Term
| what are the 4 functions of the facial nerve? |
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Definition
| autonomic efferent (chordae tympani - stimulates saliva glands), autonomic afferent (chordae tympani - taste to ant 2/3 toungue, greater petrosal nerve - helps create tears), sensorimotor afferent (sensory nerve to external canal), sensorimotor efferent (peripheral branches of facial expression) |
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Term
| what is the pathway of the facial nerve to the facial nuclei from the cortex? |
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Definition
| the cortical projections originate in the precentral gyrus and most cross in the caudal pons to reach the facial nucleus (if pt can raise one eyebrow w/o raising the other, theirs prob don't cross and their forehead is more vulnerable to denervation if the innervation from one tract goes out). |
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Term
| what are the afferents to the facial nucleus? |
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Definition
| thalamic nucleus: facial expression, trigeminal nucleus: corneal reflex, acoustic nuclei: stapedial reflex, and visual system: blink reflex |
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Term
| what is the pathway of the facial nerve from the facial nuclei to the terminal branches? |
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Definition
| from the lower border of the pons to the internal auditory meatus (along w/CN 8), through the temporal bone, through the stylomastoid foramen (exits skull), and to the terminal branches. |
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Term
| what is the first branch off CN7 as it passes the internal auditory meatus? |
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Definition
| the greater superficial petrosal branch (stimulates lacrimal gland = tearing) which goes to the geniculate ganglion |
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Term
| what does the stapedial (2nd) branch off CN 7 do? |
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Definition
| stimulates the stapedial tendon - protects the ear from loud sounds. |
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Term
| what is the branch of CN 7 which stimulates the salivary glands (3rd branch)? what else does this branch do? |
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Definition
| chordae tympani, which also carries taste from the anterior 2/3 of the tongue. located almost between the ossicular chain and out the main trunk. |
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Term
| what is the CN 7 branch when it comes out the main trunk (4th branch)? |
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Definition
| the posterior auricular branch - sensory to the auricle and external auditory canal |
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Term
| what are the CN 7 branches of facial expression in order? |
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Definition
| temporal, zygomatic, buccal, mandibular, and cervical |
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Term
| what is the relationship between the facial nerve and CN7? |
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Definition
| CN 7 defines the two lobes of the parotid gland – doesn't have a fibrous capsule to encapsulate superficial and deep lobes. usually here there are 2 main branches of CN7: temporozygomatic and cervicofacial |
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Term
| what are the different tests which line up w/locations along the pathway of CN7? |
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Definition
| neurologic exam: supranuclear, nuclear, infranuclear cerebello-pontine angle. eng/audiologic/x-ray: internal auditory canal. tear test: geniculate ganglion. salivation/taste/stapedial reflex: tympanomastoid. facial movement: extra cranially |
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Term
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Definition
| transient episode of nerve damage w/no disruption of the nerve/nerve sheath (bruise) |
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Term
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Definition
| disruption of the neuronal axon, but maintenance of the myelin sheath (sprain) |
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Term
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Definition
| the nerve and nerve sheath are disrupted (break) |
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Term
| what is wallerian degeneration? |
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Definition
| the nerve is cut/crushed and the distal axon skeleton disintegrates/axon membrane breaks apart (24 hrs). a neurolemma remains and the proximal axon grows at 1 mm/day (96 hrs). (how a nerve grows back) |
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Term
| what is the best way of testing for nerve damage? |
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Definition
| EMG (but may take 10-14 days to appear) or the facial nerve stimulator test. nerve excitability, conduction latency, strength-duration curve are also possible tests. |
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Term
| what are the idiopathic causes of CN 7 paralysis? |
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Definition
| bell's palsy (dx of exclusion/*most common*) and melkerson-rosenthal syndrome |
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Term
| what are the traumatic causes of CN 7 paralysis? |
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Definition
| surgical trauma (ear/parotid/neck sx - commonly affects the marginal mandibular nerve - more common), temporal bone fracture, and facial trauma. |
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Term
| what are the infectious causes of CN 7 paralysis? |
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Definition
| herpes zoster oticus (vesicular, streaking rash), acute/chronic suppurative otitis media, malignant otitis externa, other (lyme, syphilis, meningitis, rubella, mononucleosis, other viruses) |
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Term
| what are the neoplastic causes of CN 7 paralysis? |
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Definition
| neuroma, meningioma, and central CNS/parotid malignancy |
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Term
| what is the schirmer nerve test? |
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Definition
| filter paper is applied to the lower lids to compare tear production over fixed time - tests the greater superficial petrosal nerve |
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Term
| how is the stapedial nerve tested? |
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Definition
| the stapedial acoustic reflex test, which can be tested via response recorded on a pressure meter to sound |
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Term
| how is the chordae tympani tested? |
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Definition
| 1) salivary flow test (cannulate wharton's ducts to collect saliva production over a fixed time). 2) electrogustometry: measure the amount of electricity needed to stimulate toungue sensation comparing sides. |
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Term
| how is facial expression tested? |
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Definition
| evaluate the voluntary movements of each peripheral branch: *eyebrow movement (raise eyebrow, if no corrugation), eye closure (**3rd CN opens eyes, 7th closes**), buccal function (purse lips, smile big, hold lip down [marginal mandibular nerve]), corneal reflex (cotton tip to sclera, should blink automatically), audiogram/electronystagmography (ENG - eval other nerves in the internal auditory canal), and a complete central neurologic exam |
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Term
| what does it mean if a pt can corrugate their eyebrows, blink, laugh w/full smile, but can't close eye? |
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Definition
| it's a central (cortical) problem vs a peripheral one |
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Term
| how would a pt w/a C7 supranuclear lesions present? |
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Definition
| the pt would have a spontaneous smile w/good tone and intact upper facial expression - but other neurologic deficits. dx: CVA, trauma |
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Term
| how would a pt w/C6-7 nuclear lesions present? |
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Definition
| the pt would have involvement of the 6th+7th CN and corticospinal tracts. dx: vascular, neoplastic, polio, MS, and encephalitis |
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Term
| how would a pt w/a C7 lesion at the level of the pontine angle present? |
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Definition
| involvement of the vestibular and cochlear portions of CN 8, in terms of CN7, taste/lacrimation/salivation are esp affected. later, CN5,9,10,11 may be also affected. dx: neuroma, hyperacusis, meningioma, fracture, cholesteatoma, arachnoid cyst (imaging). |
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Term
| how would a pt w/a C7 lesion at the level of the geniculate ganglion present? |
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Definition
| facial paralysis, hyperacusis, alteration of lacrimation, salivation and taste. dx: herpes zoster oticus, fracture, bell's palsy, cholesteatoma, neuroma, AVM, and meningoma. |
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Term
| how would a pt w/a C7 lesion at the level of the tympanomastoid present? |
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Definition
| facial paralysis, alteration in salivation and taste - but lacrimation is intact (distal to supra petrosal nerve). dx: bell's palsy, cholesteatoma, fracture, infection. |
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Term
| how would a pt w/a C7 lesion at the extracranial level present? |
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Definition
| facial paralysis (usually a branch is spared), intact salivation/taste and deviation of the jaw to the normal side. dx: trauma, tumor, parotid CA, and pharyngeal CA. |
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Term
| what is tx for CN 7 paralysis if identified as bell's palsy? |
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Definition
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Term
| what is tx for CN 7 paralysis if identified as nerve injury? |
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Definition
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Term
| what is tx for CN 7 paralysis if identified as due to otitis? |
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Definition
| myringotomy (aspirate through tympanic membrane), mastoidectomy, nerve decompression. if herpes zoster oticus: steroids. |
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Term
| how do bell's palsy pts usually present? |
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Definition
| insidious/sudden onset: "went to bed, felt fine but left the window open, woke up and face didn’t move (thought having a stroke)" |
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Term
| in tx of CN 7 lesions, how are complications of paralysis avoided? |
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Definition
| eye: early - tape eye shut at night and use artificial tears during the day, late - gold weights to upper lids and physical therapy for facial muscles (protects against corneal keratitis). muscle atrophy: stretch/exercise facial muscles, physical therapy. reconstruction: nerve grafting, cross face graft, and fascia sling. |
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