Cranial Nerves V & VII

Question 1

trigeminal nerve

Answer 1

cranial nerve 5
composed of 3 branches:
1. ophthalmic branch
2. maxillary branch
3. mandibular branch

Question 2

function of the ophthalmic branch

Answer 2

sensory to the face

Question 3

function of the maxillary branch

Answer 3

sensory to the face

Question 4

function of the mandibular branch

Answer 4

sensory to the face
motor to muscles of mastication

Question 5

where does the mandibular branch exit the skull

Answer 5

oval foramen

Question 6

trigeminal ganglion

Answer 6

contains sensory cell bodies

axons enter the brainstem to synapse in the pons

Question 7

autonomous zones

Answer 7

regions of the face that are only innervated by 1 branch of CN V

when testing CNs - need to test in autonomous zones

Question 8

motor nucleus

Answer 8

located in the pons (brainstem)

axons exit the brainstem –> trigeminal canal in the petrous temporal bone

Question 9

what are the steps of a cranial nerve exam

Answer 9

menace response
PLRs
trigeminal-facial reflexes
- corneal reflex
- palpebral reflex
- vibrissae
- lip pinch
- nasal stimulation
physiologic nystagmus
facial symmetry
gag reflex

Question 10

menace response A&E

Answer 10

A: CN II (optic)
E: CN VII (facial)

Question 11

pupillary light reflex A&E

Answer 11

A: CN II (optic)
E: CN III (oculomotor)

Question 12

corneal reflex A&E

Answer 12

A: CN V (trigeminal - ophthalmic)
E: CN VI & CN VII (abducens & facial)

Question 13

palpebral reflex A&E

Answer 13

A: CN V (trigeminal - ophthalmic and maxillary)
E: CN VII (facial)

Question 14

vibrissae response A&E

Answer 14

A: CN V (trigeminal - maxillary)
E: CN VII (facial)

Question 15

lip pinch response A&E

Answer 15

A: CN V (trigeminal - maxillary and mandibular)
E: CN VII (facial)

Question 16

nasal stimulation response A&E

Answer 16

A: CN V (trigeminal - maxillary)
E: CN VII (facial)

Question 17

physiologic nystagmus A&E

Answer 17

A: CN VIII (vestibulocochlear)
E: CN III, IV, VI (oculomotor, trochlear, abducens)

Question 18

facial symmetry

Answer 18

temporalis + masseter symmetry - CN V (trigeminal - mandibular)

drooping lips/ear carriage - CN VII (facial)

drop jaw, difficulty closing mouth, inability to prehend food - CN V (trigeminal - mandibular)

Question 19

gag reflex A&E

Answer 19

A: CN IX, X (glossopharyngeal, vagus)
E: CN IX, X, XII (glossopharyngeal, vagus, hypoglossal)

Question 20

clinical signs of CN V dysfunction

Answer 20

1. decreased or abnormal sensation
2. decreased or absent CN reflexes
3. masticatory muscle paresis/paralysis
4. masticatory muscle atrophy
5. +/- trismus (difficulty opening jaw)

Question 21

clinical signs of CN VII dysfunction

Answer 21

1. motor: inability to close eye, drooping ear/eyelid/lip, widening of palpebral fissure, lack of nostril flare, abnormal facial reflexes
2. sensory: impaired taste, reduced/absent sensation on medial pinna
3. autonomic: dry eye/nose

Question 22

central CN V signs

Answer 22

brainstem lesion

1. motor and sensory dysfunction
2. brainstem signs
   - CNVII and VIII deficits
   - ipsilateral hemiparesis
   - obtunded mentation
   - CP deficits
   - cerebellar signs
   - long tract signs (CP and paresis)

Question 23

peripheral CN V signs

Answer 23

peripheral nerve lesion

1. signs depend on location of the lesion (branch specific signs)
2. NO brainstem signs

Question 24

what are DDX for lesions localized to central or peripheral CN V

Answer 24

1. idiopathic trigeminal neuropathy
2. masticatory muscle myositis (MMM)
3. neoplasia
4. infection
5. trauma

Question 25

idiopathic trigeminal neuropathy

Answer 25

“trigeminal neuritis”

PERIPHERAL lesion

acute onset dropped jaw and inability to close mouth

Question 26

idiopathic trigeminal neuropathy clinical signs

Answer 26

dysphagia
drooling
unilateral or bilateral atrophy
+/- Horner’s
+/- facial paralysis

Question 27

how to diagnose idiopathic trigeminal neuropathy

Answer 27

diagnosis of exlusion - rule out other causes of CN V deficits

Question 28

idiopathic trigeminal neuropathy treatment

Answer 28

supportive care

resolves in 2-6 weeks

Question 29

masticatory muscle myositis (MMM)

Answer 29

bilateral muscle swelling and pain with NO dropped jaw

usually has trismus

Question 30

facial nerve functions

Answer 30

cranial nerve 7

1. motor: muscles of facial expression
2. sensory: inner pinna
3. taste: rostral 2/3 of tongue
4. parasympathetic: lacrimal and salivary glands

Question 31

where do the motor fibers of CN VII originate from

Answer 31

motor nucleus of CN VII in the brainstem

very closely associated with CNVIII

Question 31

how to test autonomic function of CN VII

Answer 31

schirmer tear test (lacrimation)

Question 32

central CN VII signs

Answer 32

brainstem lesion

1. motor, sensory, and autonomic dyfunction
2. ipsilateral CNVII paresis/paralysis
3. dry eye
4. brainstem signs

Question 33

peripheral CN VII signs

Answer 33

intraosseous nerve lesion

1. CN VII paresis/paralysis
2. NO brainstem signs
3. may have middle ear signs or Horner’s syndrome

Question 34

what are DDX for lesions localized to central or peripheral CN VII

Answer 34

1. idiopathic facial nerve paralysis
2. infection
3. neoplasia
4. trauma
5. metabolic
6. inflammation
7. motor unit disease

Question 37

how does infection cause CN VII deficits

Answer 37

extension of otitis media or interna causing inflammation –> compression of CN VII