CBNS 116 Cranial Nerves

Olfactory

• Signal goes to through the cribriform plate → piriform cortex → other places in the brain not the thalamus

Optic

• signal goes from eyes → LGN, SC, SCn → V1 → V2 → V3, V4, V5

Oculomotor

• Superior rectus, Inferior rectus, Medial rectus, Inferior oblique

Trochlear

• Superior oblique

Trigeminal

• Ophthalmic (V1): Sensory information from forehead and around eyes

• Maxillary (V2): Sensory information from upper jaw

• Mandibular (V3): Sensory information and muscle movement of lower jaw

• Muscles for mastication (for chewing)

• Muscle for tensor tympani (dampens sound from chewing/talking)

Abducens

• Lateral rectus

Facial

• Facial expressions

• Stapedius muscle (pulls tightly to reduce movement of stapes bone in ear)

Vestibulocochlear

• Auditory pathway

• Posture, Balance, and Equilibrium

Glossopharyngeal

• Swallowing

Vagus

• Swallowing and Speaking

Spinal Accessories

• Sternomastoid and upper trap

Hypoglossal

• Muscles under the tongue

Cranial Nerve Modalities

• Somatic Motor, Branchial Motor, Parasympathetic Motor, Visceral Sensory, General Somatic Sensory, Special Somatic Sensory

Where are the motor nuclei located?

• Closer to the midline

Where are the sensory nuclei located?

• More lateral to the midline

What does SO₄ from SO₄LR₆ mean?

• Superior Oblique, Cranial Nerve 4

What does LR₆ from SO₄LR₆ mean?

• Lateral Rectus, Cranial Nerve 6

Damage to left abducens nerve

• Left eye cannot abduct when looking left

Damage to left abducens nucleus

• Left eye cannot abduct

• Right eye cannot adduct

Damage to the left MLF

• Left eye cannot adduct

One-and-a-half syndrome

• Left eye cannot adduct or abduct

• Right eye cannot adduct

Main Sensory Nucleus for Trigeminal Pathway

• Main sensory nucleus controls normal touch and proprioception

• Goes up medial lemniscus

Spinal Trigeminal Nucleus for Trigeminal Pathway

• Spinal trigeminal nucleus controls pain and temperature

• Goes down to spinal nucleus in medulla and crosses over into contralateral spinothalamic tract

What modality do CN VII, IX, and X not share?

• Somatic Motor

Nucleus Ambiguous

• Innervates muscles for speaking and swallowing

Solitary Tract

• Visceral input from the CN VII, IX, X send afferent signal

Solitary Nucleus

• Synapse visceral input in the medulla and sends afferent signal to different parts of the brain

Jaw Jerk Reflex

• CN V₃ - mandibular division

Gag Reflex

• CN IX and X - visceral sensory and special motor (nucleus ambiguous - swallowing)

Corneal Blink Reflex

• Facial somatosensory input → down to CN V nucleus → goes up CN V tract to contralateral and ipsilateral CN VII nucleus → out to the eye for rapid blinking

What LACK OF BLOODFLOW does the Medial Medullary Syndrome affect?

• Lack of blood flow to the Anterior Spinal Artery

What STRUCTURES does the Medial Medullary Syndrome affect?

• Hypoglossal Nucleus, Medial Lemniscus, and Corticospinal Tract

What are the SYMPTOMS of Medial Medullary Syndrome?

• Tongue is paralyzed to ipsilateral side of lesion

  • Tongue flops out to side of lesion

• Contralateral deficits of muscles below the medulla

  • The side that isn’t affected will slouch while the side that was affected will be normal

What LACK OF BLOODFLOW does the Lateral Medullary (Wallenberg’s) Syndrome affect?

• Lack of blood flow to the PICA

What STRUCTURES does the Lateral Medullary (Wallenberg’s) Syndrome affect?

• Vestibular Nuclei, Inferior Cerebellar Peduncle, Spinal Trigeminal Nucleus and Tract, Spinothalamic Tract, Nucleus Ambiguous

What are the SYMPTOMS of Lateral Medullary (Wallenberg’s) Syndrome?

• Trouble with balance, coordination, nocieception in face, and difficulty breathing

What LACK OF BLOODFLOW does the Weber’s Syndrome?

• Lack of blood flow to the Posterior Cerebral Artery

What STRUCTURES does the Weber’s Syndrome?

• Cerebral Peduncles and CN III

What are the SYMPTOMS of Weber’s Syndrome?

• Same symptoms as the CN III eye nerve damage: ipsilateral ptosis, pupillary dilation, lateral strabismus, difficulty with vertical eye movements

What is the special sense of Olfaction?

• Able to differentiate different smells

What is special about the Olfaction Pathway?

• Sensory information can reach the olfactory cortex without needing to go through the thalamus

• It goes through the piriform cortex first then it branches off to other places

What pathway determines what the object is?

• V₁ → V₂ → V₄

What is the special sense of Vision?

• Able to differentiate visual objects

What pathway determines where the object is?

• V₁ → V₂ → V₃ & V₅

What is the special sense of Taste (Gustation)?

• Able to differentiate different tastes

What is the Central Taste Pathway?

• Somatosensation from CN VII, IX, X → Gustatory Nucleus → Up through the Solitary Tract and Nucleus → Up to VPM in Thalamus → Out to G1

What is the special sense of Auditory and Vestibular Information?

• Able to differentiate different sounds and position/movement of the head

What is the Auditory Pathway?

• Input from IHC → CN VIII → Cochlear Nuclei → Up through Ipsilateral and Contralateral Lateral Lemniscuses → Inferior Colliculus → Medial Geniculate Nucleus → Auditory Cortex

What is the Vestibular Pathway?

• Input through CN VIII → Out to different places like cerebellum for posture and antigravity reflexes, CN III, IV, VI via MLF for eye coordination with head movements, Thalamus for awareness of head position and movement