21 - CN VII palsy

Where is the CN VII nucleus located?

in the pons

How does CN VII receive supranuclear input?

supranuclear input innervate both nuclei (bilateral) → more input contralaterally for upper muscles of facial expression and less input contralaterally for the lower muscles of facial expression

What are the 4 main components of the facial nerve?

1. branchial motor

2. visceral motor

3. special sensory

4. general sensory

Where do the motor branches of CN VII travel?

1. exits brainstem at stylomastoid foramen

2. enters posterior parotid gland and divides into upper and lower divisions → subdivided further

What are the 5 motor branches of the facial nerve?

1. temporal

2. zygomatic

3. buccal

4. mandibular

5. cervical

How do you examine CN VII function?

1. facial asymmetry

2. blink pattern

3. lagophthalmos

4. look at facial emotional response vs response to command

5. have patient force eyes closed while examiner attempts to open

How do you assess if CN VII damage is supra or infra nuclear?

supranuclear if:

1. involuntary/emotional response is better than voluntary

2. can still wrinkle forehead/raise brow

What are the causes of nuclear lesions of CN VII?

1. vascular

2. infection

3. trauma

4. tumors

How does a nuclear lesion of CN VII present?

complete ipsilateral upper and lower facial paralysis

What are the associated signs of a CN VII nuclear lesion? What causes this?

1. other CN involvement

2. hemiparesis or anesthesia

due to pontine disturbances → can affect CN VI and corticospinal tract

What CN can cerebellopontine angle lesions affect?

CN V-VIII

What can be the presentation of a cerebellopontine angle lesions?

1. loss of corneal sensation

2. abducens defect

3. facial paresis

4. ipsilateral facial pain

5. tinnitus

6. vertigo

7. ipsilateral retroauriclar pain

8. deafness

How does a peripheral/infranuclear CN VII lesion present?

if damage prior to 5 branches → complete ipsilateral facial paralysis + all voluntary + emotional movements lost

if damage after 5 branches → regional paralysis of muscles supplied by lesioned branch

may have associated decreased taste/lacrimation/hearing

what are the causes of peripheral lesions?

1. Bell's palsy

2. malignancy

3. infection → HZV, middle ear, meningitis, Lyme disease

What is the Bell's palsy?

idiopathic lesion of VII at or after the stylomastoid foramen

what is the most common isolated peripheral CN VII disorder?

Bell's palsy

What causes bell's palsy?

suspected after a cold or likely related to HSV

What are the signs of bell's palsy?

1. all actions of face impaired (including emotional/reflexive)

2. facial asymmetry

3. smooth nasolabial folds

4. inability to close lid

5. widened palpebral fissure

6. epiphora

7. may have impaired taste

what causes the widened palpebral fissure in Bell's palsy?

unopposed action of LPS

what causes epiphora in Bell's palsy?

lack of punctal apposition to globe

What is the time course of bell's palsy?

spontaneous complete recovery in majority, generally in 2-4 months

What can happen in recovery of bell's palsy?

1. misdirection → crocodile tears, blink with movement of mouth

2. muscle spasms (rare)

How do you diagnose a bell's palsy patient?

rule out other CN involvement → check corneal sensation

explore other potential causes..Dx of exclusion!

What is the management for bell's palsy?

1. corneal lubrication

2. lid weights or surgery

3. systemic steroids/antivirals

4. consider neuro consult → esp if acute onset

what are the presentations of Ramsay-Hunt syndrome?

1. VII palsy with facial paralysis

2. pain in ear

3. vesicles in ear

What is the most common form of bilateral blepharospasm?

isolated essential blepharospasm

What are the causes of bilateral blepharospasm?

1. isolated essential blepharospasm

2. parkinsons

3. huntingtons

4. MS

5. tourettes

6. NM disease

What is the cause of isolated essential blepharospasm?

idiopathic

Who gets isolated essential blepharospasm?

45-70 years

female > male

What are the signs of isolated essential blepharospasm?

1. initial symptom is excessive blinking

2. worsens in social settings, driving, lights, stress

3. early on gets relief from humming, singing, sleeping

What is the treatment for isolated essential blepharospasm?

1. anti-anxiety meds

2. botox

3. surgery

What is the cause of hemifacial spasm?

compression/injury to CN VII as it exits the brainstem → spontaneous firing of CN VII

What are the signs of hemifacial spasm?

1. unilateral involuntary bursts of muscle activity lasting seconds to minutes

2. typically progresses from twitching of lid to spasm of facial muscles

What is the management of hemifacial spasm?

1. MRI to rule out lesion

2. botox injections

3. suboccipital craniectomy → place non-absorbing sponges between offending vessel and nerve