1

MA 636

Cranial Nerves I - VI

Reading: Moore and Agur, p.643-660

M.Pizzimenti, Ph.D.

LEARNING OBJECTIVES

• Create a list matching the cranial nerve name with its associated number

• Classify cranial nerves as belonging to special sensory, motor, sensory and parasympathetic

function.

• Describe the significant functions (sensory and/or motor) performed by each CN.

• Trace the course of each CN from the brain to its target(s).

• How will you test the integrity of individual nerves?

OVERVIEW

• Twelve pairs of cranial nerves arise

from brain

• pass through certain foramina of skull

to be distributed primarily in the head

and neck

- Vagus n. continues into the

thorax and abdomen

• Referred to either by their given name

(e.g., vagus n.) or by the assigned

Roman Numeral (e.g., CN X)

Functions

• Sensory

- Special: olfaction (smell),

vision, hearing, balance, taste

- General: pain, temperature, hot, cold

- Visceral: sensations from organs, sinuses, bronchi, etc.

• Motor

- Somatic: voluntary striated m.

- Branchial: innervation of m. derived from the (embryonic) pharyngeal arches

- Parasympathetic: innervating glands and smooth m.

Functional Components of Cranial Nerves

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

I Olfactory *

II Optic *

III Oculomotor * *

IV Trochlear *

V Trigeminal * *

VI Abducent *

VII Facial * * * * *

VIII Vestibulocochlear *

IX Glossopharyngeal * * * *

X Vagus * * * * *

XI Spinal Accessory *? *?

XII Hypoglossal *

2

MA 641

MA 652

OLFACTORY NERVE (CN I)

• Special sense of smell (olfaction)

• Olfactory receptor neurons in mucosa of roof of nasal cavity

• Synapse in olfactory bulb

• Bulb is connected to the olfactory tract, technically a part of the brain

• Receptor neurons pass through foramina in the

cribriform plate of ethmoid bone

• Subject to “shear” injury during head trauma or

ethmoid fracture

Clinical Test

• Check for anosmia (loss of smell)

• Patient is asked to differentiate distinct odors (e.g.,

coffee, vanilla) with eyes closed. Test each side

independently.

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

I Olfactory *

OPTIC NERVE (CN II)

• Special sense: vision

• Ganglionic cells in retina convey

information from eye to brain

• optic ‘nerve’ from eye to brain via optic

nerve and tracts

• ‘Nerve’ passes through optic canal (with ophthalmic a.) into

orbit

• Visual fields

- Temporal

- Nasal

- Superior

- Inferior

3

MA 643

MA 534

• Chiasm

• Visual Field Defects

(Injuries)

- Right-side blindness

- Bitemporal

hemianopsia

- Left homonymous hemianopsia

• Clinical Test- Reading eye Chart/color/field of view. Visual fields are determined by

examining when patient observes an object moving from lateral to medial, superior to inferior.

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

II Optic *

OCULOMOTOR NERVE (CN III)

• Emerges through cavernous sinus

• Leaves cranial cavity via the superior orbital fissure to gain access to the orbit

• Motor and parasympathetic components

Motor

• Within fissure n. divides into superior and inferior divisions

• Major motor n. for 4 of 6 extraocular mm. and the m. of the upper eyelid

- Superior rectus m.

- Inferior rectus m.

- Medial rectus m.

- Inferior oblique m.

- levator palpebrae superioris

m.

4

MA 654

Parasympathetics

• Preganglionic cell bodies located in the Edinger-Westphal nucleus (within midbrain)

• Preganglionic fibers

travel as part of CN III

(inf. division) to reach

the ciliary ganglion

• Postganglionic cell

bodies located in ciliary

ganglion

• Postganglionic fibers

travel along branches of

CN V (short ciliary nn.)

to enter globe

• Function:

- sphincter pupillae

(causes constriction

of pupil)

- ciliary mm. of lens,

causes

accommodation

(thickening) of lens

for near vision

• Injury

- Eye turns out

(lateral strabismus) because lateral rectus pulls it laterally; i.e., it is unopposed by medial

rectus

- Ptosis- upper eyelid droops; due to dysfunction of levator palpebrae superioris.

- Dysfunction of pupil reflex (i.e., pupil does not constrict)

Clinical Test

• Patient is asked to follow with his or her eyes the examiner’s finger as it moves in an “H

pattern.”

• Pupillary reflex

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

III Oculomotor * *

• [LR6SO4]3

• Eye Simulator

! http://cim.ucdavis.edu/EyeRelease/Interface/TopFrame.htm

Edinger-

Westphal

nucleus (midbrain)

Ciliary ganglion

Ciliary mm.

& sphincter pupillae

5

MD 1142

TROCHLEAR NERVE (CN IV)

• Motor to 1 extraocular m.

- Superior oblique m.

• Emerges from dorsal surface of midbrain

• Passes through cavernous sinus

• Leaves cranial cavity via the superior orbital

fissure to gain access to orbit

• Found on superior surface of sup. oblique m.

• Injury

- Extortion (superior pole of globe moves laterally) of the affected eye

- Double vision (diplopia) and weakness of downward gaze

- Difficulty with vision when going down stairs

Clinical Test

• Patient is asked to follow with his or her eyes the examiner’s finger as it moves in an “H” or

“box” pattern.” Look for difficulty with downward gaze, when patient ‘looks medially.’

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

IV Trochlear *

ABDUCENS NERVE (CN VI)

• Motor to 1 extraocular m.

- Lateral Rectus m.

• Emerges from the pons/medually junction

• Passes through cavernous sinus

• Leaves cranial cavity via the superior orbital fissure

to gain access to orbit

• Found on medial surface of lateal rectus m.

• Injury

- Medial strabismus

- Double vision (diplopia)

Clinical Test

• Patient is asked to follow with his or her eyes the examiner’s finger

as it moves in an “H” or “box” pattern.” Damaged causes medial

deviation (adduction) of the globe

• Individual extraocular mm. do not work independently. They are coordinated so that we have

smooth pursuit, saccadic movements, and conjugate gaze.

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

VI Abducent *

6

GA 807

V1

V2

V3

TRIGEMINAL NERVE (CN V)

Overview

• ‘three twins’ has three major divisions

- ophthalmic (V1): sensory

- maxillary (V2): sensory

- mandibular (V3): motor and sensory

• exits pons

• Trigeminal sensory ganglion sits lateral to sella

turcica within cavernous sinus

• acts as a ‘highway’ for parasympathetic components of CN III, VII and IX

Ophthalmic Nerve (V1 )

• sensory: touch, pain, temperature, and proprioceptive information from the

conjunctiva, cornea, eye, orbit, forehead, ethmoid, and frontal sinuses

• traverses superior orbital fissure

•

• Branches

- Lacrimal n. carries sensory information from the lateral part of the upper eyelid,

conjunctiva, and lacrimal gland

- Frontal n.:

! supraorbital n. : sensory from the forehead and scalp

! supratrochlear n.: sensory from the bridge of the nose, medial part of the upper

eyelid and medial forehead.

- Nasociliary n.: Branches go to eyeball, nasal cavity and external nose.

! infratrochlear n.: sensory to skin of upper eyelids, lacrimal sac, and side of nose

! posterior ethmoidal n.: sensory from

post. ethmoidal air cells and

sphenoid sinus

! anterior ethmoidal n.: sensory from

the internal and external nose.

Supplies anterior ethmoidal cells and

then enters anterior fossa of cranium.

Supplies mucosa of anterior portion

of the nasal septum with the external

nasal branch supplying sensory to

skin on lower 1/2 of nose

! long ciliary nn.: pierce sclera around

optic n., and are sensory to eyeball

(e.g., cornea and sclera)

! short ciliary nn.: pierce sclera around

optic n., and are sensory to eyeball.

Carry post ganglionic fibers from

CN III

7

GA 807

GA 808

• Clinical Test: Corneal reflex with wisp of

cotton. Prick forehead with pin (pain),

apply warm and cold objects

(temperature).

Maxillary Nerve (V2 )

• purely sensory: maxilla and overlying

skin, nasal cavity, palate, nasopharynx

and meninges of the anterior and

middle cranial fossae

• traverses cavernous sinus and leaves

middle cranial fossa through the

foramen rotundum

- enters pterygopalatine fossa,

leaves through pterygomaxillary

fissure

- in the pterygopalatine fossa it is

associated with pterygopalatine

ganglia (part of CN VII) which is

suspended from the maxillary

division

• Branches:

- Zygomatic n. :

! Divides into

zygomaticofacial and zygomaticotemporal nn. for sensation of temporal and

zygomatic regions

! Communicating branch to lacrimal gland

- Posterior Superior Alveolar n.:

! Sensory from mucous membrane of the cheek and the adjacent gingiva as well as

the maxillary sinus, and the molar teeth.

- Infraorbital Nerve: from maxillary nerve and enters the floor of the orbit. Emerges

through infraobital foramen

! Branches: supply maxillary teeth, lower eyelid, side of the nose, and upper lip.

Pharyngeal n. : sensory to pharynx

- Greater palatine n.: travels palatine canals and is sensory to the hard palate

- Lesser Palatine n.: travels palatine canals and is sensory to the soft palate

- Nasopalatine n.: travels sphenopalatine foramen and is sensory to anterior region of hard

palate and septum of nose

- Nasal branches: nasal cavity

8

GA 810

GA 811

• Clinical Test: Stroke sensory zone of V2 as described above for V1

Mandibular Nerve (V3)

• Sensory: meninges, mandibular skin

(except angle and poster ramus area),

skin of temporal region, lower lip,

mandibular teeth and gingiva

• Motor (branchial): mm. of

mastication plus, ant. belly of

digastric, mylohyoid m., tensor veli

palatini m., tensor tympani m.

• Traverses middle cranial fossa and

passes through foramen ovale

• (Branchio)Motor Branches:

- Named branches to mm. of

mastication (n. to temporalis,

pterygoids, masseter)

- N. to mylohyoid (also supplies ant. digastric): branches from inferior alveolar n.

- N. to tensor tympani (see later in ear)

- N. to tensor veli palatini (see later in oral cavity, palate)

• General Sensory Branches:

- Lingual n.

! Sensory innervation from the

mucous membrane of the

anterior 2/3 of tongue, the

lingual gingiva, and other

structures adjacent to the

tongue

! Joined by chorda tympani- a

branch of CN VII (taste ant.

2/3 tongue,

parasympathetics)

! Carries parasympathetic

fibers (from CN VII) to

submandibular and

sublingual glands

Inferior alveolar n.

! Sensory and motor

! Before entering the mandibular foramen it gives motor branches to mylohyoid

muscle, and anterior belly of the digastric muscle

! After entering the mandibular foramen is only sensory to the mandibular teeth and

gingiva, chin and lower lip. Exits mandible as mental nerve.

9

- Auriculotemporal n.

! Sensory to temporal region and TM joint

! encircles middle meningeal artery

! Carries postganglionic parasympathetic axons (secretomotor) from otic ganglion to

parotid gland.

• Clinical Test: Stroke sensory zone for sensory component. For the motor component, ask

patient to clench jaws, open and move jaw side to side against mild resistance. Compare

muscle strength from side to side.

CN

Name

Sensory

Special General Visceral

Motor

Somatic Branchial

Parasym

pathetic

V Trigeminal * *

Sketch CN V

MA = Moore, Agur, and Dalley. 2011. Essential Clinical Anatomy (4th Ed), Lippincott Williams & Wilkins

MD = Moore, KL and Dalley, A. 2006. Clinically Oriented Anatomy (5th Ed), Lippincott Williams & Wilkins

GD = Tank, PW. 2005. Grant’s Dissector (13th Ed), Lippincott Williams & Wilkins

GA = Agur AMR and Dalley, A 2005. Grant’s Atlas of Anatomy (11th Ed), Lippincott Williams & Wilkins

N = Netter, FH. 2011, Atlas of Human Anatomy (5th Ed), Saunders Elsevier OR Netter Presenter ICON System

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