All are seen in 3rd nerve palsy except:
Correct Answer: Miosis
Description: C i.e. Miosis 3rd (occulomotor) nerve innervates 4 extraocular muscles (i.e. RIMS = rectus of inferior, medial & superior; and inferior oblique) in addition to levator pulpebrae and pupillary sphincter. - So when the palsy is complete, there is complete ptosis with a dilated pupil that responds neither to light nor near. The eye is deted out (laterally) and usually, but not always, down. Functions of the other nerves is normal and can be assessed by evaluation of abduction (6th CN) and by observing incyclotorsion on attempted depression (4th CN). If the pupillary light reaction is spared, the 3rd CN palsy probably does not result from compression or injury, but more likely from small vessel disease such as might be seen in diabetics. This is an old clinical rule of thumb, but a very small number of pupil sparing third cranial nerve palsies arise from midbrain infarct.
Category:
Ophthalmology
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