Lecture 8- CN V - the trigeminal nerve Flashcards
arises from the
pons- side miday down
- Target tissues:
- Skin
- Face
- Deep facial structures (e.g. nose)
- scalp
type of innervation
motor and genral snesory
- not taste or smell
- but pain
- Testing the trigeminal area
- Light touch va (ophthalmic), Vb (maxillary) and Vc (mandibular division) dermatomes
- Ask to demonstrate muscles of mastication
- Corneal reflex
special reflex which tests opthalmic division
- Touch surface of the eye (felt by ophthalmic division of trigeminal nerve)- triggers reflex which makes the eye blink
- Orbicularis oculi muscle
Va
opthalmic
Vb
maxillary
Vc mandibular
Va- opthalmic
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
Vb- maxillary
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
Vc mandibular
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
- If lesions
- 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)
- Sensory deficits within the dermatomal regions
interesting related clinical conditions
- 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
CN V -Trigeminal nerve route
- Trigeminal nerve has an extensive nuclei that runs the whole length of the brainstem
- Comes out at level of the pons
- Trigeminal ganglion that splits into:
- Va- ophthalmic
- Pass through walls of cavernous sinus
- Passes through the superior orbital fissure into the orbit
- Gives other branches
- Vb- maxillary
- Pass through walls of cavernous sinus
- Passes through the foramen rotundum into the pterygoid palatine fossa
- Nasal cavity, nose etc
- Vc- mandibular
- Doesn’t pass through sinus – more lateral rout
- Passes through foramen ovale
- Bring it into the infratemporal fossa
- Muscles of mastication e.g. pterygoid
- Va- ophthalmic
- why it covers such a broad part of the face?
Extensive distal branches- why
distal branches of Va
Nasociliary nerve
Frontal nerve
Lacrimal nerve
distal branches of Vb
BranchesMiddle meningeal nerve
Zygomatic nerve
Pterygopalatine nerves
Branches for the nasal cavity
Palatine nerves
Posterior superior alveolar nerves
Infraorbital nerve
distal branches of Vc
Deep temporal nerve
Nerve to the medial pterygoid muscle
Nerve to the lateral pterygoid muscle
Masseteric nerve
Nerve to the tensor veli palatini muscle
opthalmic nerve is purely
sensory
route of the opthalmic
- Runs from the pons through the cavernous sinus and through the superior orbital fissure into the orbit
frontal nerve of Va
runs up onto the forehead and scalp
- Nasocillary N. of Va
- Structures in front of the eye and other eye structures e.g. opthalmic shingles
- Tip of the noes
Rash and crusting on noes
Hutchinson sign – presence of rash on tip of noes is a warning that the eye is at risk- opthalmic shingles
maxiallary nerve is purely
sensory
route of maxillary nerve
- 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
- Infraorbital N of Vv
- 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
-
Superior alveolar nerves of Vb
*
- Sensory info from the top teeth and gums
- Comes of the infraorbital nerves
- Also vulnerable to infraorbital floor fractures
mandibular nerves are both
- Sensory and motor nerves
route of the mandubular branch
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
auricular temporal nerve of Vc
ear and temple
- Lingual nerve of Vc
anterior two-thirds of the tongue
- Inferior alveolar nerve of vc
- 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
