12. CNVII - Facial Nerve

Question 1

What information does the chordae tympani carry? Which nuclei are involved?

Answer 1

Afferent special sensory: taste anterior 2/3 of tongue (superior salivatory nucleus)
Visceral motor: submandibular and sublingual glands (ptergopalatine nucleus)

Question 2

What are the components of the facial nerve?

Answer 2

Facial nerve has 4 components:

1. Branchial motor: Muscles of facial expression, stylohyoid, posterior belly of digastric, platysma, stapedius, buccinator (facial motor nucleus of VII; nerves are TZBMCP: temporal, zygomatic, buccal, mandibular, cervical, posterior auricular n.)
2. Visceral motor: Ptergopalatine n for submandibular and sublingual glands; greater petrosal n for lacrimal glands
3. Special sensory: taste anterior 2/3 (chorda tympani)
4. Somatic sensory: auricle, skin behind ear, concha, external auditory meatus, outer surface of tympanic membrane (posterior auricular branch)

Question 3

Order of branching of nerves off of facial nerve.

Answer 3

1. greater petrosal nerve
2. n. to stapedius
3. chorda tympani
4. posterior auricular
   5, 6, 7, 8, 9. Temporal, zygomatic, buccal, mandibular, cervical

Question 4

Central nerves vs peripheral nerves

Answer 4

Central nerves carry bilateral innervation to facial m. above eyes
Peripheral nerves carry innervation to the ipsilateral whole side of face

Question 5

What is the stapedial reflex?

Answer 5

involuntary m. contraction in response to a high intensity sound stimulus –> dampens loud noises to protect tympanic membrane and ear structures

Question 6

Neuropraxia

Answer 6

Transient episode of nerve damage; no myelin sheath or nerve damage

Question 7

Axonotmesis. Can lead to what?

Answer 7

Damage to the axon but not myelin sheath

Dyskinesia possible if axon regenerates and forms inappropriate connection with adjacent nerve

Question 8

Neurotmesis

Answer 8

Nerve and nerve sheath damage

Question 9

Wallerian degeneration

Answer 9

Nerve is cut or damaged; axon distal to it degenerates

Regrowth occurs if neurolemma is intact

Question 10

Schirmer Tear Test

Answer 10

Filter paper to lower lids compare tear production over fixed amount of time; greater petrosal n.

Question 11

Stapedial acoustic reflex test tests for which nerve

Answer 11

nerve to stapedius

Question 12

Salivary flow test

Answer 12

Collect saliva formed from Wharton’s (submandibular) duct to asses saliva production over fixed time

Question 13

Electrogustometry

Answer 13

Measure amount of electricity needed to stimulate tongue sensation; compare sides

Question 14

Corneal reflex

Answer 14

Touch cornea, CN7 should cause eye to blink

Question 15

Threat reflex

Answer 15

Go in for punch, but stop prior to face. They should blink

Question 16

Tx for bell’s palsy

Answer 16

Steroids, optional acyclovir

Question 17

Tx for Otitis

Answer 17

Myringotomy (drain middle ear), mastoidectomy, nerve decompression

Question 18

Which nerve keeps the eye open?

Answer 18

CN3

Question 19

Which nerve closes the eye?

Answer 19

CN7