Oculomotor Nerve Palsy
Basics
Description
Description
- There are six muscles that control eye movement innervated by three cranial nerves (CN):
- CN III, or oculomotor nerve, innervates 4 of the 6 eye muscles and also innervates the lid and pupil:
- Medial rectus:
- Adduction – moves eye medially toward nose
- Superior rectus:
- Elevation – moves eye upward
- Intorsion – rotates top of eye toward nose
- Slight adduction
- Inferior rectus:
- Depression – moves eye inferiorly
- Extorsion – rotates top of eye away from nose
- Slight adduction
- Inferior oblique:
- Extorsion – rotates top of eye away from nose
- Slight elevation and abduction
- Levator palpebrae superioris:
- Raises eyelid
- Iris sphincter pupillae and ciliary muscles
- Constricts pupil (miosis)
- Innervated by parasympathetic fibers of CN III
- Medial rectus:
- CN IV innervates the superior oblique:
- Extorsion – rotates top of eye away from nose
- Depression and slight abduction (lateral rotation)
- CN VI innervates the lateral rectus:
- Moves eye laterally (abduction)
- CN III, or oculomotor nerve, innervates 4 of the 6 eye muscles and also innervates the lid and pupil:
- Oculomotor nerve palsy results from damage to CN III or a branch thereof resulting in abnormal eye movements, lid ptosis, and/or changes to the pupil:
- Complete oculomotor nerve palsy:
- Eye “down and out,” ptosis, pupil dilated
- Most often caused by compressive lesions
- 95–97% of compressive lesions involve the pupil
- Parasympathetic fibers sit peripherally in CN III
- Mydriasis is often first symptom of compression
- Pupil-sparing complete oculomotor nerve palsy:
- Almost always ischemic from microvascular disease due to underlying diabetes, hypertension, and/or hyperlipidemia
- Ischemic injuries often spare the pupil because the outer parasympathetics are not affected
- Often benign and fully resolves in 3 mo
- Incomplete oculomotor nerve palsy (more common):
- Partial loss of function of CN III
- Most often caused by ischemia of vasa vasorum
- Complete oculomotor nerve palsy:
- Pathophysiology of oculomotor nerve palsy:
- Midbrain lesions of the oculomotor nucleus leads to bilateral CN III palsy (ischemia of the basilar artery)
- Lesions leaving CN III nucleus are often associated with other neurologic findings such as hemiplegia or ataxia (Weber syndrome, Benedikt syndrome)
- Lesions in the subarachnoid space cause complete palsy with pupil involvement (compressive aneurysms) or complete palsy with pupil sparing (ischemia due to risk factors)
- Lesions in the cavernous sinus and superior orbital fissure can cause isolated CN III palsy, but often are associated with CN IV, CN VI, and maxillary division of CN V dysfunctions
- Lesions in the orbit are associated with visual loss (CN II), ophthalmoplegia (CN III, IV, VI), and proptosis and caused by trauma, mass, inflammation:
- Incomplete CN III palsy originates here as the nerve divides into superior and inferior divisions
Etiology
Etiology
- Acquired etiologies:
- Vascular disorders:
- Diabetes mellitus (DM)
- Hypertension and heart disease
- Atherosclerosis
- Aneurysm (esp posterior communicating artery)
- Arteriovenous malformation (AVM)
- Intracranial hemorrhage (nonaneurysmal)
- Cerebral vascular accident
- Cavernous sinus thrombosis
- Infectious:
- Meningitis
- Syphilis
- Herpes zoster
- Inflammatory:
- Sarcoidosis
- Giant cell arteritis, vasculitis
- Systemic lupus erythematous
- Neoplastic:
- Intracranial tumor
- Pituitary tumor
- Orbital tumor
- Leukemia
- Degenerative:
- Myasthenia gravis
- Guillain–Barré
- Trauma – head injury, recent or remote
- Migraine headache
- Iatrogenic:
- Chemotherapy
- Radiation therapy
- Idiopathic:
- Idiopathic intracranial hypertension (IIH)
- Congenital etiologies are often unknown but some with familial tendency
- Vascular disorders:
Pediatric Considerations
- Trauma is the most common cause of acquired oculomotor nerve palsies:
- Includes birth trauma
- Can also see in neurofibromatosis, ophthalmologic migraine with recurrent CN III palsy, and spontaneous intracranial hypotension
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Citation
Schaider, Jeffrey J., et al., editors. "Oculomotor Nerve Palsy." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307151/all/Oculomotor_Nerve_Palsy.
Oculomotor Nerve Palsy. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307151/all/Oculomotor_Nerve_Palsy. Accessed September 7, 2024.
Oculomotor Nerve Palsy. (2016). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (5th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307151/all/Oculomotor_Nerve_Palsy
Oculomotor Nerve Palsy [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2024 September 07]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307151/all/Oculomotor_Nerve_Palsy.
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