H&N9 - Cranial Nerves VII-XII

Question 1

5 features of the facial nerve (CN VII)

Origin
Route
Functions
Examinations x4
Clinical Conditions

Answer 1

1. ) Origin - pons (pontomedullary junction)
   - emerges laterally from the pontomedullary junction
2. ) Route - internal acoustic meatus –> petrous bone
   - 3 intracranial branches arise from the petrous bone
   - extracranial branches exit the base of the skull via the stylomastoid foramen
3. ) Functions - has all 4 functions:
   - special sensory, general sensory, motor, autonomic
4. ) Examination - testing muscles of facial expression (e.g. bell’s palsy) and the corneal (blink) reflex
   - corneal reflex because the facial nerve supplies the efferent limb of the reflex (afferent is ophthalmic (Va))
   - asking about other symptoms: hyperacusis (sensitive to loud noises), dry eyes and mouth, altered taste
   - examine parotid glands as extracranial branches run through it
5. ) Clinical Conditions - depends on where along the nerve route the pathology is:
   - middle ear (petrous bone), internal acoustic meatus, parotid gland (extracranial branches)

Question 2

4 functions/branches of the facial nerve

3 Intracranial Branches
Extracranial Branches

Answer 2

1. ) Greater Petrosal Nerve - autonomic (parasympathetic)
   - supplies lacrimal, nasal, and palatine glands
2. ) Chorda Tympani Nerve - special sensory (SS) and autonomic (parasympathetic)
   - SS (taste) to the anterior 2/3 of the tongue
   - autonomic to salivary glands (except parotid)
3. ) Stapedius Nerve - motor to the stapedius muscle
   - stapedius dampens down the vibration of the stapes to the inner ear, preventing damage (prevents hyperacusis)
4. ) Extracranial Branches - motor and general sensory
   - posterior auricular nerve provides motor and sensory innervation to a small area of the external ear
   - posterior belly of digastric and stylohyoid muscle
   - muscles of facial expression (branches: TZBMC)
   - it runs through parotid gland but doesn’t supply it

Question 3

4 features of the facial nerve being a mixed cranial nerve

Definition
Nerve Roots
Cell Bodies
Geniculate Ganglion

Answer 3

1.) Definition - contains sensory and motor nerve fibres, collection of different nerve types contribute axons

2. ) Nerve Roots - has 2 roots at cerebellopontine angle
   - motor root contains just motor axons
   - nervus intermedius contains sensory and autonomous (parasympa) nerve roots
3. ) Cell Bodies - cell bodies of the motor and parasympathetic nerves come from discrete area of the brainstem
   - cell bodies of the sensory nerves are found in the geniculate ganglion (outside brainstem)
4. ) Geniculate Ganglion - collection of sensory neurones of the facial nerve
   - it receives the motor, sensory, and parasympa nerve fibres and is where the branches branch off
   - any lesion past the geniculate ganglion spares the intracranial branches

Question 4

4 features of the vestibulocochlear nerve (CN VIII)

Origin
Route
1 Function
Examination

Answer 4

1. ) Origin - pons (pontomedullary junction)
2. ) Route - internal acoustic meatus –> petrous bone –> cochlea + semicircular canals
3. ) Functions - special sensory: hearing and balance
4. ) Examination - crude hearing test (whispering 99 in each ear), pure tone audiometry, asking about balance
   - Rinnes and Weber’s test

Question 5

3 clinical conditions involving the vestibulocochlear nerve

Answer 5

1. ) Hearing Loss - pathology to cochlea, cochlear component of CNVIII, or brainstem nucleus
   - presbycusis is old-age related hearing loss
2. ) Vertigo - disturbance of balance
   - pathology to semicircular canals, vestibular component of CN VIII, or brain nucleus
3. ) Acoustic Neuroma - benign tumours of Schwann cells surrounding the vestibular component of CN VIII
   - presence causes compression of the whole nerve and possibly other CNs in close proximity (facial nerve)
   - symptoms are unilateral hearing loss, tinnitus, vertigo, bell’s palsy (facial nerve affected)

Question 6

5 features of the glossopharyngeal nerve (CN IX)

Origin
Route
4 Functions
Examination 
Clinical Conditions

Answer 6

1.) Origin - medulla

2. ) Route - jugular foramen –> carotid sheath
   - leaves the carotid sheath quite early

3.) Functions - all 4 functions: SS, GS, motor, autonomic

4. ) Examination - asking patients to swallow (tested w/ vagus nerve), gag reflex test
   - taste not formally tested

5.) Clinical Conditions - isolated lesions are rare

Question 7

4 functions of the glossopharyngeal nerve

Answer 7

1.) Special Sensory - taste of posterior 1/3 of tongue

2. ) General Sensory - posterior 1/3 of tongue,
   - tonsils and oropharynx (mouth)
   - middle ear and tympanic membrane (ear)
   - carotid body and carotid sinus (carotid)
3. ) Motor - one pharynx muscle (stylopharyngeus) which assists in swallowing
4. ) Autonomic - parasympathetic to parotid gland

Question 8

5 features of the vagus nerve (CN X)

Origin
Route
3 Functions
Examination
Clinical Conditions

Answer 8

1.) Origin - medulla

2. ) Route - jugular foramen –> carotid sheath
   - goes through neck, into thorax and abdomen
   - R recurrent laryngeal nerve turns under R subclavian
   - L recurrent laryngeal nerve turns under aortic arch

3.) Functions - general sensory, motor, autonomic

4. ) Examination - note patient’s speech, cough, and ability to swallow, gag reflex (efferent limb)
   - note movement of uvula and soft palate when saying ‘Aaah’ (if normal, it rises on both sides)
5. ) Clinical Conditions - isolated lesions are rare
   - injury to recurrent laryngeal nerve following thyroid surgery can cause hoarseness and dysphonia (difficulty speaking)

Question 9

3 functions of the vagus nerve

Answer 9

1. ) General Sensory
   - lower pharynx and whole larynx
   - small part of external ear and tympanic membrane

2.) Motor - muscles of pharynx, larynx, and soft palate

3. ) Autonomic - parasympathetic
   - mucosal glands in the pharynx/larynx,
   - smooth muscle of the oesophagus and trachea,
   - smooth muscle and mucosal glands within the rest of the respiratory and GI tract
   - heart

Question 10

4 features of the accessory nerve (CN XI)

Origin
Route
1 Function
Examinations

Answer 10

1. ) Origin - medulla
   - also has rootlets from the cervical spine
2. ) Route - jugular foramen –> carotid sheath
   - passes deep to SCM and trapezius

3.) Function - motor to SCM and trapezius

4. ) Examinations
   - shrug shoulder against resistance (trapezius)
   - turn head against resistance (SCM)

Question 11

5 features of the hypoglossal nerve (CN XII)

Origin
Route
1 Function
Examination
Clinical Conditions

Answer 11

1.) Origin - medulla

2. ) Route - exits skull via hypoglossal canal
   - runs medial to angle of mandible and crosses ICA and ECA in the neck
3. ) Function - motor to all the muscles of the tongue (except one)
4. ) Examination - inspection and movement of tongue
5. ) Clinical Conditions - rare, damage causes weakness and atrophy of the tongue on ipsilateral side