4) Cranial Nerves Flashcards
Name the 12 cranial nerves
I - Olfactory II - Optic III - Oculomotor IV - Trochlear V - Trigeminal VI - Abducens VII - Facial VIII - Vestibulocochlear IX - Glossopharnygeal X - Vagus XI - Spinal Accessory XII - Hypoglossal
Give the broad functions of each of the 12 CNs
Some Say…
I Some - Sensory II Say Sensory III Marry - Motor IV Money - Motor V But - Both VI My - Motor VII Brother - Both VIII Says - Sensory IX Big - Both X Boobs - Both XI Matter - Motor XII Most - Motor
Where does CN I exit the cranium?
Foramina in cribriform plate of ethmoid bone to reach nose
What are the main actions of the Olfactory nerve?
Special sensory fibres:
uppermost part of nasal cavity
SMELL
What is rhinorrhea?
Leakage of CSF from the nose
Associated with fractures of cribriform plate
Where does CN II exit the cranium?
Optic canal
What are the main actions of the Optic nerve?
Special sensory fibres:
VISION
What is anosmia?
Loss of smell
Associated with fractures of cribriform plate
Name some common nerve lesions of CN II
Loss of pupillary constriction & Visual field defects Due to: Direct trauma to eye or orbit Fracture of optic canal Pressure on optic pathway
Where does CN III exit the cranium?
Superior orbital fissure
What are the main somatic motor actions of the Oculomotor nerve?
Innervate: Superior, inferior, & medial rectus
Inferior oblique
LPS
(raise superior eyelid, turns eyeball sup, inf, & med.)
What are the main visceral motor actions of the Oculomotor nerve?
Parasympathetic innervation:
Sphincter of pupil & ciliary muscle
(constricts pupil & accomodates lens of eye)
Which nerve will be affected during a fracture or aneurysm involving the cavernous sinus?
Oculomotor CN III
Dilated pupil, ptosis
Eye turns DOWN & OUT
Pupillary reflex on side of lesion lost
Where does CN IV exit the cranium?
Superior orbital fissure
What are the main actions of the Trochlear nerve?
Motor:
Innervates Superior Oblique
What nerve lesions may occur to the Trochlear nerve?
Stretching of nerve during its course around brainstem
Orbit fractures
Inability to look down when eye is adducted
Name the 3 divisions of the Trigeminal nerve
Ophthalmic (Vi)
Maxillary (Vii)
Mandibular (Viii)
Where does the Ophthalmic nerve (Vi) leave the cranium?
Superior orbital fissure
Where does the Maxillary nerve (Vii) leave the cranium?
Foramen rotundum
Where does the Mandibular (Viii) leave the cranium?
Foramen ovale
What are the main actions of the Ophthalmic nerve?
Sensory:
cornea, skin of forehead, scalp, eyelids, nose & mucosa of nasal cavity & paranasal sinuses
What are the main actions of the Maxillary nerve?
Sensory:
Skin of face over maxilla incl. upper lip, maxillary teeth, mucosa of nose, maxillary sinuses & palate
What are the main actions of the Mandibular nerve?
Sensory:
skin, side of head over mandible incl. lower lip, mandibular teeth, TMJ, mucosa of mouth and ant. 2/3 of tongue
Motor:
muscles of mastication, mylohyoid, ant. belly of digastric, tensor veli palatini, tensor tympani
What will lesions of the Trigeminal nerve lead to?
Paralysis of muscles (mastication)
Sharp, intense facial pain
Where does CN VI exit the cranium?
Superior orbital fissure
Which nerves exit the cranium via the superior orbital fissure?
Oculomotor (III)
Trochlear (IV)
Ophthalmic (Vi)
Abducent (VI)
What are the main actions of the Abducent nerve?
Motor:
Lateral Rectus
(turns eye laterally)
How might the abducens nerve be lesioned?
Fractures involving cavernous sinus or orbit
Eye fails to move laterally
Diplopia on lateral gaze
Where does CN VII exit the cranium?
Internal acoustic meatus;
Facial canal;
Stylomastoid foramen
What are the main actions of the Facial nerve?
Special Sensory: Taste, ant. 2/3 tongue & palate Motor: Muscles of facial expression Scalp, stapedius, stylohyoid & post. belly of digastric Visceral Motor: Parasympathetic innervation to submandibular & sublingual salivary gland (chorda tympani) lacrimal gland & glands of nose & palate
What may be the consequences of a laceration or contusion in the Parotid region?
CN VII
Paralysis of facial muscles
Eye remains open, angle of mouth droops, forehead doesn’t wrinkle
Bell’s palsy
What might happen to someone who fractures their temporal bone?
Bell’s palsy
Involvement of cochlear nerve & chorda tympani
Dry cornea, loss of taste ant. 2/3 of tongue
What effects will an intracranial haematoma have on CN VII?
Forehead wrinkles because of bilateral innervation of frontalis muscle
Paralysis of contralateral facial muscles
Where does CN VIII exit the cranium?
Internal acoustic meatus
What are the main actions of the Vestibulocochlear nerve?
Vestibular: Controls BALANCE
Cochlear: HEARING
What may lesions of CN VIII cause?
Progressive, unilateral hearing loss, tinnitus, vertigo
Caused by: tumour of nerve (acoustic neuroma), skull fractures, ear infections
Acoustic neuroma frequently impairs CN VII too
Where does CN IX exit the cranium?
Jugular foramen
What are the main actions of the Glossopharyngeal nerve?
Special sensory: Taste to post. 1/3 tongue
Visceral sensory: Parotid gland, carotid body & sinus, pharynx & middle ear
General sensory: Cutaneous external ear
Motor:
Stylopharyngeus
Parasymp. to parotid gland
What nerve lesions may occur to CN IX?
Glossopharyngeal
Deep lacerations of neck
Loss of taste to post. 1/3 tongue
Where does CN X exit the cranium?
Jugular foramen
What are the main sensory actions of the Vagus nerve?
Visceral sensory: Lower pharynx & larynx, trachea, oesophagus, bronchi, heart, stomach, intestine
General sensory: External auditory meatus, back of auricle
Special sensory: Taste from epiglottis & palate
What are the main motor actions of the Vagus nerve?
Innervates all muscles of pharynx except stylopharyngeus
All muscles of airways, larynx, heart, GI tract
All palate muscles except tensor veli palantini
(parasymp. to trachea, bronchi, digestive tract, cardiac muscle)
How might hoarseness of the voice occur?
Damage to Recurrent laryngeal branch of Vagus
carcinoma, enlarged lymph node, aneurysm
How will a brainstem lesion or deep laceration of the neck affect CN X?
Sagging of soft palate
Deviation of uvula to normal side
Hoarseness - paralysis of vocal cord
How might the superior laryngeal nerve be damaged?
Thyroidectomy
External branch lies close to sup. thyroid artery
Damaged when ligating blood vessel
Where does CN XI exit the cranium?
Jugular foramen
What are the main actions of the Spinal accessory nerve?
Motor:
Spinal - SCM & Trapezius
Cranial - Innervates pharynx, larynx & soft palate
How will nerve lesions caused by surgery or laceration to CN XI present?
Paralysis of SCM & superior fibres of Trapezius
Should droop
Where does CN XII exit the cranium?
Hypoglossal canal
What are the main actions of the Hypoglossal nerve?
Motor:
Innervates all extrinsic & intrinsic muscles of tongue except palatoglossus
How would a nerve lesion of CN XII be caused and how would it present?
Neck laceration or basal skull fracture
Protruded tongue deviates towards affected side
(due to arrangement of muscles)
