Cranial Nerves: Nuclei, Innervation, and Dysfunction

• Lecture covers cranial nerves, nuclei, exit points, innervations, brainstem nuclei (efferent and afferent), and clinical dysfunction examples.
• Cranial nerve (CN) dysfunction examples include Vernet syndrome, trigeminal neuralgia, and vestibular schwannoma.

Cranial Nerve Classifications

• GSE: general somatic efferent
• SVE: special visceral efferent
• GVE: general visceral efferent
• GSA: general somatic afferent
• GVA: general visceral afferent
• SVA: special visceral afferent
• SSA: special somatic afferent

Brainstem Nuclei

• Oculomotor, Trochlear, Abducens, Hypoglossal, and Accessory nuclei are brainstem nuclei.
• Trigeminal and Facial motor nuclei are located in the brainstem
• The Nucleus ambiguus is a brainstem nuclei
• The Nucleus ambiguus is a brainstem nuclei
• Mesencephalic and Principal sensory nuclei are in the brainstem
• Brainstem contains Solitary, Vestibular, and Cochlear nuclei
• The Edinger-Westphal, Superior salivatory, Inferior salivatory and Dorsal vagal motor nuclei are within the brainstem

Efferent Nuclei Locations

• Midbrain contains the Edinger-Westphal, oculomotor and trochlear nuclei, as well as the red nucleus
• Pons contains the trigeminal motor, facial motor, abducens nuclei, and superior salivatory nucleus
• Inferior salivatory, nucleus ambiguous, hypoglossal, and dorsal vagal (and glossopharyngeal) are located in the medulla
• The accessory nerve is located in the rostral spinal cord
• Medial, lateral, and intermediate motor columns are in the rostral spinal cord

Afferent Nuclei Locations

• The mesencephalic nucleus is in the midbrain
• Pons contains the vestibular, spinal trigeminal, and principal trigeminal nuclei
• Medulla has the solitary, vestibular, cochlear, and spinal trigeminal nuclei
• Rostral spinal cord contains the solitary and spinal trigeminal nuclei

Cranial Nerves - Names and Numbers

• I: Olfactory
• II: Optic
• III: Oculomotor
• IV: Trochlear
• V: Trigeminal
• VI: Abducens
• VII: Facial
• VIII: Vestibulocochlear
• IX: Glossopharyngeal
• X: Vagus
• XI: Spinal Accessory
• XII: Hypoglossal

Cranial Nerves and Their Functions

• Cranial nerves, including the facial nerve, are involved in visceral sensation and function
• Cranial nerves can carry GSE, SVE, GVE, GSA, GVA, SVA, and SSA fibers

Cranial Nerve Skull Exit Points

• CN I: cribiform plate
• CN II: optic canal
• CN III, IV, V1, VI: superior orbital fissure
• CN V2: foramen rotundum
• CN V3: foramen ovale
• CN VII, VIII: internal auditory meatus
• CN IX, X: jugular foramen
• CN XI: foramen magnum/jugular
• CN XII: hypoglossal foramen

Vernet Syndrome

• Vernet syndrome is caused by the compression of the jugular foramen.
• Symptoms include loss of taste in the posterior 1/3 of the tongue (IX).
• Dysarthria and dysphagia can occur (X).
• Ipsilateral flaccid paralysis of neck muscles is present, causing the patient to "look toward lesion" (XI).

Cranial Nerves Innervating The Eye

• The oculomotor nerve (CN III) innervates the medial, inferior, and superior rectus muscles, inferior oblique, and superior levator palpebrae.
• Branches of the oculomotor nerve (CN III) innervate the ciliary muscles and pupillary sphincter (iris) via Edinger-Westphal nucleus.
• The trochlear nerve (CN IV) supplies the superior oblique muscle.
• The abducens nerve (CN VI) innervates the lateral rectus muscle.
• The lateral rectus and contralateral medial rectus muscles work in concert
• Deficit can lead to internuclear ophthalmoplegia

Trigeminal Nerve (CN V) Innervation

• Sensory fibers are analogous to DCML and ALS for most of the head region, with occiput of head by C2
• The trigeminal nerve branches into ophthalmic branch V1, maxillary branch V2 and mandibular branch V3.
• V2 and V3 neuralgia result in episodic pain ('tic douloureaux')
• V2 and V3 neuralgia can also cause ipsilateral loss of sensation.
• V1 damage causes loss of afferent corneal reflex.
• CN V controls muscles of chewing (masseter and temporalis) and controls tensor tympani (regulation of auditory input)
• Trigeminal nerve is for tensor tympani, and seventh is for stapedius

Facial Nerve (CN VII) Innervations

• Five branches supply muscles of facial expression
• The corneal reflex is controlled by the facial nerve
• CN VII controls the stapedius muscle (regulation of auditory input)
• The facial nerve also provides parasympathetic control of lacrimal glands, sublingual and submandibular glands.
• Taste in anterior 2/3 of tongue is another function of CN VII
• Solitary Nucleus is the only part of the cranial nerves that affects VA

Vestibulocochlear Nerve (CN VIII)

• It is responsible for vestibular function (balance via semi-circular canals)
• CN VIII facilitates auditory function (hearing via the cochlea)

Glossopharyngeal Nerve (CN IX)

• It controls taste in the posterior 1/3 of the tongue and carotid chemo- and baro-receptors.
• Responsible for the stylopharyngeus muscle
• Controls parasympathetic function of parotid gland
• Solitary nucleus plays a part in this

Vagus Nerve (CN X)

• Contains the pharyngeal muscles for swallowing and laryngeal muscles for voice.
• The major source of parasympathetic control of heart, lungs, and GI tract.

Spinal Accessory Nerve (CN XI)

• Supplies the trapezius and sternocleidomastoid muscles
• Damage leads to weakness to these muscles, manifesting as the patient looking towards the lesion

Hypoglossal Nerve (CN XII)

• The hypoglossal nerve controls intrinsic and extrinsic tongue muscles

Cranial Nerve Nuclei - Locations

• The slide set contains sections discussing caudal and rostral aspects
• Some nuclei are located within the medulla or pons
• Spinal trigeminal nucleus is located in caudal pons
• The abducens nucleus is in caudal pons
• The facial nucleus is located in the caudal pons
• Vestibular nuclei are in caudal pons
• The Spinal trigeminal is in rostral medulla
• Rest of nuclei are too location specific to note