Quiz 3 (FN Disorders) Flashcards
which nerve is involved in eye movements assessed during vestibular testing
CN III Occulomotor
which brand of the facial nerve innervates the outer 2/3 of the tongue and can be sacrificed during ME surgery such as removal of a cholesteatoma
chorda tympani
osteopetrosis (bony displasia) is a disorder of aging that results in hardening of the cranial bones
false
____ syndrome is a rare congenital disorder with possible multifactorial inheritance in hypoplasia of CNs VI & VII
mobius
in the case of bell’s palsy, MEAR will be present if the lesion is ____ to the stapedius nerve
distal
a left facial nerve schwannoma will show an abnormal left ipsilateral response and an abnormal _____ contralateral response
right
largest CN with 3 major branches on each side of the pons, derivative of 1st pharyngeal arch
trigeminal CN V
innervates single muscle, superior oblique muscle of eye
cn iv
trochlear
lateral rectus of eye, most common overall cause of impairment is diabetic neuropathy
CN VI abducens
sensory fibers from posterior ⅓ of tongue, tonsils, pharynx, middle ear, & carotid sinus; supplies parasympathetic fibers to parotid gland through otic ganglion; supplies motor fibers to stylopharyngeus muscle; contributes to pharyngeal plexus
CN IX glossopharyngeal
innervates sternocleidomastoid & trapezius
CN XI accessory
longest course of all cn - head to abs & supplies diaphragm, derived from 4th pharyngeal arch
CN X vagus
supplies motor fibers to all muscles in tongue except palatoglossus muscle (accessory)
CN XII hypoglossal
what is the FN intracranial pathway
runs complex 3d course
originates in the facial motor nucleus in the anterior part of the pons
exits the BS at the pontomedullary junction
passes through the cerebellopontine angle to enter the IAC
ends by inserting into muscles of facial expression & stapedius muscle
what is the pathway of fn in IAC segment
exits bs & lies anterior to vestib nerve & superior to cochlear nerve
AICA runs bw CN 7 & 8 → provides vascular supply to this part of CN 7
chorda tympani runs bw 7 & 8 in IAC
after n enters IAC, it travels 8-10mm to the opening of IAC
in IAC, fn narrows to its lowest diameter & fallopian (facial) canal also narrows
what type of nerve is fn and where is it derived
mixed nerve
derived from 2 pharyngeal arch
what else is derived from the second pharyngeal arch
stapedius muscle
facial expressions, postauricular muscle, stapedial muscle (MEAR)
somatic motor
ear lobe & deep parts of the face
somatic sensory
what is somatic motor of fn
facial expressions, postauricular muscle, stapedial muscle (MEAR)
what is somatic sensory of fn
ear lobe & deep parts of the face
lacrimal & salivary glands
visceral motor
what is visceral motor of fn
lacrimal & salivary glands
chorda tympani nerve (anterior ⅔ of the tongue)
visceral sensory
what is visceral sensory of fn
chorda tympani nerve (anterior ⅔ of the tongue)
what supplies CN 7 in IAC
AICA
why is IAC segment a site that is at higher risk for entrapment/compression
in IAC, fn narrows to its lowest diameter & fallopian (facial) canal also narrows
canal narrowing is a common site for facial nerve entrapment and associated disorders
between the IAC & stylomastoid foramen
what is the fn pathway in the intratemporal portion
labyrinthine segment → goes through narrowing of bony canal in temporal bone
tympanic segment → forms superior part of oval window niche
mastoid segment → passes bw stapes & lateral semicircular canal & turns inferiorly to mastoid segment & exits temporal bone via stylomastoid foramen
stylomastoid artery (branch of postauricular arty) supplies this area of FN
common site of pathology: temporal bone fractures & Bell’s palsy
labyrinthine segment
what pathology is common in the labrythine segment
common site of pathology: temporal bone fractures & Bell’s palsy
fn injured here in pathologic processes & during ME surgery
tympanic surgery
what pathology occurs in the tympanic segment
fn injured here in pathologic processes & during ME surgery
shows variable branching patterns in the face
mastoid segment
what pathology does mastoid segment show
shows variable branching patterns in the face
course of FN makes it vulnerable to many neoplastic, traumatic, & infectious conditions
true
stylomastoid artery (branch of postauricular arty) supplies this area of FN
mastoid segment in the intratemporal segment pathway of FN
what supplies vascular supply to the mastoid segment in the intratemporal portion pathway of FN
stylomastoid artery (branch of postauricular arty) supplies this area of FN
incidence of NFP
~ 0.2%
NFP can be
congenital
prenatal acquired
postnatal acquired
what causes congenital NFP
developmental errors in embryogenesis
what causes prenatal acquired NFP
intrauterine trauma: forcep compression in delivery or facial compression against sacrum during labor
exposure to teratogens in utero (maternal rubella)
what causes postnatal acquired
most commonly trauma & infections that can also be seen in adults
AD genetic, a bony displasia that progresses/fluctuates and can cause blindness, HL, and facial paralysis (treatment: nerve decompression)
\
osteopetrosis
what is inheritance of osteopetrosis
AD
present at birth (congenital)
severity varies
milder than AR
AR of this disorder is more severe than AD
osteopetrosis
treatment of osteopetrosis
symptomatic
FN decompression if n entrapment results in facial dysfunction
aka Albers-SchÖnberg Disease
osteopetrosis
symptoms of osteopetrosis
involvement of CN II, V, VII, VIII that is progressive/fluctuating
multiple cranial neuropathies due to bone growth that compresses or entraps CNs
congenital facial paralysis
vision (even blindness) & HL (even deafness)
what is bony dysplasia
hardens & becomes denser
bone growth, “stone”
rare congenital disorder with hypoplasia/underdevelopment of CN 6 and 7 (multifactorial etiology with teratogens like drugs causing it)
mobius
Signs: bilateral facial paralysis, LR eye muscle not working, ID, musculoskeletal deformities (cross eyes, cant look to the side)
mobius
what is a teratogen
a substance that can cause or increase the risk of a birth defect in a baby. Teratogens can be drugs, alcohol, chemicals, or toxic substances. They can also be found in the environment, such as in street drugs, disease, or BPA
what is mobius
rare congenital hypoplasia of CN 6 & 7 nuclei
what is hypoplasia
condition where tissue or organ fails to grow to normal size
etiology of mobius
genetic → has multiple genes & modes of inheritance (multifactorial)
teratogens (exposure in utero) → cocain ergotamine
misoprostol
what is ergotamine (teratogen that can cause mobius)
alkaloid that is vasoconstrictor to treat migraines, induce birth, & prevent post-partum hemorrhage
what is misoprostol (teratogen that can cause mobius)
vasodilator that prevents stomach ulcers or treats tinnitus
what are signs & symptoms of mobius
bilateral facial paralysis
CN VI uni or bilateral paralysis (eye is turned in - cross eyed)
other cn deficits
deformities of extremities
musculoskeletal deformities
ID
what is the treatment for mobius
ophthalmologic consult
nerve reconstructive surgery
epidemiology of bell’s palsy
idiopathic
most common cause of acute unilateral facial paralysis
can be recurrent in small % of people
right side more often
affects both sexes equally (more frequency in women 10-19 yrs)
pregnancy increase risk 3 fold
pregnancy increases risk of bell’s palsy by 3 fold
most commonly during 3rd trimester
preeclampsia can increase occurrence
what is preeclampsia
disorder of pregnancy with high blood pressure and proteins in the urine
idiopathic, herpes virus also involved, begins with sensory then moves to motor
bells palsy etiology
what is etiology of bells pasly
idiopathic
usually diagnosed by exclusion (most common)
main infectious agent → herpes simplex virus
begins with sensory then moves to motor
what else can cause bell’s palsy that is rare
OM, CPA, parotid gland, or skull based tumors or metastatic lesions
explain how herpes simplex virus causes Bell’s palsy
entrapped → inflammatory response (swelling) leading to compression/ischemia of nerve at the meatal foramen and labyrthine segment
can cause n degeneration
diagnosis of Bell’s palsy
exclusionary diagnosis
what to look for in hx & clinical exam for bell’s palsy
partial/total unilateral facial paralysis → onset with 48 hr period
fever & stiff neck @ onset
no hl/vertigo
no other cranial neuropathy
eye drying (due to lack of eye closure & lacrimation)
recurrence is rare
spontaneous recovery w/in 3-6 mos in some
what is an exclusionary diagnosis
diagnosis of a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from history, examination or testing
what is done for diagnosis w/ in 3-6 mos of onset of paralysis
audiometric eval & hiv/lyme test if applicable
what do audio evals show for bell’s palsy
normal otoscopy, HL rare for pure tones, normal tymps, abnormal ARTs (proximal lesion to stapedius nerve), present ARTs (distal lesion to stapedius nerve)
Abnormal ARTS due to a lesion ________ to the stapedius nerve
proximal
Presence of ARTs indicates lesion ______ to the stapedius nerve
distal
what is done if no return of function after 3-6 mos post paralysis
ENog to assess n fiber degeneration
CT & MRI to differential diagnose from VIIN tumors
what are common FN tests used
ENoG, electromyography (EMG), nerve excitability test (NET), & max stim test (MST)
how does an enog work
A stimulating electrode is placed proximally over the nerve trunk and a second electrode is placed distally over muscle. Current is applied in the first electrode and response is detected in the second electrode. The response is measured bilaterally and the healthy side is compared to the weak side. The magnitude of the response on the weak side is calculated as a percentage of the response on the healthy side.
Degeneration greater than 90% is correlated with a poor prognosis
what is the adv of an enog
it is an objective measure of the amount of intact axons relative to the healthy side.
what is the treatment for bell’s palsy
nerve decompression → some surrounding bone may need removed
steroids in early course of disease
antiviral w/ steroids
eye care → prevents permanent damage w/ eye dryness
90% of degeneration happens w/in
2 wks of onset
what is the differential diagnosis for bell’s palsy
CPA/skull based tumors
vestib schwannoma
OM
Parotid gland tumors
most recover fxn w/ no medical or surgical intervention within
3-6 mos
young PT’s, partial paralysis & fxn recovery w/in 2 mos, distal lesion to stapedius nerve (lesion in mastoid or extratemporal segment of fn), EMG evidence of voluntary activity, ENoG shows <90% degeneration of electrically evoked muscle action potential after ~ two weeks of onset
good prognosis
what is a good prognosis for bell’s palsy
young PT’s, partial paralysis & fxn recovery w/in 2 mos, distal lesion to stapedius nerve (lesion in mastoid or extratemporal segment of fn), EMG evidence of voluntary activity, ENoG shows <90% degeneration of electrically evoked muscle action potential after ~ two weeks of onset
what is a poor prognosis for bell’s palsy
PT >65 yrs, >90% nerve degeneration within the first two weeks as diagnosed with ENoG & diabetic PT’s
PT >65 yrs, >90% nerve degeneration within the first two weeks as diagnosed with ENoG & diabetic PT’s
poor prognosis
why do diabetic PT’s show increased incidence/greater risk for Bell’s palsy?
because of a peripheral circulatory disorder that develops in the feeding vessels to the facial nerves
traumas that lead to fn dysfunction
temporal bone fractures
iatrogenic injuries (surgery)
lacerations
gunshot wounds
most common site is next to geniculate ganglion
HL → CHL, mixed SNHL
temporal bone fractures
common site is tympanic segment over oval window
injury from otosclerosis or cholesteatoma surgery
iatrogenic injuries from surgery
most common infection to affect the facial nerve
shingles
herpes zoster oticus
what is the most likely lesion where FN gets entrapped that causes symptom problems if there is tumor growth in children
facial nerve paralysis
what are infectious conditions that can affect the FN
malignant OE
facial paralysis caused by ME disease inflammation
chronic OM
herpes zoster oticus
etiology of malignant OE
invasion of pseudomonas pneumoniae & other bacteria into the soft tissue, cartilage & bone
treatment for malignant OE
infected tissue removal
FN decompression → if needed
antibiotics
what ME disease inflammations cause FN paralysis
acute suppurative OM
chronic OM
herpes zoster oticus
what is ramsay hunt syndome
aka herpes zoster oticus
caused by varicella virus (shingles)
remains dormant in the sensory ganglia of the fn & reactivates causing characteristic vesicles along the nerve pathway
symptoms of herpes/shingles
otalgia, HL, vertigo, more severe facial paralysis, & vesicles on concha, external canal or along sensory parts of 7th n
characteristic sites of pathology of shingles
labyrinthine segment of FN
can involve V, IX, X, XI
herpes zoster cephalicus
what is herpes zoster cephalicus
disease affecting CN’s including auditory, vestibular, trigeminal, glossopharyngeal & vagus; rare & involves cervical dermatomes
what is a dermatome
skin area supplied by a single spinal nerve
what is acute suppurative OM
gram-positive bacteria & haemophilus influenza (gram negative bacteria)
how does acute suppurative OM causae FN paralysis
caused by invasion into the facial canal through dehiscence causing inflammation w/ edema, compression & ischemic resulting to facial weakness
what is dehiscence
erosion or discontinuity in bony structure of facial canal causing a communication bw facial nerve & ME cavity
treatment for acute suppurative OM
myringotomy, antibiotics & trans-mastoid decompression if progression of nerve degeneration
FN paralysis secondary to this is common
can have paralysis w/ or w/out cholesteatoma
chronic OM
treatment of OM
urgent indication of surgery; tympano-mastoidectomy needed for chronic OM w/ FN decompression if FN is involved; removal of cholesteatoma if present on the nerve
treatment for herpes z o
antiviral med acyclovir
prognosis of herpes z o
less chance of spontaneous recovery than Bell’s palsy & recover is low even w/ steroids
what can be used to diagnose facial neuroma
audio eval
ENoG
CT & MRI
ABR
what will ARTs show w/ facial neuroma
abnormal ARTs w/ lesion PROXIMAL to stapedius n & present ARTs w/ lesion DISTAL to stapedius n (most likely in mastoid or extratemporal segment of FN)
what does pure tones & tymps show for facial neuroma
SNHL → due to cochlear n compression by tumor
normal tymps
what can ENoG show
if tumor is in CPA can be normal
can cause HL but no facial fxn effect
why do we use CT & MRI for facial neuromas
to differentiate the diagnosis bw VIII N tumors & other conditions
why use an abr for facial neuroma
determines whether tumor is acoustic or facial neuroma
Abnormal ARTS if a lesion is ______ to the stapedius nerve
proximal
ARTs present if a lesion is ______ to the stapedius nerve
distal
ARTs are ABNORMAL when measured on _______ side
AFFECTED
what would a R ART show for facial neuroma on R side
ART on R (right ispi & left contra) = absent
ART on L (left ipsi & right contra = normal?
if the tone is presented and measured on the probe side, then it is an _______ ART
ipsilateral
if the tone is presented on the earphone side and measured on the probe side, it is a ______ ART.
contralateral
should small facial neuromas be removed?
controversial
if facial tumor is slow growing what is management
conservative
observe only unless VII N paralysis or other symptoms occur (BS compression)
what are some managements of facial neuroma
observe
radiotherapy
decompression of fn if paralysis/other symptoms present
tumor resection w/ fn grafting
why do radiotherapy for facial neuromas
decreases the size before therapy
or used if it is causing pressure on critical structures (BS)
where does graft come from after facial tumor resection
sensory nerve
usually greater auricular or sural n
grafting results in excellent facial muscle tone post-surgery after 6-8 mos (some weakness remains)
true
sensory n in calf of leg & made of collateral branches of tibial n and common fibular n
sural n
what are differential diagnosis for facial neuromas
OM W/ CHL (w/ or w/out cholesteatoma
cholesteatoma (needs decompression of n & removal)
glomus tumor (paragangliomas → ME & jugular vein bulb)
meningiomas
acoustic neuroma
both VII & VIII n schwannomas reported in some cases of ____
NF2
