5.1.1 Cranial Nerve V

Question 1

What fibres does the trigemnial nerve have?

Answer 1

General sensory and motor

Question 2

What are the 3 branches of the trigeminal nerve?

Answer 2

Va-Opthalmic (sensory)
Vb-Maxillary (sensory)
Vc-Mandibular (motor and sensory)

Question 3

What do branches of the trigemnial nerve supply?

Answer 3

• Skin and tissues of the face
• Portion of scalp
• Deep facial structures
• Anterior 2/3rds of the tongue (general sensation NOT TASTE)
• Muscles of mastication- Vc

Question 4

What reflex arc does the trigeminal supply?

Answer 4

Corneal reflex
Very light touch of cornea, detected by CNVa, afferent eyelid closed by CNVII via orbicularis oculi efferent

Just think afferent is arriving, so first thing that happens, which is sensation which is detected by CNVa

Question 5

How do you examine the trigeminal nerve?

Answer 5

Light touch each side of Va,b and c to see if it’s the same each side or no sensation

Muscles of mastication

Corneal reflex

Question 6

What clinical findings can present suggesting underlying pathology?

Answer 6

• Sensory deficits within dermatomal regions
• Weakness in muscles
• Absent corneal reflex

Question 7

What clinical conditions can involve the trigeminal nerve?

Answer 7

• Trigeminal herpes zoster (shingles, reactivation of VZ in trigeminal ganglion)
• Trigeminal neuralgia (compression from aberrant blood vessel-irregular bend in blood vessel)- leads to severe sharp shooting pain in the dermatome
• Orbital and mandibular fractures
• Posterior cranial fossa tumours

Question 8

What is particularly concerning in trigeminal shingles?

Answer 8

Involvement of either the cornea or conjuctiva which can be sight threatening

Question 9

Outline the pathway of the intracranial branches of the trigemnial nerve

Answer 9

Question 10

What are the major branches of CNVa and what areas do these branches supply?

Answer 10

• Frontal nerve- supraorbital and supratrochlear to supply the forehead
• Nasociliary nerve- supplies sensory to eye & tip of nose
• Lacrimal- supplies lacrimal glands frontal supplying forehead

Question 11

What are the major branches of CNVb and what areas do these branches supply?

Answer 11

• Infra-orbital nerve- vulnerable in orbital floor fracture Runs within bone forming floor of orbit if damaged can lead to sensation loss below orbit
• Superior alveolar nerves- supplies upper teeth and gums

Question 12

What are the major branches of CNVc and what areas do these branches supply?

Answer 12

• Auriculotemporal nerve- sensory to scalp, external ear and TMJ
• Lingual nerve- general sensation from anterior 2/3 tongue
• Inferior alveolar nerve- supplies lower teeth and gums
• Mental nerve (+inferior alveolar susceptible in mandibular fractures)

Question 13

Outline route of 3 branches (AGAIN)

LEARN

Answer 13

Opthalmic
1. Pons
2. Trigemnial ganglion
3. Cavernous sinus (lateral wall association)
4. Superior orbital fissure
5. Branches into lacrimal, nasocilliary and frontal branches

Maxillary
1. Pons
2. Trigemnial ganglion
3. Cavernous sinus (lateral wall association)
4. Foramen rotundum
5. Branches into infra-orbital and superior alveolar nerves

Mandibular
1. Pons
2. Trigemnial ganglion
3. Foramen ovale
4. Branches into auriculotemporal, lingual, inferior alveolar and mental nerves

LEARN

LEARN

Question 14

What is Hutchinson’s sign?

Answer 14

Trigemnial shingles-
Vesicles on the tip of the nose, this means that the nasociliary branch is affected, which is a branch of the opthalmic nerve

This nerve branch is the dermatome which contains the eye thus SIGHT THREATENING

Question 15

What does the mental nerve become?

Answer 15

Enters into mandibular canal, becomes inferior alveolar nerve running within mandible

Damaged in mandibular fractures