Facial Nerve Disorders Flashcards
innervation of the skeletal muscles
somatic motor
innervation of smooth muscles
visceral motor
sensation from viscera (includes taste and smell as they are associated w/ digestive tract
visceral sensory
Sensation from sensory organs, skin, skeletal muscles, and connective tissue
somatic sensory
Cranial nerves III (CNIII) (oculomotor), IV (trochlear), and VI (abducens) control the position of the ______ through various muscles.
eyeballs
helps to adjust and coordinate eye position during movement. Several movements assist with this process: saccades, smooth pursuit, fixation, accommodation, vestibulo-ocular reflex, and optokinetic reflex.
occulomotor
largest of the cranial nerves,
trigeminal nerve
what are the sensory nerves
olfactory
optic
vestibulocochlear
what are motor nerves
oculomotor
trochlear
abducens
accessory
hypoglossal
what are mixed nerves
trigeminal
fanical
glossopharyngeal
vagus
CN 1 2 3 are somatic or visceral and motor or sensory?
cn 1 is visceral sensory
cn 2 and 3 are somatic sensory
CN 3, 4, 6, 11, 12 are somatic or visceral and motor or sensory?
all are somatic motor
cn 3 is visceral motor
cn 5, 7, 9, 10 are somatic or visceral and motor or sensory?
7,9, 10 are all 4
5 is somatic motor and somatic sensory
muscles of facial expression
furrowing forehead, raising eyebrow, pursing lips, closing eyes
somatic motor innervaton
responsible for PAM (post auricular muscle reflex)
postauricular muscle
somatic motor innervation
muscles of facial expression
postauricular muscle
stapedius muscle
ME acoustic reflex
stapedius
visceral motor innervation
lacrimal and salivary glands
tear ducts
lacrimal
taste in anterior 2/3 of tongue (chorda tympani nerve)
visceral sensory innervation
posterior eac, concha, ear lobe, deep parts of face
somatic sensory innervation
mixed nerve derived from the second pharyngeal arch
facial nerve
runs a complex three-dimensional course
facial nerve
facial nerve course in cranium
Arises from the anterior part of the pons
Exists the brainstem at the pontomedullary junction
Passes through the cerebellopontine angle (CPA) to enter the IAC
This canal narrowing is a common site for facial nerve entrapment and associated disorders
Internal auditory canal or meatus (meatal) segment
runs between the VII and VIII N and provides vascular supply to this segment of the VII nerve
AICA
branch of VII N) lies between the VII and VIII N in the IAC
chorda tympani
Common site of pathology; temporal bone fractures & Bell’s palsy
Labyrinthine segment aka Intratemporal portion
what are intratemporal portions of facial nerve
labyrinthine segment
tympanic segment
mastoid segment
The facial nerve is readily injured here in pathologic processes and during ME surgery
tympanic segment
It shows variable branching patterns in the face
mastoid segment
exits the temporal bone via the stylomastoid foramen
mastoid segment
The course of the facial nerve makes it vulnerable to many
neoplastic, traumatic, and infectious conditions.
The incidence of newborn facial paralysis is _______%
~ 0.2%
Pediatric facial nerve paralysis can be
Congenital
Prenatal acquired
Postnatal acquired
what is congenital pediatric fn paralysis
Developmental errors during embryogenesis
what is prenatal acquired pediatric fn paralysis
Typically, due to intrauterine trauma, for example,
Forceps compression during delivery or compression of the side of face against the sacrum during labor
Fetal exposure to teratogens, for example,
Maternal rubella
what is postnatal pediatric fn paralysis
Many of the same conditions that can affect adults
Most commonly trauma and infections
also called Albers-SchÖnberg Disease
Osteopetrosis
what is osteopetrosis
an ad genetic conditionpresent at birth with varying severity and is a milder form than the AR condition, which is more severe
It is a bony dysplasia; the bones harden and become denser
Causes multiple cranial neuropathies because of bony obliteration of neural foramina with entrapment and compression of cranial nerves
osteopetrosis
Progressive or fluctuating involvement of CN II, V, VII, VIII in osteopetrosis
Congenital facial paralysis
Vision (even blindness) and hearing loss (even deafness) are common
treatment for osteopetrosis
Symptomatic
Facial nerve decompression if nerve entrapment and associated facial dysfunction
bony dysplasia
abnormal growth-dense bone
Rare congenital disorder associated with hypoplasia of 6th (Abducens – moves the eye laterally) and 7th (Facial) cranial nerve nuclei
Mobius syndrome
somatic efferent nerve that, in humans, controls the movement of a single muscle, the lateral rectus muscle of the eye, which moves the eye sideways, away from the nose.
Abducens (CN VI)
A condition in which tissue or an organ of the body fails to grow to normal size.
Hypoplasia
what is etiology of Mobius syndrome
Genetic with multiple genes and modes of inheritance (multifactorial)
Exposure in utero to teratogens such as
Cocaine
Ergotamine
Misoprostol (synthetic prostaglandin E1
alkaloid used as a vasoconstrictor to treat migraine, induce childbirth, and prevent post-partum hemorrhage
ergotamine
Vasodilator used to prevent stomach ulcers & sometimes used as a treatment for tinnitus
Misoprostol (synthetic prostaglandin E1)
symtpoms of mobius syndrom
Congenital facial diplegia (bilateral facial paralysis)
Associated CN VI unilateral or bilateral paralysis
Other cranial nerve deficits
Deformities of extremities
Musculoskeletal deformities
Intellectual disability
mobius treatment
Ophthalmologic consultation
Nerve reconstructive surgery
most common cause of acute unilateral facial paralysis
Accounting for approximately 60 to 75% of such cases
Although bilateral facial paralysis can also occur, the occurrence rate is <1% when compared to unilateral
Bell’s palsy
It can also be recurrent in ~ 4 to 14% of affected individuals
Right side is generally affected more often, ~ 63% of the time
bells palsy
affects both sexes equally
Although the condition is more frequent in younger women (aged 10-19) compared to the same age group of men
bells palsy
Pregnancy can increase the risk threefold, most commonly during the third trimester
Preeclampsia can increase the risk of occurrence
bell’s palsy
(disorder of pregnancy with high blood pressure and proteins in the urine)
preeclampsia
etiology of bells palsy
Idiopathic (most common - diagnosis of exclusion)
Herpes simplex virus (main infectious agent)
Rarely caused by a otitis media, cerebello-pontine angle (CPA), parotid gland or skull-based tumors, or metastatic lesions
Begins with the sensory fibers and then involves motor fibers
Inflammatory response (especially swelling) leading to compression/ischemia of the nerve at the meatal foramen and labyrinthine segment
Nerve degeneration can occur
entrapment from herpes simplex virus
a 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
exclusionary diagnosis
how to diagnose bells palsy
Onset of partial/total unilateral facial paralysis during a 48-hour period
Fever and neck stiffness at the onset
No hearing loss or vertigo
No other cranial neuropathy
Normal head and neck examination
Drying of eye due to decreased eye closure and lack of lacrimation
Rare cases of recurrence
Some spontaneous recovery should be noted within 3 to 6 months in all patients
what is audio findings of bells palsy
normal otoscopy
HL is rare in pure tones
normal tymps
ABNORMAL ARTS or PRESENT ARTs
Abnormal ARTS due to a lesion
proximal to the stapedius nerve
Presence of ARTs indicates
lesion distal to the stapedius nerve
Facial nerve tests most commonly used today include
electroneurography (ENOG) - most useful, electromyography (EMG), the nerve excitability test (NET), and the maximum stimulation test (MST)
what is ENOG
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.
what is the advantage of ENOG
objective measure of the amount of intact axons relative to the healthy side. Degeneration greater than 90% is correlated with a poor prognosis.
what is done if function doesn’t return 6 mos post paralysis
ENOG to assess degeneration of nerve fibers
CT & MRI - for differential from VII n tumors
treatment for bells palsy
Decompression of the nerve is indicated when > 90% degeneration occurs within 2 weeks of onset
Steroids indicated early in the course of the disease
Acyclovir (antiviral) with steroids (inconsistent data re: benefits)
Eye care to prevent permanent damage due to dryness of eye
involves relieving pressure on the nerve possibly by removing part of the surrounding bone
Decompression
what are differential diagnoses for bells palsy
CPA or skull-based tumors
Vestibular schwannoma
Otitis media
Parotid gland tumors
what is prognosis of bells palsy
Majority of patients recover function within 3 to 6 months with no medical or surgical intervention except eye care as needed
what factors lead to good prognosis with recovery of function
younger patients
partial paralysis &recovery within 2 mos
intact ART
EMG evidence of voluntary activity
ENOG shows <90% degeneration of electrically evoked muscle action potential after about two weeks of onset
poor prognosis of recovery of function for bells palsy
Patients older than 65 years
Greater than 90% nerve degeneration within the first two weeks as diagnosed with ENoG
Diabetic patients
why diabetic pt’s for bells palsy poor prognosis
because of a peripheral circulatory disorder that develops in the feeding vessels to the facial nerves
injury during surgical procedures
iatrogenic injury
Incidence 0.5 to 4%
The most common site of injury is the tympanic segment over the oval window; e.g., injury during otosclerosis and cholesteatoma surgery
iatrogenic injury
Most common site of injury is adjacent to the geniculate ganglion
Hearing loss (conductive, mixed or SNHL) is common
temporal bone fractures
what are traumas causing fn disorders
temporla bone fractures
iatrogenic injury
lacerations
gunshot wounds
Invasion of pseudomonas pneumoniae and other bacteria into the soft tissue, cartilage, and bone
etiology of malignant otitis externa
treatment of malignant otitis externa
Debridement of infected tissue
Decompression of facial nerve when needed
Antibiotics
Caused by gram-positive bacteria and Haemophilus influenzae
Invasion into the facial canal through a dehiscence may evoke an inflammatory response with edema, compression, and ischemia resulting in facial weakness
acute suppurative otitis media
treatment of facial paralysis secndary to inflammatory ME disease
Myringotomy
Appropriate antibiotics
Trans-mastoid decompression if nerve degeneration is progressive
Facial nerve paralysis secondary to _____ is fairly common
Paralysis can occur with or without cholesteatoma
chronic otitis media
treatment of otitis media
urgent indication for surgical intervention
Tympano-mastoidectomy is appropriate for the chronic ear infection followed by decompression of involved facial nerve
Removal of cholesteatoma, if present, adherent to the nerve
Caused by the varicella zoster virus (herpes family) - shingles
Herpes zoster oticus (Ramsay-Hunt Syndrome)
signs of Herpes zoster oticus (Ramsay-Hunt Syndrome)
Otalgia and severe pain
Vesicular eruption on the concha and/or external canal and along the sensory distribution of 7th cranial nerve
Facial paralysis that tends to be more severe
Hearing loss
Vertigo
Higher frequency of complete degeneration of the facial nerve
site of pathology of herpes
Labyrinthine segment of the facial nerve
Can involve CNs V, IX, X, XI
Herpes zoster cephalicus, which is rare and involves cervical dermatomes (skin areas)
treatment for herpes
antiviral medication, Acyclovir
prognosis of herpes
Less chances of complete spontaneous recovery than Bell’s palsy
Chances of recovery low even with steroid administration
are benign neoplasms of schwann cells
They comprise < 1% of all intrapetrous mass lesions
Primary facial neuromas or schwannomas
symptoms of facial neuroma
Facial weakness (2/3 of all cases)
Most facial weakness or paralysis is gradual but sudden onset of paralysis has been reported
Hearing loss (~ 50% of all patients)
Can be SNHL, conductive, or mixed depending on tumor location
Other symptoms, in 10 to 15% of cases
Tinnitus
Otorrhea
Ear canal mass
Otalgia
Vestibular symptoms
If the lesion is on the mastoid segment of CN VII and invading the ME cavity, ear canal, or in the tympanic portion, a _______ is possible
conductive hearing loss
what is tumor location of facial neuroma
variable
58% in the tympanic segment
48% in the vertical segment (lesion proximal to stapedius nerve)
42% in the labrynthine segment and geniculate body
30% in the IAC
19% in the CPA
14% in the stylomastoid foramen
If tumor is confined to IAC or CPA, ______ facial symptoms maybe present
no
audios for facial nerve neuromas
Pure-tone audiometry – generally SNHL due to cochlear nerve compression by the tumor
Immittance audiometry
Normal tympanogram
Abnormal ARTS due to a lesion proximal to the stapedius nerve
Presence of ARTs indicates lesion distal to the stapedius nerve
Lesion likely in the mastoid or extratemporal segment of the facial nerve
determine if a tumor is an acoustic or facial neuroma
abr
ARTs are abnormal whenever measured on the affected side
true
Whenever an ART is measured in the right ear (right ipsilateral and left contralateral) ARTs are absent
true
management of facial nerve
Controversy over whether or not to surgically remove small facial neuromas
Radiotherapy to decrease tumor size before surgery or if causing pressure on critical structures such as the brainstem
Decompression of facial nerve if paralysis or other symptoms
Tumor resection if warranted, with facial nerve grafting from a sensory nerve
sensory nerve in the calf region (sura) of the leg. It is made up of collateral branches of the tibial nerve and common fibular nerve.
sural nerve
differential diagnosis of facial neuroma
Otitis media with conductive hearing loss
With or without cholsteatoma
Cholesteatoma
Requires prompt decompression of the VII N and resection of the cholestatoma
Glomus tumor (Paragangliommas – ME & jugular vein bulb)
Meningiomas
Tumor of the meninges
`Acoustic neuroma (vestibular schwannoma)
Both VII and VIII nerve schwannomas have been reported in some cases of NF2
