Facial Nerve

Question 1

facial nerve enters the temporal bone through the _______

Answer 1

facial nerve enters the temporal bone through the internal auditory meatus

Question 2

the facial nerve passes across the top of the inner ear to reach the ________, which contains cell bodies of general sensory and special sensory (taste) neurons of the facial nerve

Answer 2

the facial nerve passes across the top of the inner ear to reach the geniculate ganglion, which contains cell bodies of general sensory and special sensory (taste) neurons of the facial nerve

ganglion contains only pseudounipolar sensory cell bodies, no synapses - motor fibers of CN VII pass through the ganglion

Question 3

the facial nerve gives rise to the _______, which contains preganglionic parasympathetic fibers destined for the pterygopalatine ganglion and special sensory taste fibers destined for the palate

Answer 3

the facial nerve gives rise to the greater petrosal nerve, which contains preganglionic parasympathetic fibers destined for the pterygopalatine ganglion and special sensory taste fibers destined for the palate

Question 4

what is contained in the chorda tympani?

Answer 4

innervated by facial nerve (CN VII), contains special sensory taste fibers (anterior 2/3 of tongue) and preganglionic parasympathetic fibers both destined for submandibular ganglion (via lingual nerve, branch of CN V3)

Question 5

the chorda tympani is innervated by facial nerve (CN VII) and contains special sensory taste fibers (anterior 2/3 of tongue) and preganglionic parasympathetic fibers destined for submandibular ganglion via _______

Answer 5

innervated by facial nerve (CN VII), contains special sensory taste fibers (anterior 2/3 of tongue) and preganglionic parasympathetic fibers destined for submandibular ganglion via lingual nerve

*note the lingual nerve is a branch of CN V3, and is only here a pathway to carry the CN VII sensory taste and parasympathetic fibers both headed to submandibular ganglion

Question 6

facial nerve leaves the temporal bone by exiting through the ______ foramen

Answer 6

facial nerve leaves the temporal bone by exiting through the stylomastoid foramen - between the styloid and mastoid processes

Question 7

what clinical finding of a facial nerve lesion will only only occur if the lesion is proximal to the geniculate ganglion?

Answer 7

reduced lacrimation

other clinical findings:
- loss of facial muscle function
- sensory abnormality behind ear
- reduction of saliva
- reduction of taste
- hyperacusis

Question 8

what clinical finding of a facial nerve lesion will only occur if the lesion is before the facial nerve reaches the stapedius?

Answer 8

hyperacusis - recall CN VII innervates stapedius

other clinical findings:
- loss of facial muscle function
- sensory abnormality behind ear
- reduction of saliva
- reduction of taste

[if proximal to geniculate ganglion, lacrimation is reduced, as well]

Question 9

what clinical finding of a facial nerve lesion will only occur if the lesion is before CN VII reaches the chorda tympani?

Answer 9

reduction of taste/ saliva - recall chorda tympani contains special sensory taste cell fibers for anterior 2/3 of tongue, CN VII also innervates salivary glands

other clinical findings:
- loss of facial muscle function
- sensory abnormality behind ear

[if proximal to stapedius - hyperacusis, and if proximal to geniculate ganglion - hyperacusis + reduced lacrimation]

Question 10

what clinical finding of a facial nerve lesion will only occur if the lesion is before CN VII reaches the stylomastoid foramen?

Answer 10

sensory abnormality behind ear

will also present with loss of facial muscle function

[if proximal to chorda tympani - reduced taste/saliva, if proximal to stapedius - add hyperacusis, if proximal to geniculate ganglion - add reduced lacrimation]

Question 11

if the facial nerve is lesioned within the parotid gland, what is the only presenting symptom?

Answer 11

loss of facial muscle function

basically, this is the end of the line, and all other clinical findings are proximal to this point (reduced saliva/taste, hyepracusis, reduced lacrimation, sensory abnormality behind ear)

Question 12

which of the following lesion location for CN VII (facial) will present with the most and fewest clinical findings, respectively?
a. proximal to geniculate ganglion
b. between geniculate ganglion and stapedius
c. between stapedius and chorda tympani
d. between chorda tympani and stylomastoid foramen
e. within parotid gland

Answer 12

within parotid gland = LEAST, loss of facial muscle function only

between chorda tympani and stylomastoid foramen - add sensory loss behind ear

between stapedius and chorda tympani - add reduced salivation/taste

between geniculate ganglion and stapedius - add hyperacusis

proximal to geniculate ganglion = MOST, add reduced lacrimation