Oculomotor nerve palsy
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Oculomotor nerve palsies, or third nerve palsies, result in weakness of the muscles supplied by the oculomotor nerve, namely the superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris muscles.
If the pupil is normal-sized and reactive to light, it is called a pupil-sparing third nerve palsy; conversely if the pupil is enlarged and non-reactive, it is called a non-pupil sparing third nerve palsy.
Classically, patients present with diplopia and physical exam findings ipsilateral to the oculomotor nerve (CN III) lesion:
"down and out" ocular positioning
abduction, slight depression, and intorsion (due to paralysis of adduction, elevation, and depression)
due to neuropathy affecting levator palpebrae superioris
+/- enlarged unreactive pupil
if present, suggests compression of CN III, because the parasympathetic pupillary fibers are located peripherally in the nerve and are more likely affected by external compression
It has numerous possible etiologies which can be divided according to which portion of the nerve is affected:
dorsal midbrain (nuclear lesions): usually due to small regions of infarction; often no other neurological symptoms
rapidly enlarging with or without SAH is the most common cause, and usually involves only the oculomotor nerve
ischemic involvement of the nerve will usually be pupil sparing whereas aneurysmal compression usually involves the pupil
basal meningeal processes including infection, neoplastic infiltration, and inflammatory lesions (e.g. sarcoidosis) often involve additional cranial nerves
cavernous sinus portion
neoplasms, most commonly pituitary macroadenomas extending into the sinus, meningiomas of the sella or sinus and any other sinus mass (e.g. trigeminal schwannomas) can compress the nerve against the interclinoid ligaments
Treatment and prognosis
In post-traumatic oculomotor nerve palsy, gaze movement training and steroid injections may be helpful 2.
- 1. Lo C, Huang C, Hsu C et al. Neuroimaging of Isolated and Non-Isolated Third Nerve Palsies. Br J Radiol. 2012;85(1012):460-7. doi:10.1259/bjr/38090653 - Pubmed
- 2. Kim T, Nam K, Kwon B. Isolated Oculomotor Nerve Palsy in Mild Traumatic Brain Injury. Am J Phys Med Rehabil. 2020;99(5):430-5. doi:10.1097/PHM.0000000000001316 - Pubmed