Session 8 - Cranial Nerves and Assessment of Function Flashcards
Which PA is CN V a derivative of?
1st PA
What is the sensory innervation of CN V
skin, mucous membranes, and sinuses of face
What is the motor innervation of CN V?
mandibular branch innervates muscles of mastication as well as anterior belly of digastric, tensor veli palatine, and tensor tympani
What is the relationship of parasympathetic ganglia and CN V?
post ganglionic neurones of PS ganglia travel WITH but NOT part of trigeminal nerve
Where is the trigeminal ganglion found?
middle cranial fossa
Lateral to cavernous sinus in a depression in temporal bone known as trigeminal cave
What is a nucleus and a ganglion with relation to nerves?
Nucleus – collection of nerve cell bodies WITHIN CNS
Ganglion – collection of nerve cell bodies OUTSIDE CNS
What is the name of V1, V2, and V3?
V1 – ophthalmic.
V2 – Maxillary.
V3 – Mandibular
Through which foramen do the ophthalmic and maxillary nerves travel?
Ophthalmic - superior orbital fissure
Maxillary - foramen rotundum
Through which foramen does the mandibular nerve travel through?
foramen ovale
What nerves does the ophthalmic nerve give rise to?
frontal, lacrimal, nasociliary
What sensory structures does the ophthalmic innervate?
Innervate skin and mucous membrane derivatives of the frontonasal prominence:
- Forehead and scalp
- Frontal and ethmoidal sinus
- Upper eyelid and its conjunctiva
- Cornea
- Dorsum of nose
Describe the PS supply of the lacrimal gland
Post ganglionic fibres from pterygopalatine ganglion travel with the zygomantic branch of V2 and then join the lacrimal branch of V1. These fibres supply PS innervation to lacrimal gland
What is the corneal reflex? What nerves are involved and what is an absent reflex indicative of?
- Involuntary blinking of eyelids stimulated by stimulation of cornea
- Ophthalmic nerve acts as afferent limb, facial nerve is the efferent limb.
- If reflex absent à sign of damage to the trigeminal/ophthalmic nerve or facial nerve.
Which PA is maxillary derived from?
1st PA
What structures does the maxillary innervate?
derivatives of maxillary prominence of 1st PA:
- Lower eyelid and its conjunctiva
- Cheeks and maxillary sinus
- Nasal cavity and lateral nose
- Upper lip
- Upper molar, incisor , and canine teeth and associated gingiva
- Superior palate
What nerves does the mandibular nerve give rise to?
Gives rise to buccal, inferior alveolar, auricotemporal, and lingual nerve
What sensory structures does the mandibular innervate?
Derivatives of mandibular prominence of 1st PA:
- Mucous membranes and floor of oral cavity
- External ear
- Lower lip
- Chin
- Anterior 2/3rds of tongue (only general sensation)
- Lower molar, incisor, and canine teeth and associated gingiva
What motor structures does the mandibular nerve innervate?
- Muscles of mastication
- Anterior belly of digastric muscle
- Tensor veli palatine
- Tensor tympani
What is the PS supply of the mandibular nerve?
- Submandibular and sublingual glands
- Parotid gland
Where does the inferior alveolar nerve travel through?
Mandibular foramen and mandibular canal.
What clinically relevant structures does the inferior alveolar nerve innervate?
inferior alveolar nerve forms the inferior dental plexus which innervates the lower teeth
Why is the inferior alveolar nerve blocked for some dental procedures? Where is it blocked? Where is anaesthetic administered?
- Inferior alveolar nerve blocked for some dental procedure, before it gives rise to plexus
- Anaesthetic administered at mandibular fossa.
How would you test the sensory supply of the trigeminal nerve?
Patient closes eyes and you introduce a cotton wisp to areas of face supplied by trigeminal nerve
How would you test the motor supply of the trigeminal?
- Ask patient to clench jaw as you palpate temporalis and then repeat palpating inferiorly for masseter
- Ask patient to open their mouth and deviate their mandible right and left, checking for competence of medial and lateral pterygoid muscles.
How would you test the corneal reflex? What nerves is it checking for?
- Requires competent ophthalmic branch and temporal and zygomatic branches of facial nerve
- Cotton wisp on eye.
What motor structures does CN III innervate?
extraocular muscles
What structures do the PS and sympathetic nerves that run with CN III innervate?
PS – supplies sphincter pupillae and ciliary muscles of eye
Sympathetic – runs with oculomotor nerve to innervate superior tarsal muscle
Where does CN III originate from?
anterior aspect of midbrain
Describe how CN III enters the cavernous sinus. What happens here?
Nerve pierces dura mater and enters lateral aspect of cavernous sinus. Receives sympathetic branches from internal carotid plexus in cavernous sinus
How does cn III leave the cranial cavity? What happens after it leaves?
Nerve leaves cranial cavity via superior orbital fissure. Then divides into superior and inferior branches.
What structures does the superior branch of oculomotor nerve supply?
motor innervation to superior rectus and levator palpabrae superioris. Sympathetic fibres run with superior branch to innervate superior tarsal muscle
What structures does the inferior oculomotor nerve supply?
motor innervation to inferior rectus, medial rectus, and inferior oblique. PS fibres to the ciliary ganglion which innervates sphincter pupillae and ciliary muscles
What is the actions of the superior rectus and LPS and superior tarsal?
Superior rectus – elevates eyeball
Levator palpabrae superioris – raises upper eyelid
Superior tarsal - keeps eyelid elevated after LPS has raised it
What is the action of the inferior rectus, medial rectus and inferior oblique?
Inferior rectus – depresses eyeball
Medial rectus – adducts eyeball
Inferior oblique – Elevates, abducts, and laterally rotates eyeball
Which muscles do the superior and inferior oculomotor supply?
Superior - superior rectus, LPS, superior tarsal (sympathetic)
Inferior - inferior rectus, medial rectus, inferior oblique
What structures get PS innervation from oculomotor? What is their function? Which branch of cn III has a PS supply?
Sphincter pupillae – constricts pupil and reduces amount of light entering eye
Ciliary muscles – contracts, causes lens to become more spherical, and more adapted to short range vision
Inferior
What are 3 anatomical causes of an oculomotor nerve lesion?
Increases intracranial pressure – compresses nerve against temporal bone
Aneurysm of posterior cerebral artery
Cavernous sinus infection or trauma
What is the result of an oculomotor nerve lesion?
Ptosis due to paralysis of LPS
Eyeball resting in down and out position due to paralysis of superior, inferior, medial rectus
Dilated pupil due to unopposed action of dilator pupillae muscle
Why can a fracture of the cribiform plate lead to a runny nose?
CSF fluid leaking out of nose
Why can a tumour of the middle ear cause abnormal sensation in taste?
compression of facial nerve by tumour can damage chorda tympani branch that supplies special taste sensation to anterior 2/3rds of tongue
What is the levator glandulae thyroideae?
fibrous band which connects istthmus of thyroid gland to hyoid bone
Why does the thyroid gland move during swallowing?
fascia of thyroid gland attached to thyroid and cricoid cartilages
Why is the inferior thyroid artery tortuous?
thyroid gland ascends when swallowing. Tortuous to allow the artery to ascend with thyroid gland
What can be found at the C6 landmark?
- pharynx and oesophagus junction
- carotid artery palpation site
- middle cervical sympathetic ganglion
What is the function of the carotid body and carotid sinus? Where are they located?
Carotid body - chemoreceptor, oxygen levels, part of artery
Carotid sinus - baroreceptor, pressure levels, outside artery
What nerve supplies the carotid sinus and body?
glossopharyngeal nerve and vagus
How would you distinguish the ECA from the ICA in a carotid arteriogram?
ICA gives no branches in the neck
What nerves can be damaged in the neck?
vagus and sympathetic cervical chain
