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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
HB II
``` Mild dysfunction Slight weakness close inspection, normal symmetry/tone Slight asymmetry mouth Complete closure eye minimal effort Moderate to good forehead ```
26
HB III
``` Obvious, not disfiguring asymmetry Normal symmetry/tone Mouth: slight weak maximum effort Eye: complete closure with effort Forehead: slight to moderate ```
27
HB IV
Moderately Severe. Obvious weakness, possible dysfunction Mouth: asymmetric maximum effort Eye: incomplete closure Forehead: none
28
HB V
Severe. Minimally perceptible motion. Asymmetry at rest Mouth: slight Eye: incomplete closure Forehead: none
29
HB VI
No movement
30
Bell's Palsy: etiology, diagnosis
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
Presentation of Bells
Follows viral prodrome (3-5d) and peak in sx at 48 hr | Wide palpebral fissure, taste, chewing difficulty, hyperesthesia trigeminal, facial pain, hyperacusis
32
Percentage of Bells' with FHx
14%
33
Percentage of Bell's who get recurrent facial paralysis
12%, ipsi or contralat
34
Why we think HSV is the culprit
HSV present in geniculate ganglion of affected individuals (rare in NL pop) Thought that it reactivated --> swell --> Bell's
35
How many acute facial palsies are due to Bell's?
70%
36
Causes of facial paralysis: Congenital
Mobius syndrome, congenital unilateral lower lip paralysis, Melkersson-Rosenthal syndrome, dystrophic myotonia
37
Causes of facial paralysis: Traumatic
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
Causes of facial paralysis: Infection
Bell's, herpes zoster oticus, OME, acute mastoiditis, MOE, TB, Lyme, HIV, mono, flu, encephalitis, malaria, syphilis, botulism
39
Causes of facial paralysis: Idiopathic
Recurrent facial palsy
40
Causes of facial paralysis: Neoplasia
cholesteatoma, carcinoma, acoustic neuroma, meningioma, facial neuroma, glomus jugulare/tympanicum, leukemia, hemangioblastoma, osteopetrosis, histiocytosis, rhabdomyosarcoma
41
Causes of facial paralysis: Metabolic/systemic
DM, hyperthyroid, pregnant, autoimmune disorders, sarcoid, HTN
42
Causes of facial paralysis: Neurologic
Guillan-Barre, MS, Millard-Gubler syndrome
43
Central vs peripheral facial paralysis
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
When to get MRI vs CT for facial paralysis
MRI w gad: inflammatory, neoplastic, non-traumatic | CT: traumatic paralysis, T-bone etiology (cholesteatoma)
45
Schirmer's test
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
Nerve Excitability Test: accurate at first?
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
Maximal Stimulation Test
maximal rather than minimal stimulation | Becomes abnormal before the NET, but lack of objectivity, as measured by subjective facial muscle movement
48
Electroneuronography (ENoG)
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
Electromyography
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
Audiometry for facial paralysis
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
Most important complication of CN VII paralysis
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
How to avoid exposure keratitis
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
Crocodile tears
Fibers normally innervating salivary glands regenrate to innervate lacrimal gland Gustatory tearing
54
Approach to decompress CN VII at labyrinthine segment
middle fossa craniotomy
55
When to consider surgery for VII paralysis
ENoG shows <10% # of motor fibers, tested prior to day 14
56
Surgeries for different etiologies: trauma, acute OM, chronic OM, iatrogenic, idiopathic
Trauma/iatrogenic: decomp, anastamosis Acute OM: Myringotomy Chronic OM: Decomp, mastoidectomy idiopathic: Decomp
57
Can facial nerve be repaired if transected?
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
How many T bone fxs are longitudinal? How many of these will involve facial nerve injury?
80-90% are longitudinal (parallel to petrous bone) | 20% of these will have CN VII injury
59
How many T bone fxs are transverse? How many of these have VII injury?
15% transverse | 50% of these will injure VII
60
With non-penetrating trauma, do you decompress or wait?
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
Two most common facial nerve tumors
``` facial neuroma (schwannoma) geniculate ganglion hemangioma (plexus surrounding ganglion) ```
62
Herpes Zoster Oticus and Ramsay Hunt
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
Treatment of HZO
steroids, acyclovir, pain meds, eye care

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