Cranial Nerves Flashcards
Function of CN1
Special sensory
Smell - assists with taste (not important)
Course of CN1
Olfactory bulb - Olfactory tract
Pathology of CN1
URTI
Compression = Meningioma
Fracture of anterior cranial fossa - check for CSF leakage
Clinical testing for CN1
Ask for anosmia - ‘‘Have you had any recent change in your sense of smell’’
CN2 exit
Optic canal
CN2 pathology
Blindness
Reduced visual acuity
Loss of colour vision
Clinical testing of CN2
Visual fields Visual acuity - Snellen chart Colour vision - ishihara plates Pupillary reflexes - RAPD etc Fundoscopy
Function of CN3
Somatic motor & PSNS (parasympathetic nervous system?)
CN3 exit
superior orbital fissure
What muscles does CN3 supply in the eye?
Superior, Medial & Inferior rectus
What other things do CN3 supply?
Levator palpabrae superioris - damage to this results in a droopy eyelid
(as part of being PSNS) - ciliary muscles, sphincter pupillae - they will lose the ability to constrict their pupil
What causes CN3 to become damaged
Raised ICP
Aneurysm of post cerebral artery
Diabetes, MS
Clinical signs of CN3 pathology
Eyeball ‘down & out’
Ptosis
Dilated pupil
Clinical testing of CN3
H test
CN4 function
somatic motor
CN4 exit
Superior orbital fissure
What muscle does CN4 supply
Superior oblique
What causes CN4 to become damaged?
Raised ICP
Cavernous sinus
Signs of CN4 pathology
Vertical diplopia - exacerbated when looking down
Head tilt away from affected side
CN6 function
Somatic motor
CN6 exit
Superior orbital fissure
CN6 supplies what?
Lateral rectus
What causes CN6 to become damaged?
Raised ICP
CN6 pathology signs
Horizontal diplopia
Abducted eye can’t be abducted past midline
Compensatory turning of head
CN5 divisions and their exits
V1 - ophthalmic - sup orbital fissure
V2 - Maxillary - Foramen rotundum
V3 - Mandibular - Foramen ovale
What are V1 and V2 associated with
cavernous sinus
CN5 function
somatic sensory and motor
Motor = V3 only
V3 sensory supply
2/3 tongue (NOTE - not the taste, just the sensation. Taste of ant 2/3 is by CN7)
Tensor tympani
What causes CN5 to become damaged?
Trigeminal neuralgia - usually V2,3
Herpes zoster
CN5 signs of pathology
Loss of sensation
Jaw deviates towards lesion when opening mouth
Hutchinson’s sign
CN5 clinical testing
Sensation - cotton wool, pin prick etc
Motor - mastication, open mouth
Reflexes - Corneal reflex, jaw jerk
How to remember what is in the cavernous sinus?
OTOM CAT O - Oculomotor nerve (CN3) T - Trochlear nerve (CN4) O - Ophthalmic nerve (CNV1) M - Maxillary nerve (CNV2)
C A - Internal Carotid Artery
T - Junction point
CN7 Function
B for BOTH somatic and sensory
Facial muscles (motor)
Anterior 2/3 taste sensation of tongue (special sensory)
Small area around concha of auricle (sensory)
It also has a PARASYMPATHETIC supply to lots of GLANDS:
Lacrimal (parasympathetic)
Submandibular and sublingual gland (parasympathetic)
Nasal, palatine & pharyngeal mucous glands (parasympathetic)
CN7 exit
Internal acoustic meatus
CN7 nerve - explain the course of the nerve
2 roots come from the pons
Travel through internal acoustic meatus
Within the temporal bone, enter facial canal
2 roots fuse to form facial nerve
Nerve forms geniculate ganglion
Gives out greater petrosal nerve, nerve to stapedius, chorda tympani
Exits cranium via stylomastoid foramen
After exit, nerve turns superiorly and runs anterior to outer ear
Gives off posterior auricular nerve and more motor branches (belly of digastric muscle & stylohyoid muscle)
Main trunk passes through parotid and splits into 5 branches within the gland
What causes CN 7 to become damaged?
What are the clinical signs?
Reduced salivation
Loss of taste for ant. 2/3rds of tongue
Hyperacusis
Lacrimal fluid production
Any parotid gland pathology (e.g. tumours)
Herpes infection of facial nerve
Compression during forceps delivery (underdeveloped mastoid process)
Bell’s palsy
CN7 clinical testing
Facial asymmetry
Motor - raise eyebrows, purse lips, show teeth, puff out cheeks
CN8 function
Hearing (cochlear fibres)
Balance (vestibular fibres)
Course of CN8
Cochlear arises from ventral & dorsal cochlear nuclei in inferior cerebellar peduncle
Vestibular arises from vestibular nuclei complex in pons & medulla
Both combine in pons
CN8 exit
Internal acoustic meatus
CN8 pathology
2 high yield conditions:
Vestibular neuritis - inflammation of vestibular nerve
Symptoms = vertigo, nystagmus, loss of equilibrium
Labyrinthitis - inflammation of membranous labyrinth
Symptoms = hearing loss, tinnitus, vertigo, nystagmus
CN8 clinical testing
Rinne’s & Weber’s
CN9 function
Orophyranx (sensory)
Carotid body & sinus (sensory)
Posterior 1/3 tongue (sensory & special sensory/taste)
Middle ear cavity & eustachian tube (sensory)
Parotid gland (parasympathetic) **CNVII passes through but doesn’t innervate
Stylopharyngeus (motor)
Course of CN9
Originates from medulla oblongata
Exits via jugular foramen
What nerve does CN9 give rise to?
Carotid sinus nerve
Pathology signs when CN9 is damaged
loss of gag reflex
Clinical testing for CN9
Open mouth and say ahh
Inspect palate for any uvula deviation
Assess speech, cough, swallow
CN10 sensory function
Internal laryngeal n –> Laryngopharynx, Larynx
Vagus n. –> heart, GI tract
CN10 special sensory function
Taste –> root of tongue & epiglottis
CN10 motor function
Pharyngeal branch of vagus n:
Sup, mid, inf pharyngeal constrictor muscles
Palatopharyngeus
Salpingopharyngeus
Recurrent laryngeal n:
All the arytenoids, vocalis
External branch of sup laryngeal n:
Cricothyroid
Parasympathetic function of CN10
Heart & GI tract (oesophagus up to splenic flexure)
Heart - lowers HR
GI - stimulates smooth muscle contraction, secretions. (remember REST & DIGEST)
Course of CN10
Originates in medulla oblongata
Exits via jugular foramen
In neck passes into carotid sheath
R & L vagus n. travel separately at neck base level
At neck, several branches arise. One to remember is R recurrent laryngeal n.
This nerve hooks underneath R subclavian artery
Where does the L recurrent laryngeal nerve hook under?
Arch of aorta
What causes damage to CN10
Vasovagal syncope
Carotid massage
Dysphonia/aphonia (Cancer/injury)
Function of CN11
Sternocleidomastoid (motor)
Trapezius (motor)
Course of CN11
2 parts: Cranial part: Medulla oblongata Exits via jugular foramen Combines with vagus nerve
Spinal part:
Enters via foramen magnum
Exits via jugular foramen
Symptoms of pathology of CN11
muscle wasting, inability to rotate head/weakness in shrugging
CN12 function
Intrinsic & Extrinsic muscles of tongue (motor)
Course of CN12
Medulla oblongata
Exits via hypoglossal canal
Clinical testing of CN12
Check tongue for fasiculations
Stick tongue out and check for deviations