What are the physical findings in nuclear 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

Nuclear third cranial nerve palsy demonstrates, in addition to the ipsilateral findings, contralateral ptosis or no ptosis (single central caudate subnucleus innervates both lids) and elevation palsy (superior rectus subnucleus is crossed).

The contralateral ptosis stems from the bilateral distribution of innervation to the levator from the caudal central subnucleus.

Ptosis is typically more complete ipsilateral to the lesion because function is lost in both the ipsilateral neural cell bodies and their fibers on the lesioned side, plus the crossed fibers coursing through the lesion from the other side.

There is partial ptosis contralateral to the lesion because of the residual integrity of the uncrossed neural cell bodies and fibers from the caudal central subnucleus contralateral to the lesion.

Superior rectus nucleus output is totally contralateral with fascicles from the nucleus on one side coursing through the opposite superior rectus subnucleus. A lesion of the superior rectus subnucleus on one side causes bilateral elevation palsy. The deficit ipsilateral to the lesioned nucleus reflects involvement of fascicles coming from cell bodies on the opposite side, and the deficit contralateral to the lesion reflects loss of the cell bodies in the lesioned nucleus.


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