Lecture 8- CN V - the trigeminal nerve

Question 1

arises from the

Answer 1

pons- side miday down

Question 2

• Target tissues:

Answer 2

• Skin
• Face
• Deep facial structures (e.g. nose)
• scalp

Question 3

type of innervation

Answer 3

motor and genral snesory

• not taste or smell
• but pain

Question 4

• Testing the trigeminal area

Answer 4

• Light touch va (ophthalmic), Vb (maxillary) and Vc (mandibular division) dermatomes
• Ask to demonstrate muscles of mastication
• Corneal reflex

Question 5

special reflex which tests opthalmic division

Answer 5

• Touch surface of the eye (felt by ophthalmic division of trigeminal nerve)- triggers reflex which makes the eye blink
• Orbicularis oculi muscle

Question 6

Va

Answer 6

opthalmic

Question 7

Vb

Answer 7

maxillary

Question 8

Vc mandibular

Question 9

Va- opthalmic

Answer 9

The ophthalmic branch is the first division of the trigeminal nerve. It is a purely sensory nerve that carries afferent stimuli of pain, light touch, and temperature from the upper eyelids and supraorbital region of the face, up to the upper surface of the head. The nerve also acts as a conduit for sympathetic fibers that require access to the ciliary body, lacrimal glands, cornea, and conjunctiva of the eye. Furthermore, the ophthalmic branch also carries fibers arising from the dura mater of the anterior cranial fossa, the frontal sinus, and the superior aspect of the nasal cavity.

Eyes, conjunctiva, lacrimal gland, nasal cavity, frontal sinus, ethmoidal cells, falx cerebri, dura mater of anterior cranial fossa, superior parts of tentorium cerebelli, upper eyelid, dorsum of nose, anterior part of the scalp

Question 10

Vb- maxillary

Answer 10

Like the ophthalmic branch, the maxillary division of the trigeminal nerve (CN V2) is a purely sensory entity that carries impulses from the midface. It has a middle meningeal branch that detects stimuli from the dura of the middle cranial fossa. Additionally, the zygomatic, pterygopalatine, and the posterior superior alveolar nerves unite at the opening of the foramen rotundum to form the maxillary branch of the trigeminal nerve.

Dura mater of the middle cranial fossa; mucosa of the nasopharynx, palate, nasal cavity, and nasopharynx; teeth and upper jaw; skin over the side of the nose, lower eyelid, cheek, and upper lip

Question 11

Vc mandibular

Answer 11

The last of the three trigeminal branches is the mandibular division (CN V3). As the largest component of CN V, it carries both sensory and motor stimuli. The motor branches correspond to the muscles that originated from the first pharyngeal arch. The sensory branches supply the lower third of the face, excluding the angle of the mandible (supplied by the second and third cervical segments). Although it carries sensory modalities from the mouth and gingiva, it does not carry special afferent stimuli (i.e. taste). However, the lingual nerve, which is a branch of CN V3 acts as a conduit for the chorda tympani (a branch of CN VII), which carries taste stimuli.

Buccal skin, anterior two-thirds of the tongue, temporal region; mastication muscles, mylohyoid muscle and anterior belly of the digastric muscle

Question 12

• If lesions

Answer 12

• • Sensory deficits within the dermatomal regions
    
    • Weakness of muscles of mastication (on affected side- if Vc involved)
    • Absent corneal reflex (CN Va is sensory part of the reflex)

Question 13

interesting related clinical conditions

Answer 13

• Trigeminal herpes zoster e.g. shingles (reactivation of VZ in trigeminal ganglion)= ophthalmic shingles
  
  • Can affect the surface of the eye- sight threatening
• Trigeminal neuralgia (compression of an aberrant blood vessel- sharp shooting face relating which branch of the trigeminal nerve is affected)
• Orbital and mandibular fractures (distal branches of CN V divisions)
• Posterior cranial fossa tumours
• Brainstem infarcts/ lesions in pons

Question 14

CN V -Trigeminal nerve route

Answer 14

1. Trigeminal nerve has an extensive nuclei that runs the whole length of the brainstem
2. Comes out at level of the pons
3. Trigeminal ganglion that splits into:
   
   1. Va- ophthalmic
      
      1. Pass through walls of cavernous sinus
      2. Passes through the superior orbital fissure into the orbit
      3. Gives other branches
   2. Vb- maxillary
      
      1. Pass through walls of cavernous sinus
      2. Passes through the foramen rotundum into the pterygoid palatine fossa
      3. Nasal cavity, nose etc
   3. Vc- mandibular
      
      1. Doesn’t pass through sinus – more lateral rout
      2. Passes through foramen ovale
      3. Bring it into the infratemporal fossa
         
         1. Muscles of mastication e.g. pterygoid

Question 15

• why it covers such a broad part of the face?

Answer 15

Extensive distal branches- why

Question 16

distal branches of Va

Answer 16

Nasociliary nerve
Frontal nerve
Lacrimal nerve

Question 17

distal branches of Vb

Answer 17

BranchesMiddle meningeal nerve
Zygomatic nerve
Pterygopalatine nerves
Branches for the nasal cavity
Palatine nerves
Posterior superior alveolar nerves
Infraorbital nerve

Question 18

distal branches of Vc

Answer 18

Deep temporal nerve
Nerve to the medial pterygoid muscle
Nerve to the lateral pterygoid muscle
Masseteric nerve
Nerve to the tensor veli palatini muscle

Question 19

opthalmic nerve is purely

Answer 19

sensory

Question 20

route of the opthalmic

Answer 20

• Runs from the pons through the cavernous sinus and through the superior orbital fissure into the orbit

Question 21

frontal nerve of Va

Answer 21

runs up onto the forehead and scalp

Question 22

• Nasocillary N. of Va

Answer 22

• Structures in front of the eye and other eye structures e.g. opthalmic shingles
• Tip of the noes

Question 23

Rash and crusting on noes

Answer 23

Hutchinson sign – presence of rash on tip of noes is a warning that the eye is at risk- opthalmic shingles

Question 24

maxiallary nerve is purely

Answer 24

sensory

Question 25

route of maxillary nerve

Answer 25

• Runs from the pons through the cavernous sinus and through the foramen rotundum into the front of the face via the pterygoid palatine fossa into the nasal cavity

Question 26

• Infraorbital N of Vv

Answer 26

• Through the floor the orbit- infraorbital foramen- to the front of the face
• Vulnerable to injury- e.g. floor fractures- test sensory function in the cheek

Question 27

• Superior alveolar nerves of Vb
  *

Answer 27

• Sensory info from the top teeth and gums
• Comes of the infraorbital nerves
• Also vulnerable to infraorbital floor fractures

Question 28

mandibular nerves are both

Answer 28

• Sensory and motor nerves

Question 29

route of the mandubular branch

Answer 29

Takes a slightly different route

Runs from the ganglion laterally to the cavernous sinus, leaves base of skull through the foramen ovale and get into the space called the infratemporal fossa. Lots of structures within this:

Pterygoid muscle

Branches of carotid artery

Question 30

auricular temporal nerve of Vc

Answer 30

ear and temple

Question 31

• Lingual nerve of Vc

Answer 31

anterior two-thirds of the tongue

Question 32

• Inferior alveolar nerve of vc

Answer 32

• Sensory info from the lower gum and teeth
• Runs through the bone of the mandible
• Then becomes the Mental nerve (comes through the mental foramen)
  
  • Skin on the chin