Lecture 9- CN 7, Facial Nerve Flashcards
What are the different segments of the facial nerve?
- Brainstem
- Pontine
- Meatal
- Labyrinthine
- Tympanic
- Mastoid
- Extratemporal
What are the different components of the facial nerve?
- Branchial motor (special visceral efferent)
- Visceral motor (general visceral efferent)
- Special sensory (special afferent)
- General sensory (general somatic afferent)
What is the branchial motor component of the facial nerve?
- Supplies the muscles of facial expression
- Posterior belly of digastric muscle
- Stylohyoid and stapedius
What is the visceral motor component of the facial nerve?
Parasympathetic innervation of the lacrimal, submandibular, and sublingual glands, as well as mucous membranes of nasopharynx, hard and soft palate
What is the special sensory component of the facial nerve?
Taste sensation from the anterior 2/3 of tongue; hard and soft palates
What is the general sensory component of the facial nerve?
General sensation from the skin of the concha of the auricle and from a small area behind the ear
What is the posterior auricular branch?
Pulls ears back, pulls scalp back
What is the temporal branch?
Pulls ear forward and raises ear, moves scalp forward, moves eyebrows medially and down
What is the temporal and zygomatic branch?
Closes eyelids and creases skin around eye
What is the zygomatic and buccal branch?
Elevates upper lip, upper corner of the mouth and nasolabial folds
What is the buccal branch?
Mouth movements, flares nostrils
What is the marginal mandibular branch?
Pulls skin of chin up
What is the cervical branch?
Pulls down at corner of the mouth
What is differential diagnosis for acute facial nerve paralysis?
- Polyneuritis
- Trauma
- Otitis media
- Sarcoidosis
- Melkersson-Rosenthal
- Neurologic disorders
What is differential diagnosis for chronic or progressive facial nerve paralysis?
- Malignancies
- Benign tumors
- Cholesteatoma
What should examination of a patient with facial paresis/paralysis consist of?
History
- Time of onset
- Precipitating factors
- Speed of progression
- Associated symptoms
Physical examination
- House-Brackmann classifications
Topodiagnostic
Electrophysiologic tests
Lab tests PRN
Imaging
What are the grades of the House-Brackmann scale?
Grade I: Normal
Grade II: Mild
Grade III: Moderate
Grade IV: Moderately severe
Grade V: Severe
Grade VI: Total Paralysis
What is grade I of the House-Brackmann scale?
Grade I: Normal
What is grade II of the House-Brackmann scale?
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
What is grade III of the House-Brackmann scale?
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
What is grade IV of the House-Brackmann scale?
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
What is grade V of the House-Brackmann scale?
Gross: only barely perceptible motion
At rest: asymmetry
Motion:
- Forehead: no movement
- Eye: incomplete closure
- Mouth: slight movement
What is grade VI of the House-Brackmann sclae?
No movement
What are topodiagnostic tests of facial nerve function?
- Schirmer’s Test of Lacrimal Function
- Stapedial Reflex
- Electrogustometry
- Salivary Flow
What is the nerve excitability test?
Transcutaneous stimuli delivered over stylomastoid foramen.
Electrical pulses delivered at increasing current levels until facial twitch is noticeable.
What is the maximum excitability test?
Transcutanteous stimuli looking for twitch.
Increase current to get maximum response.
What is electromyography (EMG)?
Recording of spontaneous and voluntary muscle potentials.
Needle electrodes in facial muscle groups.
May help to predict recovery.
What is 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
What is the prognostic value of ENoG?
> 90% degeneration at 3 weeks- surgery
<90% degeneration at 3 weeks- chance for good recovery
What is the presentation of Herpes Zoster Oticus?
- Severe pain
- Vesicles in concha
- Severe (grade V and VI) facial paralysis
- Frequently involves CN VIII giving hearing loss and vertigo
- May involve CN V, IX, X, XI, and XII
What is the cause of herpes zoster oticus?
Varicella zoster virus
What is the prognosis of herpes zoster oticus?
- Spontaneous recovery of CN VII function 22-31%
- ENoG prognositcation (not so good)
What are the treatment options for Herpes Zoster Oticus?
- Acycolvir ++
- Prednisone ?
- MCF decompression not justified
What are the presentations of a facial neuroma?
- Facial weakness
- Hearing loss in 50%
- 10-15% have tinnitus, ear canal mass, pain, vestibular Sx, and otorrhea
What are some pediatric facial nerve disorders?
- Congenital paralysis
- Prenatal acquired paralysis
- Postnatal acquired paralysis
- Mobius syndrome
- Hemifacial microsomia
- Prenatal acquired paralysis
What are some postnatal acquired pediatric facial nerve disorders?
- Osteopetrosis - Albers-Schonbergs disease
- Melkersson- Rosenthal syndrome
