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ENT Secrets > Chapter 42 - Facial nerve > Flashcards

Chapter 42 - Facial nerve Flashcards

1
Q

Functions of CN VII other than motor

A

PNS to lacrimal, submandibular, sublingual glands, minor salivary/mucosal glands nose and palate
Taste to tongue ant 2/3, palate, tonsillar fossa
sensation from EAC, concha
sensation nasal mucosa, palate, pharynx
SNS to middle meningeal artery

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2
Q

When facial nerve paralysis is likely a neoplasm not Bell’s palsy

A 
slow, progressive onset
No improvement in 3 mo
facial twitching
recurrent episodes
other CN involvement, hearing loss
palpable mass in parotid or visible in middle ear
Adult, unilateral middle ear effusion
skin lesions suggesting skin cancer
prolonged ear pain
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3
Q

How to treat Bell’s palsy

A

PO steroids within 72 hr onset
May use antivirals in combination with steroids
Eye care

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4
Q

Do you need imaging for Bell’s Palsy?

A

Not if PE/Hx consistent with it

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5
Q

What besides CN VII can close the upper eyelid?

A

Passive closure occurs by relaxation of levator palpebrae (CN III)

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6
Q

Where is VII most prone to entrapment with swelling?

A

labyrinthine segment - narrowest portion of fallopian canal

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7
Q

Geniculate ganglion, nerve exiting from here

A

junction of lab and tymp portions of VII
Special sensory cells – taste
Greater superficial petrosal nerve (first br of CN VII) with PNS to lacrimal gland branches off at anterior margin of this ganglion

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8
Q

Single most important factor in chances that CII will regenerate

A

If nerve slowly lost function over days or if it lost it immediately at time of trauma

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9
Q

Muscles innervated by VII

A

facial expression, platysma, stapedius, stylohyoid, digastric posterior belly

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10
Q

Anatomic segments of fallopian canal with length

A

Labyrinthine: IAC to gen ganglion. 3-5mm
Tympanic: GG to pyramidal process. 8-11mm. Begins at second genu (1st genu intrapontine). Bony dehiscence here.
Mastoid: pyramidal process to SMF, 10-14mm

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11
Q

Most common site of iatrogenic injury of CN VII during ear surgery

A

Tympanic segment

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12
Q

3 main segments of facial nerve, and their length

A

Intracranial (pons, CPA, IAC) 23-34mm
Intratemporal (fallopian canal) 20-30mm
Extratemporal (from SMF) 15-20mm

IAC itself is 8-10mm long

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13
Q

Nervus intermedius

A

division carrying non-motor segments
fuses with CN VII in IAC
chorda is terminal extension

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14
Q

Chorda tympani

A

PNS to submandibular, sublingual, and taste ant 2/3 tongue
Exits tympanic cavity via petrotympanic fissure
Joins lingual branch of trigeminal nerve

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15
Q

Muscles innervated by temporal br

A

frontalis, corrugator supercilii, procedrus, upper orb

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16
Q

Zygomatic innervates:

A

lower orb oculi

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17
Q

Buccal innervates:

A

zygomaticus major and minor, levator anguli oris, buccinator, upper orb oris

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18
Q

Marginal Mand innervates:

A

lower orb oris, depressor anguli oris, depressor labii inferiorlis, mentalis

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19
Q

Cervical innervates:

A

platysma

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20
Q

Facial nerve landmarks

A

Tragal pointer (triangular extension of tragus), 1cm inferior/deep
Follow posterior belly to styloid…SMF is deep, SMF 25mm deep to skin surface (in children nerve much closer to skin as mastoid underdeveloped)
6-8mm deep to end of Tympanomastoid fissure
Follow peripheral branch back

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21
Q

Neuropraxia

A

lesion stops axplasm flow.
Swelling, drug blockade
Nerve viable, returns to NL when block corrected
Electrophysiologic testing is NL
EMG doesn’t show voluntary motor action because potential don’t cross blockade

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22
Q

Axonotmesis

A

Wallerian degeneration distal to lesion
Oreservation of motor axon endoneural sheaths
Mild crush/stretch
Nerve shows rapid and complete degen, loss of voluntary motor units
Regeneration to motor end plate will occur if endoneural tubules intact

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23
Q

Neurotmesis

A

Wallerian degeneration plus endoneural tubule loss
Complete nerve degen
Regeneration dependent on endoneurium integrity, perineurium and epineurium integrity, extent of ischemia/scarring

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24
Q

Synkinesis

A

Wallerian degen –> axon regeneration –> cross wiring in which voluntary movement of one muscle induces involuntary movement of another
Facial trunk repairs usually have this

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25
Q

HB II

A 
Mild dysfunction
Slight weakness close inspection, normal symmetry/tone
Slight asymmetry mouth
Complete closure eye minimal effort
Moderate to good forehead
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26
Q

HB III

A 
Obvious, not disfiguring asymmetry
Normal symmetry/tone
Mouth: slight weak maximum effort
Eye: complete closure with effort
Forehead: slight to moderate
27
Q

HB IV

A

Moderately Severe. Obvious weakness, possible dysfunction
Mouth: asymmetric maximum effort
Eye: incomplete closure
Forehead: none

28
Q

HB V

A

Severe. Minimally perceptible motion. Asymmetry at rest
Mouth: slight
Eye: incomplete closure
Forehead: none

29
Q

HB VI

A

No movement

30
Q

Bell’s Palsy: etiology, diagnosis

A

Thought to be viral neuropathy from HSV
Paralysis/paresis all facial mm one side
Sudden onset
No signs of CNS disease, ear disease, parotid mass (this is a diagnosis of exclusion)

31
Q

Presentation of Bells

A

Follows viral prodrome (3-5d) and peak in sx at 48 hr

Wide palpebral fissure, taste, chewing difficulty, hyperesthesia trigeminal, facial pain, hyperacusis

32
Q

Percentage of Bells’ with FHx

A

14%

33
Q

Percentage of Bell’s who get recurrent facial paralysis

A

12%, ipsi or contralat

34
Q

Why we think HSV is the culprit

A

HSV present in geniculate ganglion of affected individuals (rare in NL pop)
Thought that it reactivated –> swell –> Bell’s

35
Q

How many acute facial palsies are due to Bell’s?

A

70%

36
Q

Causes of facial paralysis: Congenital

A

Mobius syndrome, congenital unilateral lower lip paralysis, Melkersson-Rosenthal syndrome, dystrophic myotonia

37
Q

Causes of facial paralysis: Traumatic

A

T bone fx, intrauterine compression, birth trauma/forceps delivery, facial contusions or lacerations, penetrating wounds to face or ear, iatrogenic injury, embolization for epistaxis, mandibular block anesthesia

38
Q

Causes of facial paralysis: Infection

A

Bell’s, herpes zoster oticus, OME, acute mastoiditis, MOE, TB, Lyme, HIV, mono, flu, encephalitis, malaria, syphilis, botulism

39
Q

Causes of facial paralysis: Idiopathic

A

Recurrent facial palsy

40
Q

Causes of facial paralysis: Neoplasia

A

cholesteatoma, carcinoma, acoustic neuroma, meningioma, facial neuroma, glomus jugulare/tympanicum, leukemia, hemangioblastoma, osteopetrosis, histiocytosis, rhabdomyosarcoma

41
Q

Causes of facial paralysis: Metabolic/systemic

A

DM, hyperthyroid, pregnant, autoimmune disorders, sarcoid, HTN

42
Q

Causes of facial paralysis: Neurologic

A

Guillan-Barre, MS, Millard-Gubler syndrome

43
Q

Central vs peripheral facial paralysis

A

Central (supranuclear) will spare the upper face on the side of the paralysis
Other signs of central: no emotional facial movement, decreased lacrimation, taste, salivation, tongue/hand dysfunction

44
Q

When to get MRI vs CT for facial paralysis

A

MRI w gad: inflammatory, neoplastic, non-traumatic

CT: traumatic paralysis, T-bone etiology (cholesteatoma)

45
Q

Schirmer’s test

A

Assess greater superficial petrosal innervation of lacrimal gland (PNS)
Filter paper strips in conj fornix, compare length of paper moistened over 5 minute period
Abnormal: <15mm lacrimation or 25% less than other eye

46
Q

Nerve Excitability Test: accurate at first?

A

Electrical impulse - muscle response to look for difference between sides. Not accurate in first 72 hours after onset since takes 3d for Wallerian degeneration to occur

47
Q

Maximal Stimulation Test

A

maximal rather than minimal stimulation

Becomes abnormal before the NET, but lack of objectivity, as measured by subjective facial muscle movement

48
Q

Electroneuronography (ENoG)

A

amplitudes of muscle summation potentials when supramaximal level of current applied
number of intact motor neurons determines result
Summation potential of 5-10% = 90% degenerated
Predicts who may benefit from decompression
Only accurate after 72 hours, but within 2wk to predict who will benefit from compression

49
Q

Electromyography

A

Eliminates False + results from other tests
Determines activity of muscle rather than nerve
Detects reinnervation potentials 6-12 wk before return of facial muscle function clinically evidenc
Cannot assess degeneration degree or recovery prognosis

50
Q

Audiometry for facial paralysis

A

Should be performed
CHL consistent with middle ear cause of paralysis
SNHL consistent with neoplasm ie acoustic neuroma, meningioma, facial nerve neuroma, affecting nerve at CPA or IAC

51
Q

Most important complication of CN VII paralysis

A

Exposure keratitis
Can lead to vision loss
Due to paralysis with inability to close eye completely, diminished tearing, loss of corneal sensitivity if coexistent CN V dysfunction
Red, itch, foreign body sensation, visual blurring

52
Q

How to avoid exposure keratitis

A

artificial tears 4-5x/d
ophthalmic lubricant before sleep, tape eyelid shut
Protect eye from wind, foreign body, drying (use glasses or moisture chamber)
Gold weight in eyelid if complete paralysis

53
Q

Crocodile tears

A

Fibers normally innervating salivary glands regenrate to innervate lacrimal gland
Gustatory tearing

54
Q

Approach to decompress CN VII at labyrinthine segment

A

middle fossa craniotomy

55
Q

When to consider surgery for VII paralysis

A

ENoG shows <10% # of motor fibers, tested prior to day 14

56
Q

Surgeries for different etiologies: trauma, acute OM, chronic OM, iatrogenic, idiopathic

A

Trauma/iatrogenic: decomp, anastamosis
Acute OM: Myringotomy
Chronic OM: Decomp, mastoidectomy
idiopathic: Decomp

57
Q

Can facial nerve be repaired if transected?

A

Yes, if >50% is transected, it should be repaired
Repair perineurium, exact end to end approximation
8-0 suture monofilament without tension
may graft with great auric or sural nerve
May jump graft from XII if proximal nerve absent
May cross graft from contralateral nerve

58
Q

How many T bone fxs are longitudinal? How many of these will involve facial nerve injury?

A

80-90% are longitudinal (parallel to petrous bone)

20% of these will have CN VII injury

59
Q

How many T bone fxs are transverse? How many of these have VII injury?

A

15% transverse

50% of these will injure VII

60
Q

With non-penetrating trauma, do you decompress or wait?

A

If paralysis is immediately following trauma, then likely laceration or impingement, so you may want to decompress

If paralysis develops in delayed fashion, medical management with steroids and electrophysiologic studies

61
Q

Two most common facial nerve tumors

A 
facial neuroma (schwannoma)
geniculate ganglion hemangioma (plexus surrounding ganglion)
62
Q

Herpes Zoster Oticus and Ramsay Hunt

A

intense ear pain, vesicles on EAC and concha
Reactivation of dormant herpes zoster in afferent sensory neurons of facial nerve
May progress to involve efferent motor axons of facial nerve –> facial palsy. This is called Ramsay Hunt
May have hearing loss/vertigo

63
Q

Treatment of HZO

A

steroids, acyclovir, pain meds, eye care

ENT Secrets (79 decks)

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