A 70-year-old retired insurance broker complains of difficulty in walking, having to consciously lift up his feet so he does not trip stumble or fall. Both feet are affected equally. He has no sensory complaints and no pain. This has been worsening over the past three years, and he has had to give up his beloved hiking. The symptoms are improved while wearing tall boots and worse when walking around the house with house slippers. What is the likely location of the pathology in this man?a) Peripheral nerve
b) Brainstem
c) Distal muscle
d) Lumbar spinal cord
e) Frontal motor area of the cerebral cortex

The correct answer is A.

Peripheral nerve.

Explanation:

Pure motor neuropathy would first affect the distal extremity farthest

away from the motor neuron based simply on the length of the nerve.

The symptoms are symmetrical. Support of the tall, rigid boot would

help to maintain the function of the weakened foot and ankle muscles;

house slippers would do the opposite. Frontal motor area of the cerebral cortex is incorrect because the symptoms are bilateral,symmetrical, and distal; most bilateral, symmetrical distal motor symptoms are not caused by cortical pathology, which would require symmetrical, bilateral brain lesions. Brainstem is incorrect. Because the brainstem is compact, filled with multiple ascending and descending motor and sensory tracts to cranial and spinal nerves, lesions affecting bilateral descending motor tracts would also impinge on other structures, causing a multitude of other symptoms and signs. Lumbar spinal cord is incorrect because a spinal lesion causing this pattern of bilateral distal motor dysfunction would also affect sensory and autonomic functions. Distal muscle is incorrect because primary muscle conditions such as myopathy or muscular dystrophy generally will affect the larger, proximal muscles first, based on bulk and strength alone.

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