Approach
to the patient with…
Facial
Weakness
Facial
weakness is usually due to dysfunction of the facial nerve (CN VII) or its
supranuclear pathways, leading to paresis of facial movements on one side
- broadly
classified into lesions of the nerve itself (lower motor neuron) vs
lesions of the corticobulbar pathways that innervate and send signals to this
nerve (upper motor neuron)
-
differentiated by involvement of the upper face on the affected side; which is
spared (esp frontalis) in UMN lesions while there is equivalent weakness of eye
closure and eyebrow raising in LMN lesions
Anatomy:
The
facial nerve (CN VII) is a mixed motor and sensory nerve
- the
motor division arises from the motor nucleus in the caudal pontine tegmentum
medial to the nucleus of CN V and anterolateral to CN VI nucleus
- the nerve
courses medially and posteriorly around the CN VI nucleus to create the facial
colliculus and then ventrally to exit in the cerebellopontine angle close
to the fifth, sixth and eight CNs
- its
supranuclear control is via corticobulbar fibres originating in the lower 1/3
of the precentral gyrus ("motor strip") which traverse the corona
radiata, genu of the internal capsule and medial cerebral peduncle to synapse
in the pons
-
majority of the fibres decussate but there is bilateral innervation to the dorsal
portion (which supplies muscles of the upper face, esp frontalis); so spared
relatively in UMN lesions
- this
pathway is for voluntary facial movements while mimetic facial movements
(ie. involuntary, eg smiling spontaneously) are mediated by pathways traversing
striatum or globus pallidus (and especially involved if lesions of right
hemisphere)
- nervus
intermedius (of Wisberg) supplies the preganglionic parasympathetic fibres
to the submaxillary ganglion (innervating the submandibular and sublingual
salivary glands) and to pterygopalantine / sphenopalantine ganglia (to
lacrimal, palatal and nasal glands)
- sensory
input comes from geniculate ganglion (taste from anterior 2/3 of tongue
and mucosa of pharynx, nose, palate, and external auditory meatus incl. lateral
pinna)
-
parasympathetic fibres originate in superior salivary nucleus (in pontine
tegmentum) and lacrimation from lacrimal nucleus
- gustatory
afferents terminate in nucleus tractus solitarius (medulla) while other
sensory fibres end in spinal nucleus of trigeminal nerve
- its
peripheral course is together with CN VIII entering internal auditory meatus to
facial canal in petrous bone where it reaches the geniculate ganglion
- chorda
tympani (as well as nerve to stapedius) arises in the mastoid (vertical)
segment in middle ear; this supplies the submaxillary ganglion and afferents
from taste
- exits
facial canal through stylomastoid foramen giving off branches to various
muscles
- pierces
the parotid gland and supplies more muscles
History:
Onset:
- was
this acute (as with stroke or Bell's palsy) and static or was it insidious and
progressive (as with mass lesions or leptomeningeal inflammations or
malignancies) ?
- how
first noticed (by others, self in mirror, trouble closing eye - shampoo gets in
eye while showering esp LMN or food accumulating in corner of mouth or drooling
out of one side)
Pain:
- swelling of the nerve (eg Bell's Palsy / inflammatory) commonly leads to
entrapment near stylomastoid foramen, causing localized pain anterior to tragus
of ear (in 50% of Bell's palsy)
- otalgia
or pain behind ear may occur due to involvement of the geniculate ganglion
- severe
pain seen with Ramsay-Hunt syndrome (geniculate neuralgia)
Hyperacusis:
-
subjective feeling that noises sound louder in ipsilateral ear (due to weakness
of stapedius which dampens sound vibrations); esp for low tones; seen in 14% of
Bell's palsy
- only
seen in peripheral localization with lesion proximal to stylomastoid foramen
(as nerve to stapedius leaves while CN VII still in facial canal)
Dysgeusis:
-
alteration in taste implies lesion proximal to point where chorda tympani joins
facial nerve
Lacrimation:
- despite
potential impairment of lacrimation (if proximal lesion) still often see
increased tearing ipsilaterally, due to irritation from inability to close eye
and dysfunction of tear duct
- few
complain of dry eyes
Examination:
Of facial
weakness itself:
1. Motor:
- inspect
the face at rest and with voluntary (and mimetic) movements
- examine
symmetry of eye blinking and speech motion (subtle lesions may only lead to
asymmetry of blink rate !)
- ask to
raise eyebrows (frontalis), close eyes (orbicularis oculi), show teeth
(orbicularis oris), blow out cheeks (buccinator), scrunch up nose (nasalis) and
retract chin (platysma)
NB: with
true eye closure weakness, when try to pry them open, should see globe rotated
upward (Bell's phenomenon) due to contraction of superior rectus (absent
in 10% of normals)
-
determine whether peripheral (LMN) or central (UMN) lesion; in former see no
furrows on affected forehead and ipsilateral eye open wider (unable to close)
- look
for signs of hemifacial spasm (contraction of facial muscles on one side
due to nerve irritation) which can falsely mimic contralateral facial weakness
2.
Sensory:
- see if
associated loss of taste on anterior two-thirds of tongue
- test
for sweet and salty on one half vs. unaffected side
- only
involved with peripheral lesions as supranuclear or nuclear motor lesions do
not affect this sensory function
3.
Reflexes:
- corneal
reflex may be reduced ipsilaterally (if LMN lesion) due to weak efferent loop
(while consensual blinking on unaffected side remains intact)
Associated
brainstem abnormalities:
- to
localize a nuclear (LMN) lesion of CN VII should seek other nearby brainstem
problems
- usually
affects CN VI (abduction, lateral rectus paresis) or conjugate gaze (PPRF)
-
corticospinal tract may be involved in basis pontis (as nerve exits) with CL
hemiparesis
-
occasionally trigeminal nerve and spinothalamic tract (crossed sensory loss)
Cerebellopontine
Angle abnormalities:
- loss of
taste and hyperaccusis will be present
-
associated with ipsilateral hearing loss, tinnitus +/- vertigo
- if
extend to adjacent pons or cerebellum, may see gaze paresis, ataxia, sensory
loss
- similar
abnormality with temporal bone fracture involving facial nerve in bone,
including loss of hearing and impaired lacrimation
Look for
vesicles in the ear canal or tympanic membrane as well as palate
- seen in
varicella-zoster reactivation involving the seventh CN (Ramsay-Hunt)
-
commonly also see vestibulocochlear dysfunction with hearing loss, vertigo
Differential
Diagnosis of Facial Weakness:
1. UMN
Pattern (supranuclear) - requires brain
imaging with CT or MRI
- Infarct
or hemorrhage along corticobulbar pathway (cortical or subcortical)
- Tumor
or other mass lesion (incl. focal infections)
- Demyelinating
or other inflammatory lesions
2.
Nuclear lesions:
- with
associated brainstem abnormalities
-
ischemic or hemorrhagic lesions (incl cavernoma), demyelinating focus or
pontine gliom
3. LMN
Pattern (peripheral):
a. Bell's
palsy; idiopathic (see below for complete differential)
b.
Traumatic
c.
Infectious (esp VZV, HIV, Lyme disease, basal meningitis)
d.
Inflammatory (esp sarcoidosis)
e.
Neoplastic (esp schwannoma or CPA meningioma)
f.
Metabolic (esp diabetes mellitus, pregnancy)
Bell's
Palsy:
Acute
unilateral mononsymptomatic and idiopathic peripheral CN VII palsy
Epidemiology:
- the
most common peripheral disorder of CN VII (accounts for 2/3 of LMN VII palsies)
- occurs
in 23 per 100,000 persons per year
- affects
men & women equally, all ages, and all year round (peak at ages 15-45 yrs)
- each
side affected with same frequency
- lesion
most commonly proximal to geniculate ganglion and role of HSV-1 viral infection
(or post-viral) implicated; alternatively role of ischemia and microinfarction
of the nerve (eg DM)
History:
- usually
acute onset over a day or so of unilateral facial weakness
- LMN
pattern so problems with closing eyes, eating, drooling
- may be
preceded for 1-2 days by pain around the ear
- ask
about dysgeusis (alteration in taste) or hyperaccusis which do not always occur
and localize the lesion proximal to where chorda tympani and nerve to stapedius
originate
- any
prior history of facial palsy (is this recurrent or episodic)
R/O other
problems:
- no
symptoms of brainstem dysfunction such as diplopia / gaze palsy, sensory loss
in face, or hearing loss / vertigo
- no
severe pain in or around ear to suggest Herpes Zoster Oticus
(Ramsay-Hunt)
Examination:
- LMN
pattern of facial weakness involving all muscles on that side
- no objective
sensory loss (though face may feel "heavy") or other neurological
abnormalities (no pronator drift or other pyramidal deficits on same side to
suggest an UMN pattern of corticospinal / corticobulbar abnormality)
- look at
the external ear and palate for vesicles suggesting VZV reactivation
(Ramsay-Hunt)
Differential
Diagnosis: see
above for full list
LMN
Facial weakness:
-
Infections (VZV, HIV, Lyme disease, Leprosy, Syphilis, meningitis incl. TB,
Parvovirus B19)
- Parotid
swelling (incl. mononucleosis, mumps, mass lesions)
-
Inflammatory diseases incl. sarcoidosis, Wegener's granulomatosis, giant cell arteritis, polyarteritis nodosa and
Behcet's disease; also Guillain-Barre syndrome
-
Leptomeningeal processes incl. meningitis
(see above), carcinomatosis
-
Neoplasms compressing the nerve incl. cholesteatoma, facial nerve schwannoma,
meningioma or vestibular schwannoma at CPA, glomus jugulare tumor, carcinoma
(or other tumors) in ear, parotid tumors
-
Traumatic injuries to the facial nerve incl. temporal bone fractures, birth
trauma / forceps delivery, or post-operative (ear surgery)
-
Metabolic dysfuntion incl. diabetes mellitus, hypothyroidism, uremia, porphyria
- Drug
reactions incl. Stevens-Johnson, isoniazid, lidocaine
-
Congenital defects of CN VII incl. Mobius syndrome (abducens palsy) or familial
-
Melkersson-Rosenthal syndrome with recurrent facial palsy associated with
labial edema and plications of tongue
Investigations:
- none
required for typical case without other neurological features or concerning
history
- imaging
of the facial nerve course with CT scan or MRI if suspect mass lesion
compressing or trauma history (assess for basal skull fracture)
NB: in
Bell's palsy may see enhancement of distal intracanalicular and labyrinthine
segments of facial nerve, geniculate ganglion and other portions (swelling of
the nerve is normal)
- ESR,
glucose, VDRL, HIV and vasculitis testing in appropriate situations
- CSF analysis if suspect
leptomeningeal disease (for cytology, cells, ACE level, VDRL)
Electrophysiology
Help with
prognostication and mainly done if no prompt resolution of facial weakness when
peripheral lesion of the nerve suspected clinically
1. Blink
response (direct R1, indirect R2)
- normal
(unusual with significant facial palsy), delayed, or absent
2. Direct
response from nasalis (equivalent to
facial CMAP)
-
comparison of amplitudes on affected vs unaffected side
3.
Transcranial magentic stimulation:
-
response may be absent early on due to edema, while still reversible
- absent
not necessarily poor prognosis but presence of response means likely to have
good recovery (esp if < 4d from onset)
Initial
testing may be done within 10 days of onset
- full recovery
if blink response present and direct response > 25% of normal side
- poor
recovery if direct response < 25% (in this case, blink R1 usually absent)
If blink
response absent at initial testing but present at 1 month (with DR > 25%)
then usually still good recovery
Natural
History:
-
recovery complete or with only mild residual weakness in over 90%
- 5-10%
have mod-severe residual weakness (usually only if complete severe weakness at
initial presentation)
- 80%
begin to recover within 3 weeks (demyelinating lesion) while 15% start their
recovery only by 3-5 months
- almost
all recovery has occurred by 6 months, and little more expected after 1 year
- poor
prognosis if older, complete initial weakness (if partial then 94% make
complete recovery), if not start to recover within 3 weeks, presence of
post-auricular pain and associated conditions (diabetes, pregnancy, VZV
infection); also if taste impairment
- see
also electrophysiologic parameters above
- risk of
recurrence if low for Bell's palsy
- if recurrent
then consider inflammatory conditions, myasthenia gravis or lesions at skull
base (incl. meningitis, sarcoidosis or tumors - lymphoma)
-
sequelae include residual weakness in 10-15%, contractures in 17%, and aberrant
regeneration with synkinesis in 16% (incl. crocodile tears, tear when
eat in 2%)
Treatment:
- careful
eye care including daytime drops to lubricate (else dry eyes) and nightime
lubricanting ointment lacrilube) and taping eye shut (if cannot close fully) to
proect from corneal abrasions and ulcers
- if seen
within first few days and significant weakness, then consider prednisone
1 mg/kg daily for 10 days then tapered off rapidly
(shown to
reduce time to full recovery but not affect ultimate degree of recovery at 1
year)
-
optional (with weak evidence) to use acyclovir orally if seen early, as HSV
infection is commonly implicated in Bell's palsy (but not often proven)
-
decompressive surgery has been advocated but complications include hearing loss
(permanent) in 1-15% and no definite benefit over medical management proven
- no
point decompressing > 14 days from onset when severe damage and degeneration
done but role of reconstructive facial nerve surgery later for complete
transection possible
Bilateral
Facial Weakness:
UMN
Pattern (or
non-neurogenic)
-
Myopathies (incl. FSH, myotonic dystrophy, OPMD)
-
Bilateral strokes (usually with pseudobulbar palsy)
LMN
Pattern: Facial
Diplegia
-
unusual, accounting for less than 1% of facial weakness cases
caused
by:
1.
Congenital:
- Mobius
syndrome, Poland's anomaly (pectoralis hypoplasia with ipsilateral breast and
upper limb abnormalities), maternal thalidomide use
2.
Granulomatous / Connective Tissue diseases:
-
sarcoidosis (incl. uveoparotid fever), vasculitis (Sjogren's, SLE, GCA, Wegener's, PAN)
3.
Infectious:
-
meningitis (incl. TB, cryptococcus), encephalitis, Lyme disease, HIV, leprosy,
VZV, CMV, botulism, tetanus, diphtheria
4.
Neoplasms:
- pontine
glioma, extra-axial lesions incl. epidermoid, cholesteatoma, ependymoma
bilaterally or menigeal (leukemia, lymphoma)
5.
Traumatic
7.
Multiple idiopathic cranial nerve palsies
8.
Bulbospinal neuronopathies: incl. brainstem encephalitis, amyloidosis,
Stevens-Johnson syndrome, diabetes mellitus, multiple sclerosis, intracranial
hypertension, porphyria, osteopetrosis, ethylene glycol toxicity, HNPP,
Tangier's disease
References:
Gilden
DH. Bell's palsy. N Engl J Med 2004; 351: 1323-31.
Grogan
PM, Gronseth GS. Practice parameter:
steroids, acyclovir, and surgery for Bell's palsy (an evidence-based
review). Neurology 2001; 56:
830-6.
Reviewed by: pending
review
Neurological
Medicine Pocketbook
© 2003-2004
UWO Neurology Residents
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