Facial Nerve Disorders Flashcards
Innervations of facial nerve
Somatic Motor:
1 . Muscles of facial expression
2. Stapedius
3. Posterior belly of digastric
4. Stylohyoid
Somatic Sensory:
1. External ear (small area around concha of auricle)
Special Sensory:
1. Taste to anterior 2/3 of tongue
Parasympathetic
1. Submandibular and sublingual salivary glands
2. Lacrimal gland
Course of facial nerve
Arises from pons
-> Internal acoustic meatus
-> Facial canal
= Labyrinthine segment: 1st branch of facial nerve: greater petrosal nerve (lacrimal gland)
-> Tympanic segment: Runs in middle ear behind TM
= Mastoid segment: Branches of facial nerve: Nerve to stapedius and chorda tympani (anterior 2/3 of tongue, submandibular and sublingual glands)
-> Exits facial canal through stylomastoid foramen
= Branches of facial nerve:
Posterior auricular nerve, nerve to posterior belly of digastric, nerve to stylohyoid
-> Pierces parotid gland
-> Divides into 5 terminal branches:
Temporal
Zygomatic
Buccal
Mandibular
Cervical
What nerve runs with chorda tympani?
Lingual nerve
Clinical features of CN7 UMN lesions
- Contralateral weakness of lower half of face
- Preserved function in contralateral upper face (spares forehead)
- Loss of contralateral nasolabial fold
- Drooping of corner of mouth - Sensation of external auditory meatus
- Unaffected - Corneal reflex
- Preserved - Stapedius
- Unaffected - Taste and tears
- Unaffected
Clinical features of CN7 LMN lesions
- Ipsilateral weakness of upper + lower half of face
- Loss of (IP) frontal wrinkling
- Inability to fully shut (IP) eye
- Loss of (IP) nasolabial fold
- Drooping of (IP) corner of mouth - Sensation of external auditory meatus
- Decreased sensation - Corneal reflex
- Loss - Stapedius
- Hyperacusis - Taste and tears
- Decreased secretion of saliva and tears: Exposure Keratitis
- Loss of taste in anterior 2/3 of the ipsilateral tongue
(If lesion is before chorda tympani branches out)
Causes of CN7 UMN lesion
Tumour
Stroke: Bleed, infarct
Demyelination disease
Recovering Bell’s palsy (May look like forehead sparing)
Causes of CN7 LMN lesion
Behind the ear
- Mastoid surgery
- Mastoiditis
- Cholesteatoma surgery
On
- Ramsay hunt syndrome
- Malignant otitis externa
- Acute/chronic otitis media
Below
- Parotid tumour
- Parotid surgery
- Bell’s palsy
- Temporal bone fracture
Internal
- Middle ear disesae
- Glomus tumours
- Cerebellopontine angle tumour (acoustic neuroma)
Onset of Bell’s palsy
- Clinical Dx, Dx of exclusion
- Acute onset over a 48-72 hour period
- Maximal at onset (HB grading should improve and not worsen after that)
- Unilateral
- Isolated CN VII palsy
- No synkinesis or twitching(?)
Recovery progression for Bell’s palsy
Start to improve after a few weeks, with recovery of some/all facial function within 6 months
- Residual muscle weakness may last longer
Management of Bell’s palsy
Conservative
- Physiotherapy (Facial exercises)
Medical
- Steroids (Prednisolone - Benefit is within 72 hours of onset)**
- Analgesia
Prevention/ Tx of Cx
- Eye care (Lubricating eye drops, tape eyelids shut at night, eye gels at night)
- Refer to Eye if exposure keratitis to do tarsorrhaphy
Investigations for Bell’s palsy only conducted for
Only for recurrence/severe Bell’s palsy
Investigations for recurrence/severe Bell’s palsy
MRI
Electroneurography (72 hours to 2 weeks)
Electromyography (>2 weeks)
Pathophysiology of Ramsay hunt syndrome
Reactivation of latent varicella zoster virus residing in geniculate ganglion with subsequent spread of inflammatory process to involve CN7
Clinical features of Ramsay hunt syndrome
- Acute, persistent vertigo
- Unilateral
- Vesicles in ear
- SNHL
- Ipsilateral facial nerve palsy
- Ear pain
- Nystagmus
- History of chicken pox
Management of Ramsay hunt syndrome
- Prednisolone
- Valacyclovir
- Analgesia
- Vestibular suppressants
- Eye care: eye drops, tape eye
Prognosis of Bell’s palsy vs Ramsay hunt syndrome
- Facial palsy usually severe and often doesn’t recover
- Prognosis POORER than in Bell’s palsy
Malignant otitis externa
Rapidly spreading infection by P. aeruginosa or S. aureus to temporal bone, middle ear and inner ear
- Osteomyelitis of bony external ear
Risk factors of malignant otitis external
DM, elderly, immunocompromised
Clinical features malignant otitis externa
- Excessive otalgia OUT OF PROPORTION to ear signs, interferes with sleep and function
- Purulent otorrhea
- Affects CN 7 first –> CN 8 –> CN 9, 10 as it spreads along skull base –> Ipsilateral CN signs/ facial palsy
- Otoscopy: Granulation tissue at bony cartilaginous junction of EAC, intact ear drum
- Does not improve with abx or ear drops
*can DIE if untreated
Investigations for malignant otitis externa
- Swab ear canal +/- Biopsy TRO SqCC
- CT Temporal/ Blood test for inflammatory marker
- MRI scan to determine extent of soft tissue involvement and differentiate b/w inflammation and tumour (NPC)
- Bone scan (Gallium): Taken up by polymorphonuclear leukocytes so areas with active infection i.e. osteomyelitis will be hyperintense (Lights up)
Management of malignant otitis externa
- Admit
- Analgesia
- Intensive pharmacotherapy: IV empirical ciprofloxacin + ceftazidime for at least 6 weeks
- Control predisposing conditions e.g. DM
- Aural toilet (microsuction)
- Surgical debridement of necrotic tissue or bone
Impact of facial nerve palsy
- Dry ears, tearing
- Eating, drooling, drinking
- Difficulty communication
- Change in taste
Types of deformity seen in facial nerve palsy
- Static (at rest)
- Dynamic
- Synkinesis (development of facial movements that were not intended)
Examples of synkinesis
Eye closure when chewing/eating
Lifting of lips when eye is closed/blinks
Grading system for facial nerve palsy
- House-Brackmann Grading*
- Difference between 3 (complete) and 4 (incomplete) is by complete eye closure - Sunnybrook facial grading system
Looks at:
- facial region
- static
- dynamic
- synkinesis
Facial nerve palsy results in
- Loss of symmetry at rest
- Loss of symmetry during movement
- Overcompensation (synkinesis)
Static procedures for resting position
- Brow lift for eyebrow position
- Upper lid blepharoplasty for upper lid ptosis
- Eye tape
- Tarsorrhaphy
- Canthoplasty for excess scleral show
- Slings for blunted nasolabial fold and depressed angle of mouth
Procedures for dynamic movement
2 ends present:
- Close together (<1cm): Stitch
- Further away (>1cm): Find another nerve to join the 2 ends together
Proximal end missing:
- Find another nerve it can join to: Masseteric nerve/ Hypoglossal nerve
- Temporalis, masseter or digastric muscles can take over the function of muscles of facial expression
Treatment of synkinesis
- Neuromuscular retraining (physiotherapy)
- Botox
- Synkinesis surgery
Treatment for flaccid paralysis
- Facial massage
- Stretching exercises
- Assistive movement
- Avoid overactivity of normal side
Complications of facial nerve palsy
EYE
- Eye pain (Exposure keratopathy due to inability close eyes)
- Corneal ulcers
- Red eye
- Bell’s reflex (Upward movement of eye to protect cornea)
- Bogorad’s syndrome: Crocodile tears (Tearing when eating)
MOUTH
- Leakage/ drooling when drinking or eating (Buccinator paralysis)
FACE
- Facial synkinesis (Excessive abnormal and unintended movements)
- Frey’s syndrome (facial sweating and flushing while eating)
Examination for LMN facial nerve palsy
- Cranial nerve PE TRO UMN and neuro PE
INSPECT EAR CLOSELY
- Otoscopy to look at EAC and TM/ middle ear/ vesicular rashes
- Rinne’s and Weber’s tests
CHL –> Middle ear pathology
SNHL –> IAM/CPA/Brain pathology
- Parotid PE for parotid lumps or post-auricular scar suggesting past parotidectomy
- Signs of trauma (temporal bone fracture)
- Grading: House-Brackmann grading
Complications of Ramsay hunt syndrome
Pinna perichondritis
Meningitis
CN9-12 palsies
