October 13, 2010

USMLE 1 Question 8

A 70 year old known hypertensive man presents to the general practitioner complaining of sudden onset of a drooping right eyelid and slurred speech. Examination revealed the tongue deviated to the right. A Horner's syndrome on the right was diagnosed.

Further examination showed a loss of pain sensation of the left side. The physician also noted a poor visual acuity from both eyes.

Which area of the brain is involved in ischaemia?

a) spinal cord at the level of C2
b) dorsolateral medulla
c) anterior pons
d) right side of midbrain
e) left side of midbrain








ANSWER
The correct answer is A


Explanation
This patient's clinical condition suggests ischemia of the dorsolateral medulla.

Involvement of the ninth and tenth cranial nerve nuclei result in ipsilateral tongue deviation to the right and ipsilateral palatal weakness, respectively.

Involvement of the central sympathetic pathway results in an ipsilateral Horner's syndrome.

Damage to the lateral spinothalamic tract results in contralateral loss of pain and temperature sensation.

The poor visual acuity in this case was irrelevant and an incidental finding- this was corrected with reading glasses

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