Question
A 60-year-old man is brought to the emergency department because of a 1-hour history of disorientation and slurred speech. He has a 10-year history of hypertension and hypercholesterolemia. His blood pressure is 210/110 mm Hg, and pulse is 90/min. Once the patient is stabilized, an MRI of the brain is performed, which shows an infarct of the left precentral gyrus involving the region that supplies the facial nerve. Given the MRI findings, which of the following neurological findings would most be expected ?
| A. |
Decreased lacrimation of the left eye
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| B. |
Hyperacusis of the left ear
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| C. |
Flattening of the right nasolabial fold
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| D. |
Loss of taste in the posterior third of the right half of the tongue
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Show Answer
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Correct Answer � C
Explanation
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Answer C) Flattening of the right nasolabial fold
A lesion of the corticobulbar tract between the precentral gyrus and the brainstem nuclei of the facial nerve causes central facial nerve palsy.
Flattening of the right nasolabial fold
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Flattening of the right nasolabial fold would be expected in central facial nerve palsy.
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The facial motor nucleus has two regions: one that supplies the muscles of the forehead and a second that supplies the rest of the face.
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The branches of the facial nerve that innervate the forehead are activated by both cerebral hemispheres, whereas the branches innervating the lower portion of the face are only activated by the contralateral cerebral hemisphere.
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As a result, the forehead is spared with unilateral infarction of the precentral gyrus, while the contralateral lower face becomes paralyzed.
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