What are physical exam findings in unilateral third cranial nerve palsy (oculomotor cranial nerve palsy)?

Updated: Oct 08, 2018
  • Author: James Goodwin, MD; Chief Editor: Andrew G Lee, MD  more...
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Answer

Horizontal deviation is divergent or temporal (exotropia) because of weakness of the medial rectus muscle of the involved side. Vertical deviation results from weakness of the superior rectus, inferior oblique (both elevators), and inferior rectus (depressor) muscles.

Residual function of both the superior oblique muscle (depressor, intact fourth cranial nerve function) and the lateral rectus muscle (abductor, intact sixth cranial nerve function) tends to produce downward and outward deviation of the involved eye. A way to remember this combination is to think of a losing boxer, "down and out."

In very mild cases, one might have to resort to eliciting latent deviation or phoria with Maddox rod or alternate cover testing (to dissociate the 2 eyes and interrupt fusion).

Ptosis results from weakness of the levator palpebrae, and this often is complete or nearly so, in which case the pupil is covered and the patient cannot see from the involved eye.


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