Question
A 52-year-old man with a history of gastric cancer that was treated with subtotal gastrectomy dies in a motor vehicle collision. At autopsy, examination of the spinal cord shows unilateral atrophy of the neurons in the area indicated by the arrow. Neurological examination of the patient when he was still alive would most likely have shown which of the following findings?
| A. |
Decreased positional sense in the ipsilateral leg
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| B. |
Decreased sense of temperature in the ipsilateral arm
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| C. |
Decreased vibratory sense in the ipsilateral arm
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| D. |
Decreased sense of pain in the contralateral leg
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Show Answer
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Correct Answer � A
Explanation
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Answer A) Decreased positional sense in the ipsilateral leg
The region of the spinal cord indicated in the image is affected by vitamin B12 deficiency, which occurs in about 15% of patients with prior subtotal gastrectomy (due to insufficient intrinsic factor synthesis).
Decreased positional sense in the ipsilateral leg
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The area indicated by the arrow corresponds to the fasciculus gracilis of the dorsal column. This part of the spinal cord consists of afferent neurons, which transmit the sensations of proprioception, vibration, pressure, and fine touch from the ipsilateral lower trunk and extremities.
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Atrophy of this area due to neuronal demyelination can be caused by vitamin B12 deficiency and results in decreased function of these neurons, leading to decreased positional sense (i.e., proprioception) and vibratory sensation in the ipsilateral leg.
Vitamin B12 deficiency can also lead to combined degeneration of the dorsal and lateral columns of the spinal cord (i.e., subacute combined degeneration of spinal cord), which classically manifests with decreased proprioception and vibratory sensation, spasticity, and ataxia
