Nerves of the H&N CN I-VI Flashcards
What are the different cranial nerves
CN I - olfactory
CN II - optic
CN III - oculomotor
CN IV - trochlear
CN V - trigeminal
CN VI - abducens
CN VII - facial nerve
CN VIII - vestibulocochlear nerve
CN IX - glossopharyngeal nerve
CN X - vagus nerve
CN XI - spinal accessory nerve
CN XII - hypoglossal nerve
What are the branches of the trigeminal nerve and what are their functions
Opthalmic (V1) - sensory
Maxillary (V2) - sensory
Mandibular (V3) - motor and sensory
What are the cranial nerves
Nerves that are part of the periphernal nervous system that arise at irregular intervals from CNS segments
Can be general sensory, special sensory, motor and/or autonomic
Where do the cranial nerves branch from
Two from forebrain
Two from midbrain
Four from pons
Four from medulla
Describe the course of the olfactory nerve
Originates in roof of nasal cavity
Fibres run through cribriform foramina to enter olfactory bulb
Olfactory fibres then form olfactory tract which goes to the temporal lobe
What are the functions of the olfactory nerve and how do you test the functions
Olfaction is its function
Test changes/differences in smell and test changes in taste (taste affected by smell)
Test one nostril at a time
Describe the course of the optic nerve
Cells within retina generate impulses in response to light
Impulse generates AP which is propagated along optic nerve
Optic nerve exits back of orbit via optic canal where fibres cross and merge at the optic chiasm
Fibres then enter optic tract
AP runs along visual pathway to reach primary visual cortex
What can happen to the optic nerve if there is raised ICP
Optic disc can swell as the optic nerve carries an extension of the meninges
Optic disc swelling = papilloedema
How do you test the optic nerve
Visual acuity tests - e.g.
- Snellen chart
- Check visual fields
- Test pupillary responses
Describe the course of the oculomotor nerve
Originates in anterior midbrain
Runs through lateral wall of cavernous sinus
Runs through superior orbital fissure
What are the functions of the oculomotor nerve
Motor functions:
- Innervates most muscles that move the eyeball - extra-ocular muscles
- Innervates muscles of the eyelid - levator palpebrae superioris
PNS functions:
- Innervates sphincter pupillae - constricts pupil
- Innervates ciliary muscles - surround lens
Where is the oculomotor at most risk of compression
Between tentorium cerebelli and part of the temporal lobe
Due to raised ICP
How do you test oculomotor functions
Inspect eyelids and pupil size - see if pupil is normal or if it is blown
Test eye movements and pupillary reflexes
History of diplopia
Look for down and out position
Look for ptosis
Describe the course of the trochlear nerve
Originates from the back of the midbrain
Goes through the lateral wall of the cavernous sinus
Runs through superior orbital fissure
What is the function of the trochlear nerve and how do you test it
Innervates superior oblique muscle - moves the eyeball
Test eye movements to test the nerve
Describe the course of the trigeminal nerve and its branches
Trigeminal nerve originates in the pons then forms the trigeminal ganglion and splits into:
- Opthalmic division - after ganglion, passes through lateral wall of cavernous sinus -> superior orbital fissure -> orbit
- Maxillary division - after ganglion, passes through lateral wall of cavernous sinus -> foramen rotundum and then pterygopalatine fossa
- Mandibular division - after ganglion, passes through foramen ovale -> infratemporal fossa
How do you test the trigeminal nerve
Test sensation in each of its dermatomes
Test muscles of mastication - jaw jerk
Test corneal reflex
Which branches of the opthalmic division are vulnerable to damage
Supraorbital and supratrochlear - sensory innervation to forehead and anterior scalp
Which branches of the maxillary division are vulnerable to damage
Infraorbital - runs through floor of orbit -> susceptible to injury in orbital floor #
Superior alveolar nerve
Which branches of the mandibular division are vulnerable to damage
Inferior alveolar - runs through bony canal in mandible -> susceptible to injury in mandibular #
Lingual
Auriculotemporal
What are the symptoms of trigeminal neuralgia
Episodes of sharp shooting pains throughout the trigeminal dermatomes
Usually only one side of the face
Describe the course of the abducens nerve
Originates in lower pons - junction between pons and medulla
Runs inwards before passing into cavernous sinus
Runs through superior orbital fissure to enter orbit
What is the function of the abducens nerve
Innervates lateral rectus muscle - abducts the eye
What is abductor nerve palsy
Where the abducens nerve has been compressed and so the patient cannot look laterally - cannot abduct the eye
