Facial Nerve

Question 1

Branchial motor (special visceral efferent)

Answer 1

Supplies the muscles of facial expression; posterior belly of digastric muscle; stylohyoid, and stapedius.

Question 2

Visceral motor (general visceral efferent)

Answer 2

Parasympathetic innervation of the lacrimal, submandibular, and sublingual glands, as well as mucous membranes of nasopharynx, hard and soft palate.

Question 3

Special sensory (special afferent)

Answer 3

Taste sensation from the anterior 2/3 of tongue; hard and soft palates

Question 4

General sensory (general somatic afferent)

Answer 4

General sensation from the skin of the concha of the auricle and from a small area behind the ear.

Question 5

DifferenSal for Acute Facial Nerve Paralysis

Answer 5

•  Polyneuritis 
–  Bell’s palsy
–  Herpes zoster
–  Guillan Barre syndrome
–  Autoimmune disease
–  Lyme disease
–  HIV
–  Kawasaki disease 

•  Trauma
–  Temporal bone
–  Barotrauma
–  Birth trauma

•  Otitis Media
–  Acute bacterial
–  Chronic bacterial
–  Cholesteatoma

•   Sarcoidosis
•   Melkersson-‐‐Rosenthal

•  Neurologic disorders
–  HIV
–  Cerebrovascular disorders: central or peripheral

Question 6

Differential for Chronic or Progressive Facial Nerve Paralysis

Answer 6

•  Malignancies
–  Primary parotid tumor
–  Metastatic tumor

•  Benign tumors
–  Schwannoma
–  Glomus tumor

•  Cholesteatoma

Question 7

Examination of Patient with Facial Paresis/Paralysis

Answer 7

•  History 
–  Time of onset
–  Precipitating factors
–  Speed of progression
–  Associated symptoms 
•  Physical Examination 
–  House-‐‐Brackmann classifications 
•  Topodiagnostic tests
•  Electrophysiologic tests
•  Lab tests PRN
•  Imaging

Question 8

Grading of Facial Nerve FuncSon
House-‐‐Brackmann Scale
(Otolaryngology Head Neck Surgery, 1985)

Answer 8

•  Grade I – Normal

•  Grade II – Mild
– Gross: slight weakness noticeable on close inspection
– At rest: normal symmetry and tone
– Motion: Forehead – moderate to good; Eye – complete closure with minimum effort; Mouth – slight asymmetry

•  Grade III – Moderate
– Gross: obvious but not disfiguring asymmetry; may have hemifacial spasm
– At rest: normal symmetry and tone
– Motion:  Forehead – slight to moderate movement;  Eye – complete closure with effort; Mouth – slightly weak with maximum effort

•  Grade IV – Moderately severe
– Gross: obvious weakness and/or disfiguring asymmetry
– At rest: normal symmetry and tone
– Motion:  Forehead – no movement; Eye – incomplete closure; Mouth – asymmetric with maximum effort

•  Grade V – Severe
– Gross: only barely perceptible motion – At rest: asymmetry – Motion: Forehead – no movement •  Eye – incomplete closure •  Mouth – slight movement

•  Grade VI – Total Paralysis
– No movement

Question 9

Topodiagnostic Tests of Facial Nerve Function

Answer 9

•  Schirmer’s Test of Lacrimal Function •  Stapedial Reflex •  Electrogustometry •  Salivary Flow

Question 10

Electrodiagnostic Tests of Facial Nerve Function

Answer 10

•  Nerve excitability test
– Transcutaneous stimuli delivered over stylomastoid foramen
– Electrical pulses delivered at increasing current levels until facial twitch is noticeable

•  Maximum excitability test
– Transcutanteous stimuli looking for twitch – Increase current to get maximum response

•  Electromyography (EMG)
– Recording of spontaneous and voluntary muscle potentials
– Needle electrodes in facial muscle groups
– May help to predict recovery

•  Electroneuronography (ENoG)
–  Stimulating electrodes deliver suprathreshold electrical stimuli
–  Recording electrode measures compound muscle action potential
–  Reduction in response amplitude reflects number of damaged motor fibers
–  Best 3 days to 3 weeks
–  Prognostic value
•  >90% degeneration at 3 weeks -‐‐ surgery
•  <90% degeneration at 3 weeks -‐‐ chance for good recovery

Question 11

Bell’s Palsy overview

Answer 11

•  Most common acute mono‐neuropathy, or disorder affecting a single nerve
•  Most common diagnosis associated with facial nerve paresis (weakness) or paralysis (complete loss of movement) of unknown cause.
•  Causes partial or complete inability to voluntarily move facial muscles on the affected side of the face.
•  The facial paresis/paralysis that occurs in Bell’s palsy may cause: Significant oral incompetence; Eye injury; Long term poor outcomes can occur, and can be
devastating to the patient
•  Diagnosis of exclusion
•  Not every patient with facial paralysis/paresis will have Bell’s Palsy
•  Variations in care; controversy over best treatment options
•  Numerous test available; many are of questionable benefit.
•  Rapid in onset (<72 hours)
•  Dx when no other medical etiology is identified as a cause of facial weakness.
•  Bilateral Bell’s palsy is rare.
•  Currently, the cause is unknown
•  Typically, self-‐‐limiting
•  Can occur in anyone, but is most common in
15-‐‐45 y/o, and those with risk factors

Question 12

Bell’s Palsy Risk Factors, Epidemiology, Prognosis

Answer 12

•  Risk Factors:
– Pregnancy – Severe preeclampsia – Obesity – Hypertension and chronic hypertension – Diabetes – Upper respiratory ailments

•  Epidemiology
– 11.5-‐‐53.3 per 100,000
– 35,000 to 100,000 cases annually in the US. – 30% incomplete paralysis at presentation – 70% of cases of facial paralysis/paresis
•  (30% of cases are not Bell’s Palsy)

The emotional impact of this condition should not be underestimated.

Prognosis for Bell’s Palsy
•  Majority have spontaneous, good recovery at 3-‐‐6 months
•  Best prognosis
–  Never at grade VI –  Signs of recovery at 2 months –  EMG evidence of voluntary activity –  Present acoustic reflex –  < 90% degeneration on ENoG at 2 week point
•  Worst prognosis
–  Age >65 years –  Diabetes –  >90% degeneration on ENoG at 2 week point

Question 13

Bell’s Palsy Treatment and Management

Answer 13

•  Eye Care
–  Very important for Grade III or worse
–  Drying of eye 2° to ↓ eye closure and lacrimation → keratopathy and breakdown of the cornea
–  Daytime: artificial tears every 2 hours
–  Nightime: ophthalmic ointment and moisture chamber over eye
–  Temporary tarsorrhaphy (surgery to bring eyelids closer together) or gold weight

•  Medical Treatment
–  Steroid Rx – should be given in 72 hrs for >16 y/o
•  Prednisone -‐‐ 1mg/kg/day 7-‐‐10 days
–  Antiviral therapy used in combination with oral steroid by some

Bell’s Palsy: Surgical Treatment
•  Facial nerve decompression
–  Transmastoid –  Middle cranial fossa decompression
•  No clear evidence of efficacy.
–  Good outcomes for pts with incomplete paralysis
–  Lack of large trials
–  Diversity of patients in existing trials
–  Variable surgical approaches
–  Lack of efficacy compared to natural hx