Cranial Nerves Flashcards
Cranial nerve 1 origin
Olfactory
Cerebrum
CN 1 exit skull
Cribriform plate
CN 1 modality /components
Special visceral Sensory (senses derived from endoderm)
Smell
CN II origin
Cerebrum
CN II exit skull
Optic canal
CN 2 modalities/components
Special somatic sensory (senses derived from ectoderm)
Sight
CN 3 origin
Midbrain - pontine junction
CN 3 components/modality
Motor
General somatic motor: 4 extrinsic eye muscles and levator palpebrae superioris
General visceral motor: parasympathetic to pupillary sphincter and ciliary m
CN 3 exit skull
Superior orbital fissure
CN 4 origin
Midbrain posterior (longest intracranial length of all CNs)
CN4 exit skull
Superior orbital fissure
CN4 modality/components
Motor
General somatic motor: superior oblique
CN V origin
Pons
CN 5.1 exit skull
Superior orbital fissure
Ophthalmic nerve modality/components
General somatic sensory (skin): scalp, forehead, nose
CN 5.2 exit skull
foramen rotundum
Maxillary nerve modality/ components
General somatic sensory: cheeks, lower eye lid, nasal mucosa, upper lip, upper teeth, palate
CN 5.3 exit skull
Foramen ovale
Mandibular nerve modality/ components
General somatic sensory: anterior 2/3 tongue, skin over mandible, lower teeth
Special visceral motor (mm derived from pharyngeal arches) :muscles of mastication, tensor tympani muscle
CN 6 origin
Pontine - medulla junction
CN 6 exit skull
Superior orbital fissure
CN6 modality/components
General somatic motor: lateral Rectus
CN 7 origin
Pontine-medulla junction
CN 7 exit skull
Internal acoustic meatus
Stylomastoid foramen
CN 7 modality/components
Motor and sensory
General somatic sensory: external ear . stapedius mm
Special visceral sensory: taste ant 2/3 tongue, hard and soft palate
Special visceral motor: muscles facial expression
General visceral motor: parasympa- lacrimal, submandibular, sublingual, mucous glands of mouth and nose.
CN 8 origin
Pontine- medullary junction
CN8 exit skull
Internal acoustic meatus
CN8 modality/components
Special somatic sensory: hearing and balance
CN IX origin
Medulla oblongata posterior to olive
CN IX exit skull
Jugular foremen
CN IX modality/components
Motor and sensory
General somatic sensory: posterior 1/3 tongue, external ear, middle ear cavity
General visceral sensory: carotid body and sinus
Special visceral Sensory: taste post 1/3 tongue
General visceral motor: parotid gland parasympa
Special visceral motor: stylopharyngeus
CN X origin
Medulla oblongata posterior to the olive
CN X exit skull
Jugular foramen
CN X modality/components
Motor and sensory (vagus)
General somatic sensory: external ear, larynx, pharynx
General visceral sensory: larynx, pharynx, thoracic and abdominal viscera
Special visceral sensory: taste from epiglottis region of tongue
General visceral motor: parasympa. smooth muscles pharynx, larynx, most of GIT. Palatoglossus
Special visceral motor: most muscles pharynx and larynx
CNXI origin
Medulla oblongata posterior to olive
CN XI exit skull
Jugular foramen
CN XI modality/components
Motor
General somatic motor: trapezius, sternocleidomastoid
Special visceral motor: a few fibres run with CNX to viscera
CNXII origin
Medulla oblongata anterior to olive
CNXII exit skull
Hypoglossal canal
CN XII modality/components
General somatic motor: intrinsic and extrinsic muscles of tongue, except palatoglossus (CNX)
How test olfactory nerve
Ask if any changes in smell
How test optic nerve (8)
- Pupil size, symmetry and shape
- visual acuity with Snellen chart!
- direct and consensual pupillary reflex!
- swinging light test to check for relative afferent pupillary defect (Marcus Gunn pupil) (positive = paradoxical dilatation of affected pupil when light shone into it)
- Accommodation reflex: pupillary convergence and constriction when focus from far object to finger!
- colour vision using Ishihara plates at arms length
- visual fields: pt cover one eye and you mirror patient. Your finger equal distance between you and patient. Bring closer to test peripheral visual field! Ask if can see your face to check for central scotoma . Then how many hands do they see to test for hemisnopia eg. Then how many fingers in each visual field. Then how many fingers total for visual neglect. Then tell me when you can see my finger for periph field.
Do opposite to test blind spot - fundoscopy!
Describe the muscles responsible for the eye movements (6)
Up: superior rectus and inferior oblique
Down: inferior rectus, superior oblique
Adduction: medial rectus (and secondary action of superior rectus, inferior rectus)
Abduction: lateral rectus, superior oblique, inferior oblique
Medial rotation: superior oblique (superior rectus)
Lateral rotation: inferior oblique (inferior rectus )
Function superior rectus?
Primary: elevation
Secondary: adduction, medial rotation
Function inferior rectus?
Primary: depression
Secondary: adduction, lateral rotation
Function medial rectus?
Adduction
Function lateral rectus?
Abduction
Function superior oblique?
- depress
- abduct
- medial rotation
Function inferior oblique?
- Elevate
- Abduct
- laterally rotate
How test trigeminal nerve (6)
Sensory
- light touch and pinprick of forehead (ophthalmic division v1 ) , cheek (maxillary v2 ), lower jaw (mandibular V3)
Motor: muscles of mastication
- masseter muscle (clench teeth)
- temporalis muscle
- lateral and medial plerygoid muscles (open and close jaw against resistance )
Reflexes
- jaw jerk reflex
- corneal reflex
- nasal tickle
How test facial nerve (10)
Sensory
- ask if taste changes (anterior 2/3 of tongue)
Motor
- ask if hearing changes (stapedius muscle. Paralysis = hyperacusis )
- frontalis muscle: raise eyebrows
- orbicularis oculi: scrunched eyes
- buccinator: blow out cheeks
- levator anguli oris and zygomaticus major: smile
- buccinator and orbicularis oris: pursed lips (whistle)
- platysma
Autonomic
- lactimation
- salivation
How test vestibulocochlear nerve (5)
Sensory only
- ask if change in hearing
- whisper word from 60 cm away
- Rinne and Weber’s test
- turning test: patient march on spot with arms out and eyes closed. If vestibular lesion, will turn towards side of lesion
- Vestibular-ocular reflex: patient fixate on your nose throughout. Use your hands to rapidly rotate their head each way. Should maintain ocular fixation.
How test glossopharyngeal nerve (3)
Motor
- stylopharyngeus muscle: elevates pharynx during swallow and speech
(Afferent limb of swallow)
Sensory
- taste post 1/3 tongue
Reflex
- afferent limb of gag reflex
How test vagus nerve (5)
Motor
- speech
- say “ahh” and inspect soft palate and uvula. Lesion = deviate to normal side
- cough: lesion = weak, non-explosive bovine cough
- swallow: efferent limb
Reflex
- efferent limb of gag reflex
How test accessory nerve (2)
Motor
- sternocleidomastoid: palpate both heads
- trapezius
How test hypoglossal nerve (3)
Motor to extrinsic muscles of tongue except palatoglossus (vagus)
- fasciculation’s and wasting while tongue in mouth
- protrude: deviation (will deviate to side of lesion)
- push pt tongue against cheek
- speed of tongue movement
How does CN iii palsy present
- Down and out (unopposed action of lateral rectus and superior oblique)
- Ptosis (levator palpebrae superioris)
- mydriasis (loss of parasympathetic fibres to sphincter pupillae muscle)
(With: surgical 3rd nerve palsy, without: medical 3rd nerve palsy )
How does CN iv palsy present
- Vertical diplopia, often compensated for by tilting head forward and tucking chin in
- Torsional diplopia compensated by tilting head to other side
How does CN vi palsy present
Convergent squint and horizontal diplopia
Define exotropia
Eye at rest: laterally
Cover test direction of shift: medially
Define esotropia
Eye at rest: medial
Cover test direction of shift: laterally
Define hypertropia
Eye at rest: up
Cover test direction of shift: down
Define hypotropia
Eye at rest: Down
Cover test direction of shift: up
How does facial nerve palsy caused by lower motor neuron present and example
- Weakness of all ipsilateral muscles of facial expression
- Bell’s palsy
How does facial nerve palsy caused by upper motor neuron lesion present and example
- Unilateral facial weakness with sparing of upper facial muscles ( frontalis)
- stroke
Name features Bell’s palsy (5)
= CN VII LMN palsy
- Weakness of all ipsilateral muscles of facial expression
- decreased/ absent lacrimation
- hyperacuses
- Loss taste anterior 2/3 tongue
- Vesicles external ear canal and lobe due to herpes zoster infection
Name the near triad of accommodation
- Convergence
- miosis
- accommodation of lens
Name the afferent and efferent limbs of the corneal reflex
Afferent: cn V
Efferent: cn vii (orbicularis oculi)
Define bulbar palsy
Impaired function of cranial nerves 9, 10,11 and 12.
All originate in medulla oblongATA
Describe innervation of the tongue
Sensory
- anterior 2/3: trigeminal Nerve (mandibular division, lingual nerve)
- posterior 1/3 : glossopharyngeal Nerve
Taste
- anterior 2/3: facial nerve (chorda tympani)
- posterior 1/3 : glossopharyngeal Nerve
Name 6 causes LMN CN VII lesions
- vascular: cerebrovascular ischaemia
- idiopathic: Bell’s palsy (pregnancy, DM)
- nerve; posterior fossa tumours
- infective: herpes zoster (Ramsay Hunt syndrome), EBV, CMV, HIV
- inflammatory: sarcoidosis
- autoimmune: rheumatoid arthritis
Name 4 causes umn CN VII lesions
- Cerebrovascular incident
- intracranial tumour
- multiple sclerosis
- HIV