Inner Ear Inner Ear

Cranial Nerve Anatomy and Nuclei

This section will not cover each nerve equally; remaining true to the theme of this website, most of the following information will relate the cranial nerves to balance and dizziness (when possible). Because the focus of this site is general neurological concepts, the specific courses travelled by these nerves are also absent from this discussion. Excellent resources for a comprehensive treatment of the twelve cranial nerves are abundant, so are not recreated here.

The Cranial Nerves

Cranial Nerves
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CN I - Olfactory

The author is unaware of any relation of CN I to issues of balance and dizziness.

CN II - Optic

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CN III - Oculomotor

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CN IV - Trochlear

The fourth cranial nerve nucleus is located at the ventral border of the periaqueductal gray matter, at the level of the inferior colliculus. It innervates the contralateral superior oblique muscle. The trochlear nerve itself is the thinnest and longest-coursing of the twelve cranial nerves, predisposing it to trauma.

CN V - Trigeminal

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CN VI - Abducens

The sixth cranial nerve nucleus is located in the caudal pons, situated on the floor of the fourth ventricle. Motor neurons in the abducens nucleus innervate the ipsilateral lateral rectus (LR). Internuclear neurons indirectly innervate the contralateral medial rectus (MR); that is, CN VI internuclear neurons innervate contralateral MR motoneurons (which then innervate the MR). The internuclear neurons use the medial longitudinal fasciculus (MLF) to reach the contralateral motoneurons. The abducens nucleus, then, is involved with the extraocular muscles responsible for yoked horizontal eye movements. For a schematic representation of these pathways, refer to the section discussing the neurology of horizontal eye movements.

CN VII - Facial

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CN VIII - Vestibulocochlear

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CN IX - Glossopharyngeal

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CN X - Vagus

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CN XI - Spinal Accessory

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CN XII - Hypoglossal

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