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Cranial nerve palsies

Last updated: June 2, 2021

Summarytoggle arrow icon

Cranial nerve palsy is characterized by a decreased or complete loss of function of one or more cranial nerves. Cranial nerve palsies can be congenital or acquired. Multiple cranial neuropathies are commonly seen in lesions caused by tumors, trauma, ischemia, and infections. While a diagnosis can usually be made based on clinical features, further investigation is often warranted to determine the specific etiology, which should determine the course of treatment.

For more information on facial nerve damage, see “Facial nerve palsy.”

Overview of cranial nerves and their function [1]
Cranial nerve Nerve type Function
I Olfactory nerve
  • Sensory
II Optic nerve
  • Sensory
III Oculomotor nerve
  • Motor (somatic)
IV Trochlear nerve
  • Motor
V Trigeminal nerve
  • Sensory
  • Motor (only mandibular nerve)
VI Abducens nerve
  • Motor
VII Facial nerve
  • Sensory
  • Motor (somatic)
VIII Vestibulocochlear nerve
  • Sensory
  • Balance and equilibrium: vestibular nerve
  • Hearing: cochlear nerve
IX Glossopharyngeal nerve
  • Sensory
  • Motor (somatic)
X Vagus nerve
  • Sensory (somatic)
  • Motor (somatic)
XI Accessory spinal nerve
  • Motor
XII Hypoglossal nerve
  • Motor

A useful mnemonic to remember the function of all the 12 cranial nerves is “Some Say Marry Money, But My Brother Says Big Brain Matters More”: CN I is sensory, CN II is sensory, CN III is motor, CN IV is motor, CN V is both (mixed), CN VI is motor, CN VII is both (mixed), CN VIII is sensory, CN IX is both (mixed), CN X is both (mixed), CN XI is motor, and CN XII is motor.

Remember that CN VII (Seven) controls Salivation by innervating Submandibular and Sublingual glands.

Origin and pathways of the cranial nerves

Cranial nerve

Nerve origin Foramina/Structures Nuclei Destination Pathway
CN I
  • -
CN II
CN III
  • Ocular and orbital muscles
CN IV
CN V
CN VI
CN VII
CN VIII
CN IX
  • Medulla
CN X
CN XI
CN XII

To remember the location of the cranial nerves, organize them into three groups of four: I–IV in the midbrain, V–VIII in the pons, IX–XII in the medulla.

The nuclei located in the medial brainstem are factors of 12, except 1 and 2 (i.e., CN III, CN IV, CN VI, and CN XII).

“Standing Room Only”: CN V1 exits through Superior orbital fissure, CN V2 exits through foramen Rotundum, and CN V3 exits through foramen Ovale.

The sulcus limitans in the 4th ventricle separates the CN Motor nuclei in the Medial part of the brain stem (basal plate) from the sensory nuclei in the Lateral part (aLar plate).

Etiology of CN III palsy
Structure Etiology Clinical features
Oculomotor nuclei
Basilar segment
Intracavernous segment
Intraorbital segment
Isolated oculomotor nerve palsy

For more details about oculomotor nerve lesions and drugs affecting pupillary size, see “Physiology and abnormalities of the pupil.”

Oculomotor nerve palsy leaves you down and out.

Motor fibers are in the Middle of CN III, while Parasympathetic fibers are on the Periphery of the nerve.

Compression of the oculomotor nerve can cause isolated pupillary dilation due to injury of the parasympathetic fibers. Microangiopathy (e.g., due to diabetes mellitus) typically affects the deeper somatic fibers first, causing ophthalmoplegia without pupillary dilation.

With damage to the CN IV, you cannot look at the floor.

Lesions that affect the glossopharyngeal nerve typically also affect the vagus nerve because the glossopharyngeal nerve exits the medulla above the vagus nerve.

Overview of multiple cranial neuropathies [25][26][27]
Condition Affected cranial nerve Etiology Clinical features
Chronic meningitis
  • Any
  • Insidious or subacute headache, fever, and neck stiffness
  • Additional symptoms depend on which CN is involved
Jugular foramen syndrome
Cavernous sinus syndrome
Cerebellopontine angle syndrome
Guillain-Barré syndrome
Multiple sclerosis
  1. Trochlear Nerve Palsy (Fourth Nerve Palsy). https://emedicine.medscape.com/article/1200187. Updated: November 21, 2018. Accessed: April 2, 2019.
  2. The abducens nerve (CN VI). https://teachmeanatomy.info/head/cranial-nerves/abducens-nerve/. Updated: March 13, 2019. Accessed: April 2, 2019.
  3. Duane syndrome. https://rarediseases.org/rare-diseases/duane-syndrome/. . Accessed: April 6, 2017.
  4. The vagus nerve (CN X). https://teachmeanatomy.info/head/cranial-nerves/vagus-nerve-cn-x/. Updated: January 28, 2019. Accessed: April 4, 2019.
  5. Bedside Water-Swallow Testing for Dysphagia. https://www.jwatch.org/na41936/2016/07/28/bedside-water-swallow-testing-dysphagia. Updated: July 28, 2016. Accessed: April 9, 2019.
  6. Gastroparesis Diagnosis. https://www.ucsfhealth.org/conditions/gastroparesis/diagnosis.html. . Accessed: April 9, 2019.
  7. The accessory nerve (CN XI). https://teachmeanatomy.info/head/cranial-nerves/accessory/. Updated: January 2, 2018. Accessed: April 4, 2019.
  8. The hypoglossal nerve (CN XII). https://teachmeanatomy.info/head/cranial-nerves/hypoglossal/. Updated: January 20, 2019. Accessed: April 4, 2019.
  9. Blumenfeld H. Neuroanatomy Through Clinical Cases. Wiley-Blackwell ; 2010
  10. Carroll CG, Campbell WW. Multiple Cranial Neuropathies. Seminars in Neurology. 2009; 29 (1): p.53-65.
  11. Willison HJ, Jacobs BC, van Doorn PA. Guillain-Barré syndrome. Lancet. 2016; 388 : p.717-727. doi: 10.1016/ S0140-6736(16)00339-1 . | Open in Read by QxMD
  12. Multiple Sclerosis (MS). https://www.merckmanuals.com/professional/neurologic-disorders/demyelinating-disorders/multiple-sclerosis-ms. Updated: August 1, 2016. Accessed: April 6, 2017.
  13. Peripheral Vestibular Nystagmus. https://www.aao.org/bcscsnippetdetail.aspx?id=d20f8ad8-845e-46fc-b7ed-7d00216c2726. . Accessed: April 6, 2017.
  14. DIAGNOSIS: How are vestibular disorders diagnosed?. https://vestibular.org/understanding-vestibular-disorder/diagnosis. . Accessed: April 4, 2019.
  15. The olfactory nerve (CN I) and olfactory pathway. https://teachmeanatomy.info/head/cranial-nerves/olfactory-cni/. Updated: December 24, 2018. Accessed: April 2, 2019.
  16. The optic nerve (CN II) and visual pathway. https://teachmeanatomy.info/head/cranial-nerves/optic-cnii/. Updated: October 19, 2018. Accessed: April 2, 2019.
  17. The oculomotor nerve (CN III). https://teachmeanatomy.info/head/cranial-nerves/oculomotor/. Updated: March 13, 2019. Accessed: April 2, 2019.
  18. The trochlear nerve (CN IV). https://teachmeanatomy.info/head/cranial-nerves/trochlear-nerve/. Updated: March 13, 2019. Accessed: April 2, 2019.
  19. The opthalmic division of the trigeminal nerve (CNV1). https://teachmeanatomy.info/head/nerves/ophthalmic-nerve/. Updated: December 22, 2017. Accessed: April 3, 2019.
  20. The opthalmic division of the trigeminal nerve (CNV2). https://teachmeanatomy.info/head/nerves/maxillary-nerve/. Updated: December 24, 2018. Accessed: April 3, 2019.
  21. The opthalmic division of the trigeminal nerve (CNV3). https://teachmeanatomy.info/head/nerves/mandibular-nerve/. Updated: April 2, 2018. Accessed: April 3, 2019.
  22. The facial nerve (CN VII). https://teachmeanatomy.info/head/cranial-nerves/facial-nerve/. Updated: December 31, 2017. Accessed: April 4, 2019.
  23. The vestibulocochlear nerve (CN VIII). https://teachmeanatomy.info/head/cranial-nerves/vestibulocochlear/. Updated: August 7, 2018. Accessed: April 4, 2019.
  24. The glossopharyngeal nerve (CN IX). https://teachmeanatomy.info/head/cranial-nerves/glossopharyngeal-nerve/. Updated: January 2, 2018. Accessed: April 4, 2019.
  25. Bähr M, Frotscher M. Duus' Topical Diagnosis in Neurology. Thieme Medical Pub ; 2012
  26. Ahmed HU. A case of mistaken muscles. BMJ. 2002; 324 (7343): p.962-962. doi: 10.1136/bmj.324.7343.962 . | Open in Read by QxMD
  27. Wrobel BB, Leopold DA. Smell and taste disorders.. Facial Plast Surg Clin North Am. 2004; 12 (4): p.459-68, vii. doi: 10.1016/j.fsc.2004.04.006 . | Open in Read by QxMD