quiz 3 Flashcards
facial nerve (CN 7)
a mixed nerve derived from the second pharyngeal arch
-somatic and visceral motor/sensory innervation occurs
somatic motor innervation
muscles of facial expression, post auricular muscle and stapedius muscle
-responsible for post auricular muscle reflex
-responsible for middle ear acoustic reflex
visceral motor innervation
lacrimal (tear ducts) and salivary glands
-hard to make tears if CN 7 is affected
visceral sensory innervation
taste within the anterior 2/3 of tongue
-chorda tympani nerve
somatic sensory innervation
posterior EAC, concha, ear lobe and deep parts of the face
what is the origin of CN 7
facial motor nucleus within the anterior pons
what is the insertion of CN 7
muscle of facial expression and stapedius muscle
what is the pathway of the facial nerve
arises from anterior pons, exits brainstem through pontomedullary junction, goes through cerebellopontine angle to enter the IAC, travels through meatal foramen, passes through the fallopian canal, forms superior aspect of oval window niche, then after passing stapes and SCC turns into the mastoid segment and exits through the stylomastoid foramen
what is the most common site for pathology along the facial nerve
when passing through the fallopian canal (labyrinth segment)
-narrowest diameter and causes a site for entrapment and associated disorders
what is the potential problem with the facial nerve pathway
it can be very variable from the CPA to IAC in how i runs it course
what ways can facial nerve disorders present in children
congenital (occurs during embryogenesis), prenatal acquired (intrauterine trauma or exposure) and postnatal acquired (many of the same conditions present in adults)
osteopetrosis
a rare AD genetic conditions that is present at birth with varying severity and presents with bony dysplasia
-cranial neuropathies due to bony obliteration of neural formania with the entrapment or compression of nerves
symptoms of osteopetrosis
congenital facial paralysis, vision issue (blindess can occur), HL (deafness can occur)
-due to involvement of CN 2, 5, 7 and 8
treatment of osteopetrosis
symptomatic treatment for symptoms and facial nerve decompression if nerve entrapment is associated with the issues presenting
mobius syndrome
a rare congenital disorder associated with hypoplasia of the 6th and 7th nerve
-genetic with multiple genes and modes of inheritance or can occur due to exposure in utero to teratogens such as cocaine
symptoms of mobius
congenital facial diplegia (paralysis), associated CN 6 paralysis, other cranial nerve deficits, deformities of extremities, musculoskeletal deformities, intellectual disability
treatment for mobius
ophthalmologic consolation and nerve reconstruction surgery
bell’s palsy
disorder that is the most common cause of acute unilateral facial paralysis
-can be idiopathic, due to being a diagnosis of exclusion meaning that this is what is diagnosed when presenting with facial paralysis
-can occur from herpes simplex virus which leads to compression of the nerve
-begins with sensory fibers and then involves more motor fibers
anything that causes ____________ will cause facial nerve paralysis
compression
how is a diagnosis of bell’s palsy given
history and clinical examination point to the correct diagnosis
-onset during a 48 hour period
-fever and neck stiffness at onset
-no HL or vertigo
-no other cranial neuropathy
-normal head and neck examination
-drying of eyes
-can be recurrent
audiologic evaluation of bell’s palsy
-normal otoscopy
-HL is rare
-normal tymps
-abnormal ARTs if lesion is proximal to stapedial nerve
-present ARTs if lesion is distal to stapedial nerve
if function has not retuned within 6 months post paralysis with bell’s palsy, what is waranted
CT scan and MRI as well as electroneurography to assess generation of nerve fibers
treatment for bell’s palsy
decompression of nerve, steroids indicated early in the course of the disease, antiviral with steroids and eye care to prevent damage
differential diagnosis for bell’s palsy
CPA or skull based tumors, vestibular schwannoma, otitis media, parotid gland tumors
good prognosis for bell’s palsy
younger patients, partial paralysis and recovery within 2 months, intact ARTs, less degeneration in ENoG
poor prognosis for bell’s palsy
patients older than 65, greater than 90% nerve degeneraion within first two weeks, and diabetic patients
what trauma can cause facial nerve deficits
temporal bone fractures, iatrogenic injuries, lacerations and gunshot wounds
malignant otitis externa
invasion of bacteria within the soft tissue
-treat with debridement of infected tissue, antibiotics and the decompression of the facial nerve when needed
acute suppurative otitis media
caused by bacteria and can lead to invasion into the facial canal through a dehiscence that may evoke an inflammatory response with edema or compression resulting in facial weakness
-treat with myringotomy, antibiotics and a trans mastoid decompression
chronic otitis media
facial nerve paralysis secondary to this is common
-needs surgical intervention such as a tympano-mastoidectomy followed by decompression of the facial nerve
herpes zoster oticus
caused by shingles
-presents with otalgia and pain, vesicular eruption on the concha and/or external canal and along sensory distribution of the 7th nerve
-treat with antiviral medication
-less change of complete spontaneous recovery than bell’s palsy
facial neruoma
primary facial neruomas or schwannomas are rare bengin neopalsms of schwann cells
-these are less common than schwannomas
symptoms of a facial neruoma
facial weakness, HL (any type), tinnitus, otorrhea, ear canal mass, otalgia, vestibular symptoms and you can see redness in the canal due to the masses needing a blood supply