Deck 2: Trigeminal Nerve

Which cranial nerves attach to the forebrain?

CN I (Olfactory)

CN II (Optic)

Which cranial nerves attach to the brainstem?

CN III to CN X (CN III, IV, V, VI, VII, IX, X)

CN XII

Describe the course of CN XI (Spinal accessory) nerve. 

1. Emerges from the cervical spinal cord

2. Ascends through foramen magnum

3. Exits via the jugular foramen

Which cranial nerve is the only one to emerge from the dorsal surface of the brainstem?

CN IV (Trochlear)

What cranial nerves does the CN V (Trigeminal nerve) travel in close proximity to?

CN III, IV & VI

What type of innervation does the Trigeminal nerve have? Sensory, motor or both?

Both!

• Somatic sensory nerve - for the face 

• Somatic motor nerve - for the muscles of mastication + other small muscles

Where does the trigeminal nerve (CN V) emerge, and what are the two roots?

 → emerges from the lateral surface of the pons of the midbrain via 2 roots

1. Large sensory root

2. Small motor root

How are the branches of the trigeminal nerve (V1, V2, V3) formed?

Sensory and motor root fuse → trigeminal ganglion (Gasserian ganglion, semilunar ganglion) → V1 (Ophthalmic) + V2 (Maxillary) + V3 (Mandibular) arise

Do the sensory and motor roots synapse on the trigeminal ganglion?

No it does NOT synapse at the ganglion

What does the ganglion contain?

has cell bodies of somatic sensory neurons

What type of innervation does V1, V2 and V3 have?

V1 and V2 - only sensory

V3 - sensory and motor

Trace the path of V1, V2 and V3.

V1 → cavernous sinus → superior orbital fissure → orbit

V2 → cavernous sinus → foramen rotundum → pterygopalatine fossa

V3 → foramen ovale → infratemporal fossa

Does V3 pass through the cavernous sinus?

No, only V1 anD 

Which cranial openings do V1, V2, V3 travel through?

V1 (and CN III, IV, VI) → Superior orbital fissure

V2 → Foramen rotundum

V3 → Foramen ovale

What sensory nerve branches of the trigeminal nerve (CN V) emerge onto the face, and from which skull foramina do they exit?

V₁ → Supraorbital nerve → exits through the supraorbital foramen/notch

V₂ → Infraorbital nerve → exits through the infraorbital foramen

V₃ → Mental nerve → exits through the mental foramen

Which nerves provide sensory innervation to the posterior scalp and neck?

spinal nerves (C2 & C3)

Why is C1 not shown providing sensory innervation to the scalp or face? What happened to C1?

C1 does not provide sensory innervation to the face or scalp

What is the main sensory nerve of the face and anterolateral scalp?

Trigeminal Nerve = main sensory nerve of the face and anterolateral scalp

What areas does the ophthalmic division (V1) innervate?

Skin of the:

• anterior forehead

• upper eyelids

• anterior nose

What areas does the maxillary division (V2) innervate?

Skin of the:

• lower eyelid

• cheek

• lateral nose

• upper lip

What areas does the mandibular division (V3) innervate?

Skin of the:

• lower face along the mandible

• lower lip

• lateral forehead near the temples

• part of the auricle

How are cutaneous nerve branch names determined?

descriptive of their location (foramen) and the skin area/region they innervate

All 3 divisions (V1, V2 & V3) are associated with ____________ ganglia and help distribute _______________ fibers to their targets.

All 3 divisions (V1, V2 & V3) are associated with parasympathetic ganglia and help distribute parasympathetic fibers to their targets.

List 4 parasympathetic ganglia. Name where this ganglia is located and which CNV division is associated with it.

Describe the synapse that occurs at the Ciliary ganglion. 

1. Preganglionic PNS fibers from CN III synapse onto ciliary ganglion

2. Postganglionic PNS fibers are conveyed via short ciliary nerves to pupillary sphincter & ciliary muscles

Describe the synapse that occurs at the Pterygopalatine ganglion. 

Preganglionic PNS fibers from CN VII synapse onto pterygopalatine ganglion

• involved with innervating the lacrimal gland & mucous glands of the nose and palate

Describe the synapse that occurs at the Otic ganglion. 

Preganglionic PNS fibers from CN IX synapse

• involved with innervating the parotid gland

Describe the synapse that occurs at the Submandibular ganglion. 

Preganglionic PNS fibers from CN VII synapse

• involved with innervating the sublingual and submandibular glands

List all the regions the CN V₁ provides sensory innervation to.

• Skin of anterior scalp & forehead, upper eyelid & anterior nose

• Orbit, cornea, superior palpebral & bulbar conjunctiva

• Mucous membranes of anterior nasal cavity & paranasal sinuses (frontal, ethmoid & sphenoid)

• Dura of anterior cranial foss

What is the role of CN V1 in the corneal reflex?

CN V1 is the sensory limb of the corneal reflex

• this is a key brainstem reflex used clinically to test the integrity of this division

After the passing superior orbital fissure, the V1 divides into 3 branches. What are they?

1) Frontal nerve

• Runs superior

2) Nasociliary nerve

• Runs medially towards the nose

3. Lacrimal nerve

• Runs laterally

What does the frontal nerve divide into? What do these nerves supply?

1) Supra-orbital

2) Supratrochlear

→ supply the superior eyelid, scalp & forehead

What is the nasociliary nerve? What does it supply?

→ sensory nerve to the eyeball

• also supplies several branches to the orbit, paranasal sinuses, nasal cavity & dura mater of anterior cranial fossa

What does the nasociliary nerve divide into? What do these nerves supply?

1) Infratrochlear nerve 

• supplies the eyelids, conjunctiva, skin of the nose & lacrimal sac

2) Anterior  3) Posterior ethmoidal nerves

• supply the mucous membranes of the sphenoidal and ethmoidal sinuses, nasal cavities & dura mater of the anterior cranial fossa

4) Long ciliary nerve

• supplies the iris and cornea

• conveys postsynaptic SNS fibers to the dilator pupillae

What’s the significance of the postsynaptic SNS fibers to the dilator pupillae?

these post-synaptic SNS fibers →  sensory limb of corneal reflex

Describe the course of the lacrimal nerve. What does it supply?

→ courses superolaterally to the lacrimal gland

• supplies the conjunctiva & skin of upper eyelid

• its distal part carries secretomotor fibers conveyed to it from ‘hitchhiking’ on the zygomatic nerve (CN V2) via a communicating branch

What are the characteristics of the Corneal reflex?

→ refers to the contraction of the o.oculi in response to light touch of the cornea

• direct & consensual response

• present at infancy (works on anyone — whether you’re disabled or in coma)

• reflex may be slowed or absent in many disorders affecting the ophthalmic nerve, trigeminal ganglion, or brain stem nuclei

What are the afferent and efferent limbs of the corneal reflex?

Afferent - nasociliary branch of the ophthalmic nerve (V1) → detecting the stimuli

Efferent - Facial nerve (CN VII) → closure of eye

What is Herpes Zoster Ophthalmicus (HZO)?

→ viral disease causing a unilateral, painful skin rash

• occurs when the virus travels through trigeminal nerve dermatomes including areas shared by the eye and ocular adnexa

  

What is Zoster Keratitis/Keratouveitis? Why is it an ocular emergency?

• occurs in ~50% of HZO cases

• Ocular findings include conjunctivitis, uveitis, episcleritis, keratitis, and retinitis

• it’s an ophthalmologic emergency b/c delayed treatment → vision loss

List all the regions the CN V₂ provides sensory innervation to.

• Skin of midface: lower eyelid, cheek, lateral nose, upper lip

• Mucous membranes of the postero-inferior nasal cavity, maxillary sinus, hard and soft palate, superior oral vestibule

• Maxillary teeth

• Dura of middle cranial fossa

What is the MAJOR sensory nerve of the maxillary region & mid face?

V2

Maxillary nerve (CN V2) divides into 6 major branches. What are they?

1. Zygomatic

2. Infraorbital

3. Superior alveolar

4. Greater palatine

5. Lesser palatine

6. Nasopalatine 

Maxillary nerve (CN V2)

What does the Zygomatic (zygomaticofacial and zygomaticotempora) nerves supply?

• skin of the prominence of the cheek and anterior part of temporal fossa

  • sends communicating branch to lacrimal nerve to distribute postganglionic parasympathetic motor fibers to lacrimal gland & mucous glands of the nose & palate

Maxillary nerve (CN V2)

What does the Infraorbital nerve supply?

• skin and conjunctiva of the lower eyelid, cheek, lateral nose, and upper lip

  • ends in the infraorbital foramen to supply the dermatomes of the face

• mucosa of the superior oral vestibule and antero-inferior nasal septum

Maxillary nerve (CN V2)

What does the Superior alveolar nerve supply?

maxillary sinus

maxillary teeth

Maxillary nerve (CN V2)

What does the Greater Palantine nerve supply?

mucosa & glands of the hard palate

Maxillary nerve (CN V2)

What does the Lesser Palantine nerve supply?

mucosa & glands of the soft palate

Maxillary nerve (CN V2)

What does the Nasopalatine nerve supply?

mucosa of the anterior part of the hard palate & nasal septum

Of all the nerve branches of the Maxillary nerve (V2), which ones distribute postganglionic parasympathetic fibers from the Pterygopalatine ganglion?

1. Zygomatic

2. Greater palatine 

3. Less palantine

4. Nasopalantine

List all the regions the CN V3 provides sensory innervation to.

• Skin of the lower face along the mandible, lower lip, lateral forehead near the temples, part of auricle

• Mucous membranes of floor of mouth, inferior oral vestibule, anterior 2/3 tongue

• Mandibular teeth

• TMJ

• Dura of middle cranial fossa

List all the regions the CN V3 provides motor innervation to.

• 4 Muscles of mastication

• 2 oral floor muscles

• 1 tensor muscle of the middle ear

• 1 tensor muscle of the palate

Mandibular nerve (CN V3) divides into 5 major sensory branches. What are they?

1. Auriculotemporal

2. Inferior Alveolar

3. Mental

4. Lingual

5. Buccal 

Of all the nerve branches of the Mandibular nerve (V3), which ones distribute postganglionic parasympathetic fibers from the Otic & Submandibular ganglion?

1. Auriculotemporal

2. Lingual

Of all the nerve branches of the Mandibular nerve (V3), which ones distribute postganglionic taste fibers from the Otic & Submandibular ganglion?

Lingual

Mandibular nerve (CN V3) divides into 4 major motor branches that supply the muscles of mastication. What are they?

1. Masseter

2. Temporalis

3. Medial pterygoid

4. Lateral pterygoid
   (each is the “nerve to ___ muscle”)

Mandibular nerve (CN V3) divides into 2 major motor branches that supply the 2 oral muscles. What are they?

• mylohyoid

• anterior belly of the digastric

Mandibular nerve (CN V3)

What nerve supplies the mylohyoid & anterior belly of the diagastric?

mylohyoid nerve

Mandibular nerve (CN V3)

Mandibular nerve (CN V3) divides into 2 major motor branches that supply the 2 tensors. What are they?

Tensor tympani (middle ear)

Tensor veli palatini (palate)

Where are many of the motor branches of V3 located?

infratemporal fossa

What is trigeminal neuralgia and what are its key features?

• Most common disorder of CN V

  • Usually affects V2 or V3 (less often V1)

• occurs due to vascular compression of the sensory root near the brainstem

• Causes recurring, severe, electric-shock–like stabbing pain in trigeminal nerve distributions

• Triggers = eating, talking, shaving, or light touch