What is abducens nerve palsy (sixth cranial nerve palsy)?

Updated: Nov 19, 2018
  • Author: Michael P Ehrenhaus, MD; Chief Editor: Edsel Ing, MD, MPH, FRCSC  more...
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Answer

Cranial nerve VI, also known as the abducens nerve, innervates the ipsilateral lateral rectus (LR), which functions to abduct the ipsilateral eye. The sixth cranial nerve has a long subarachnoid course. The sixth nerve nucleus is located in the pons, just ventral to the floor of the fourth ventricle and just lateral to the medial longitudinal fasciculus (MLF). About 40% of its neurons project into the ipsilateral MLF only to cross over to the contralateral side and ascend to innervate that contralateral medial rectus subnucleus to participate in contralateral eye adduction. [1, 2, 3]

The abducens nerve emerges from the brainstem at the pontomedullary junction to enter the subarachnoid space, coursing upward between the pons and clivus to enter the Dorello canal. At the petrous apex, it angulates to enter the cavernous sinus and travels in close proximity to the internal carotid artery. The abduces nerve then proceeds through the superior orbital fissure and innervates the lateral rectus muscle.


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