Cranial nerves Flashcards
The cranial nerves are covered with a sheath derived from?
Cranial meninges
What CN goes through the optic canal?
Optic nerve CN II
What CN go through the superior orbital fissure?
Oculomotor CN III
Trochlear CN IV
Abducens CN VI
Ophthalmic of trigeminal CN V
What CN goes through the foramen rotundum?
Maxillary of trigeminal CN V
What CN goes through foramen ovale?
Mandibular of trigeminal CN V
What CN goes through internal acoustic meatus?
Facial CN VII
Vestibulocohlear CN VIII
What CN goes through jugular foramen?
Glossopharyngeal CN IX
Vagus CN X
Accessory CN XI
What CNs come from the midbrain? pons? medulla?
midbrain: III & IV
pons: V
medulla: VI to XII
1st branchial arch
Trigeminal CN V
- mm. of mastication
- ant. of digastric, mylohyoid
- tensor tympani
- tensor veli palatini
2nd branchial arch
Facial CN VII
- mm. facial expression
- post. digastric, stylohyoid
- stapedius
3rd branchial arch
Glossopharyngeal CNIX
-stylopharyngeus
4th branchial arch
Vagus CNX and accessory CNXI (just cranial root)
-mm. palate, pharynx, larynx, sup. oesophag.
anosmia
loss of sense of smell
-old age, head injury, cribriform plate fractures, meningiomas in anterior cranial fossa
papillodema
increased intracranial pressure causes the part of the optic disc to swell
-compresses the central vein
Lesion of the right optic nerve causes what?
Right monocular blindness
can’t see out of right eye
Longitudinal lesion of the optic chiasm causes what?
Bitemporal hemianopsia (lost peripheral vision)
Lesion of the right optic tract causes what?
Left homonymous Hemianopsia (no left field of vision from both eyeballs)
What are the 4 extra-ocular muscles innervated by oculomotor nerve?
superior, medial, inferior rectus
inferior oblique
What is herpes zoster opthalmicus, and what does it have to do with cranial nerves?
- reactivation of the childhood chicken pox virus (varicella zoster) along the ophthalmic division of trigeminal
- vesicular rash or dermatitis
What is the relationship of the vagus CN and the major arteries?
it wraps under aorta on L side, and under subclavian on R side
Where does olfactory CN emerge from?
limbic lobe
Where are the cell bodies of olfactory CN?
olfactory epithelium
Clinical implications of olfactory CN
anosmia
olfactory halluciations
Where does optic CN emerge from?
primary visual cortex in occipital lobe (passing through visual area of thalamus first)
Where are the cell bodies of optic CN?
optic nerve (made of retinal ganglion and support cells)
Clinical implications of the optic CN
papiloderma
lesions of optic tract, nerve or chiasm
Where does the oculomotor CN emerge from?
midbrain –> lateral wall of cavernous sinus
Where are the cell bodies of the oculomotor nerve?
GSE- midbrain
GVE- midbrain and ciliary ganglion
What are the functions of the oculomotor CN?
GSE- 4 extra-oc. mm, levator palpabele superioris
GVE- sphincter pupillae, ciliary muscles
Clinical implications of oculomotor nerve
Eye will look towards week muscle
lazy eye
Where does the trochlear nerve emerge from?
dorsal midbrain -> pierces dura -> lateral wall of cavernous sinus
Where are the cell bodies of trochlear CN?
midbrain
Functions of the trochlear nerve?
GSE- super oblique moves eye down and out
Where does the trigeminal nerve emerge?
pons
Where are the cell bodies of trigeminal nerve?
trigemina ganglion (afferent) or pons (efferent)
Functions of trigeminal nerve?
GSA-
V1 (cornea, nasal cavity, scalp),
V2 (upper lip, teeth, gums, nose),
V3 (low lip, teeth, gums, anterior 2/3 tongue)
SVE- V3 (mastication, mylohyoid, ant. digastric, tensor veli palatini, tensor tympani)
Clinical implications of trigeminal nerve?
herpes zoster opthalmicus
Where does abducens nerve emerge from?
Pons-medula junction -> pierces dura -> through cavernous sinus
Where are the cell bodies of abducens nerve?
pons
Function of abducens
GSE- lateral rectus
Clinical implications of abducens nerve?
abducens palsy
Where does facial nerve emerge from?
pons-medulla junction
Where are the cell bodies of facial nerve?
SVE-pons
SVA-geniculate gnaglion
GVE-pons and pterygopalatine & submandibulat ganglia
What are the functions of the facial nerve?
GSA- ext. acoustis meatus
SVA- anterior 2/3 tongue
GVE- secretion of lacrimal, salivary, nasal mucous glands
SVE-facial expression, stapedius, post. digastric, stylohyoid
Clinical implications of facial nerve?
UMN lesion- contralateral lower face weakness
LMN lesion- ipsilateral whole face weakness
Functions of vestibulocochlear
SSA- balance and hearing
Clinical implications of vestibulocochlear nerve
vestibular neuritis
labyrinthitis
acoustic neuroma
Where does the glossopharyngeal nerve emerge from?
medulla
Where are the cell bodies of glossopharyngeal nerve?
medulla (SVE, GVE) optic ganglion (GVE) inferior ganglion (GSA, SVA) superior ganglion (GVA)
Functions of glossopharyngeal nerve
SVA- 1/3 tongue GSA-tonsils, post. 1/3 tongue, middle ear, GVA- carotid body and sinus GVE-salivary gland SVE- stylopharyngeus
Where does the vagus nerve emerge from?
medulla
Where are the cell bodies of vagus nerve?
medulla (SVE, GVE), in viscera (GVE), superior ganglion (GSA, GVA), inferior ganglion (SVA)
Functions of vagus nerve?
SVE: pharynx, larynx, palate, upper oseophag
GVE: cardiac and smooth mm.
GSA: auricle, external auditory meatus, post. dura mata
GVA: base tongue, pharynx, larynx, airways, heart, GIT
SVA: taste epiglottis and palate
Clinical implications of vagus nerve?
poke back of throat and the uvula will lean away from week side
Where are the cell bodies of the accessory CN?
medulla and spinal cord
What is the function of the accessory nerve?
muscles of pharynx, larynx
trapezius
SCM
Clinical implications of accessory CN?
Easily injured in surgeries
-can’t shrug or turn head
Where does the hypoglossal CN emerge from?
medulla
Where are the cell bodies of the hypoglossal CN?
medulla
What is the function of hypoglossal CN?
intrinsic and extrinsic muscles of the tongue
Clinical implications of the hypoglossal CN?
Push out tongue, it will lean towards week side
Which CNs pierce the cavernous sinus?
the ones that go to the orbit
Abducens palsy
eye being pulled medially because lateral muscle is week because of innervation problem with CN VI
What are the five motor branches of the facial CN?
temporal zygomatic buccal marginal mandibular cervical
What is the consequence of an UMN lesion of facial CN? why?
contralateral lower face weakness
-because lower face only innervate by contralateral brain
What is the consequence of a LMN lesion of facial CN?
ipsilateral whole face weakness
What is vestibular neuritis?
- affects vestibulocochlear CN
- causes sudden, severe vertigo
What is labyrinthitis?
- similar to vestibular neuritis
- but with addition of hearing symptoms (sensory type hearing loss or tinnitus
What is acoustic neuroma?
benign tumor in vestibulocochlear CN
-causes hearing and balance issues
List the different cranial nerve fibres
- SVE
- GSE
- GVE
- SSA
- SVA
- GSA
- GVA
SVE
• special visceral efferent • brachiomeric arches: o trigeminal o facial o glossopharyngeal o vagus & cranial root accessory
GSE
• general somatic efferents • voluntary motor EXCEPT for brachiometric o oculomotor o troclear o abducens o accessory o hypoglossal
GVE
• general visceral efferents
• parasympathetic (cranial part)
o oculomotor (ciliary ganglion does pupil constriction)
o facial (gland (not parotid)
o glossopharyngeal (otic ganglion -parotid gland)
o vagus (heart, resp., GIT smooth muscle)
SSA
• special somatic afferent
• vision and hearing
o optic
o vestibulocochlear
SVA
• special visceral afferent • smell and taste o olfactory o facial (ant. 2/3) o vagus (epiglotus and palate) o glossopharyngeal (post 1/3)
GSA
• general somatic afferent • general sensation o trigeminal o facial (external acoustic meatus) o glossopharyngeal (post 1/3 tongue, tonsils) o vagus (oropharynx)
GVA
• general visceral afferents
• baroreceptors and chemoreceptors
o glossopharyngeal (carotid body and sinus)
o vagus