Cranial Nerve #3: Oculomotor Nerve

Description and Pathology:

The third cranial nerve controls most of the eyes movement including constriction of the pupil and maintenance of an open eyelid. The oculomotor nerve controls the eyes movement in conjunction with cranial nerves IV and V. As a result, when a pathology occurs in eye movement, all three cranial nerves III, IV, and V and tested together.

Pathology: Oculomotor Nerve Palsy

Oculomotor Palsy, otherwise known as paralysis of the oculomotor nerve, is a real pathology; however, oculomotor nerve palsy is rare.  Oculomotor nerve palsy can occur as a result of direct trauma, multiple sclerosis, or diabetes. The image below is a frontal view of an individual with oculomotor nerve palsy. Another name given to this pathology is “down n’ out” because of the characteristic down and abducted position of the eye. As we can see the individual’s left eye is looking inferior and lateral giving the characteristic “down n’ out” look.

If we were to look at an inferior view of the brain, as in the image below, we can notice that the oculomotor nerve is damaged. This damage can occur as a result of the aforementioned, or increased intracranial pressure. Other pathologies that my occur due to a damaged oculomotor nerve are diplopia (double vision), ptosis (drooping of the eyelid), or mydriasis (dilation of the pupil).



The image below represents many pathologies (ptosis, mydriasis, and diplopia due to the abducted position of the eye) associated with damage to the oculomotor nerve.

Literature Cited:

“CN3 pathology.” Department of Radiology and Radiological Sciences. N.p., n.d. Web. 6 May 2012. <;

Goodwin, M.D, James. “Medscape: Medscape Access.” Medscape: Medscape Access. N.p., n.d. Web. 6 May 2012. <;.

“Medscape: Medscape Access.”Medscape: Medscape Access. N.p., n.d. Web. 6 May 2012. <;.



4 thoughts on “Cranial Nerve #3: Oculomotor Nerve

    • Cranial nerve # 3, the oculomotor nerve, is now up, please make sure to take a look at some of the pictures. Cranial Nerve # 4, the trochlear nerve, should be up shortly. Thank you for you for your patience.

      • Looks Fantastic! You have done a really good job with this entire wiki. The biological relevance and the concise and summarized explanations of each nerve and associated disease is top notch. At some points I wish there was more, but understandably that could over do it. Nice work.

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