neurons following injury to their axons.
Central chromatolysis
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Central chromatolysis is a reaction of a neuronal cell body (also known as the soma) in response to an axonal injury.
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It is characterized by swelling of the neuronal body, dispersion of the Nissl bodies, and displacement of the nucleus to the periphery.
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These changes reflect an increase in protein synthesis aimed at restoring the integrity of the damaged axon. Chromatolysis occurs concurrently with Wallerian degeneration.
Neurodegenerative changes
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Neurodegenerative changes occur in response to the loss of function and structure of neurons in neurodegenerative diseases (e.g., Parkinson disease, Alzheimer disease, Huntington disease).
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These changes manifest in many different ways depending on the neurodegenerative diseases.
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Mechanisms include genetic mutations, protein misfolding, intracellular defects (e.g., of protein degradation pathways, mitochondria, membrane, DNA, or axons), defective programmed cell death, and transglutaminases. However, the described findings in this question suggest another etiology.
Early ischemic damage
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Early ischemic damages manifest with retraction of the cellular outlines, pyknosis, disappearance of the Nissl bodies, and eosinophilic condensation of the cytoplasm, unlike the biopsy findings here.
Wallerian degeneration
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Wallerian degeneration is a process that occurs in response to a proximal axonal or neuronal cell body injury.
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It is characterized by degeneration of the distal segment of the transected nerve fiber and axonal retraction proximally but does not cause the changes described in the biopsy findings here.
