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Rare occurrence in Le Fort I advancement, presents as
dusky, violaceous mucosal appearance—may also be
compounded by risk factors such as history of radiation,
chemotherapy, smoking, hematologic conditions, diabetes,
trauma, and any other condition that may weaken wound
healing capabilities.
More common in
Large anterior movements
Cases of cleft lip and palate, and/or
Two-piece movements with osseous discontinuity
Blood supply to Le Fort I segment
Interruption of descending palatine a. after osteotomy
Maintained on ascending palatine branch of facial a.
Anterior branch of ascending pharyngeal a., through
mucosal attachments (soft tissue pedicle)
Blindness may also occur—extremely rare
Adverse damage to the optic nerve with osteotomy
extending to the sphenoid bone leading to neuropathy and
blindness
Hypotensive anesthesia—transient ischemia
QUESTIONS YOU WILL BE ASKED
1. Describe the location of the mental and infraorbital nerves
a. Mental n.: between first and second mandibular premolars
b. Infraorbital n.: ~1 cm below rim in midpupillary line
2. Describe the course of the inferior alveolar nerve within the
mandible.
The nerve enters mandibular foramen at lingula on medial
surface of ramus. The nerve enters from medial to lateral cortex
distally. Finally, it curves below mental foramen prior to exiting.
3. Describe the characteristic nasolabial changes following Le Fort
I advancement.
Alar widening, increased tip projection, vertical lip shortening
4. What are the differences between centric occlusion and centric
relation.
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1.
2.
3.
a. Centric occlusion: maximal intercuspation of the teeth in
wear facets
b. Centric relation: normal resting relationship of mandibular
condyle in glenoid fossa
c. CO-CR shift
i. Sacrifice of centric relation in order to obtain occlusion and
increase mandibular projection
ii. Common in class III malocclusion
Recommended Readings
Legan HL, Burstone CJ. Soft tissue cephalometric analysis for orthognathic
surgery. J Oral Surg. 1980;38(10):744‐751.
Panula K, Finne K, Oikarinen K. Incidence of complications and problems
related to orthognathic surgery: a review of 655 patients. J Oral Maxillofac
Surg. 2001;59(10):1128‐1136. discussion 1137.
Proffit WR, Turvey TA, Phillips C. Orthognathic surgery: a hierarchy of stability.
Int J Adult Orthodon Orthognath Surg. 1996;11(3):191‐204.
*
Denotes common in-service examination topics.
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19
Facial Palsy
Alisa Yamasaki
OVERVIEW
FACIAL NERVE ANATOMY AND
FUNCTION
The Facial Nerve Contains Motor and Sensory Nerve Fibers
Special visceral efferent
Motor control of muscles derived from the second
branchial arch
Includes muscles of facial expression, posterior belly of
digastric, stylohyoid, intrinsic muscles of auricle
(posterior auricular nerve), and stapedius (nerve to
stapedius)
General visceral efferent
Provides preganglionic parasympathetic secretomotor
innervation
Sublingual and submandibular glands (chorda tympani)
Lacrimal, nasal, and palatine glands (greater superficial
petrosal nerve)
Special visceral sensory afferent
Transmits taste from anterior 2/3 of tongue and
hard/soft palate (chorda tympani)
General somatic sensory afferent
Transmits sensation from external auditory meatus,
auricle, and retroauricular area (posterior auricular
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nerve)
General visceral afferent
Transmits feelings of pain from nasal cavity, sinuses,
and soft palate (greater superficial petrosal nerve)
Very small component of facial nerve function
Intratemporal Facial Nerve
Intracranial facial nerve and nervus intermedius travel in the
cerebellopontine angle.
Enters the temporal bone with the vestibulocochlear nerve
via the internal auditory canal and exits at the stylomastoid
foramen.
Divided into the meatal (canalicular), labyrinthine, tympanic
(horizontal), and mastoid (vertical) segments.
Labyrinthine segment is the narrowest and shortest
segment, most susceptible to injury (eg, temporal bone
trauma, infection) and vascular compromise.
Extratemporal Facial Nerve
Begins at the stylomastoid foramen and branches into the
posterior auricular nerve, stylohyoid branch, and digastric
branch prior to innervating the facial mimetic muscles (Fig.
19-1).
*Three anatomic landmarks are commonly used to
identify the main trunk of the facial nerve as it exits the
stylomastoid foramen.
Tragal pointer: located 1 cm anterior, inferior, and
deep to the tragal cartilage.
Tympanomastoid suture: located 6-8 mm deep to the
inferior edge of the suture line.
Posterior digastric muscle attachment to the
digastric ridge: delineates depth of facial nerve.
A small branch off the occipital artery is often
encountered just lateral to the nerve; thus, brisk
bleeding is usually an indicator that the nerve is
nearby.
In children, the facial nerve runs more lateral and
superficial.
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Main trunk divides into upper and lower divisions at the
pes anserinus and divides the parotid gland into
superficial and deep lobes.
Upper division: temporal, zygomatic, and buccal
branches
Lower division: buccal, marginal mandibular, and
cervical branches
Anatomic Pearls for Extratemporal Facial Nerve Branches
Temporal (frontal) branch
*Lies superficial to the superficial layer of the deep
temporal fascia and deep to the temporoparietal
fascia that is continuous with SMAS
*Pitanguy’s line: line drawn from 0.5 cm below the
tragus to 1.5 cm above the lateral brow,
approximating the course of the frontal branch
Especially prone to symptomatic injury due to its
location and lack of redundancy (ie, it does not
arborize)
Zygomatic branch
Crosses the zygomatic arch along the middle 1/3
Zuker point: midpoint of line drawn from helical root to
oral commissure, approximating zygomatic/buccal
branch that innervates the zygomaticus major
Buccal branch
Lies deep to the SMAS where it arborizes and forms
extensive interconnections
*Most common facial nerve injury during
rhytidectomy, but rarely symptomatic due to its
redundancy
Marginal mandibular branch
Lies deep to the platysma muscle.
*Runs along inferior border of the mandible (80%)
or 1-2 cm below it (20%) prior to its intersection
with the facial vessels.
After crossing the facial vessels, it remains above the
border of the mandible.
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Similar to the temporal branch, it is especially prone to
symptomatic injury due to its lack of redundancy.
Cervical branch
Located ~1 cm below the half-way point of a line
between the mentum and mastoid process (ie, below
mandibular angle)
Muscles of Facial Expression (Fig. 19-1 and Table 19-1)
TABLE 19-1 Muscles of Facial Expression
Four layers of facial musculature, from superficial to deep:
Depressor anguli oris, zygomaticus minor, orbicularis
oculi
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Depressor labii inferioris, risorius, platysma,
zygomaticus major, levator labii superioris alaeque nasi
Orbicularis oris, levator labii superioris
Mentalis, levator anguli oris, buccinator
*All muscles are innervated on their deep surface
except for the buccinator, levator anguli oris, and
mentalis
ETIOLOGIES OF FACIAL PALSY
Facial paralysis can result from a lesion anywhere along the
length of the facial nerve
Intracranial etiologies: compressive masses tend to have
an insidious onset, while acute vascular obstruction can
cause sudden-onset facial paralysis
Neoplastic: cerebellopontine tumor (eg, vestibular
schwannoma, meningioma), facial nerve schwannoma
Traumatic: penetrating trauma, shear injury
Infectious: encephalitis, meningitis, cerebral abscess
Vascular: aneurysm, stroke, vasculitis, intracerebral
hemorrhage
Neurodegenerative: amyotrophic lateral sclerosis,
multiple sclerosis
Iatrogenic: tumor extirpation
Congenital: Möbius syndrome, Goldenhar syndrome,
hemifacial microsomia
*Möbius syndrome is the most common cause
of bilateral facial palsy
Can also involve other cranial nerves (eg,
abducens) as well as chest wall and limb
abnormalities
*Patients typically present with a motionless
face and inability to abduct the eyes
Intratemporal etiologies: injury often caused by swelling
and/or compression of the nerve within the facial canal
Neoplastic: cholesteatoma, facial nerve schwannoma
Traumatic: temporal bone fracture
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Classified as either longitudinal (80%; parallel to
long axis of petrous pyramid) or transverse (20%);
or otic capsule sparing vs otic capsule involving
Higher risk of facial paralysis with transverse and
otic capsule-involving fractures
Infectious: otitis media/mastoiditis, Lyme disease,
HSV, HIV, mononucleosis, syphilis, Ramsay-Hunt
syndrome (“herpes zoster oticus”)
Ramsay-Hunt is characterized by unilateral facial
paralysis, otalgia, and a painful vesicular rash in
the external auditory canal.
Oral corticosteroids and antivirals
recommended within 72 hours of onset.
Vascular: cavernous hemangioma
Iatrogenic: Tumor extirpation, otologic surgery
(eg, mastoidectomy, tympanoplasty, external
auditory canal exostosis removal)
Systemic: Guillain-Barré, sarcoidosis, diabetes,
Melkersson-Rosenthal syndrome (MRS)
MRS is characterized by recurrent facial
paralysis, painless orofacial
edema/granulomatous inflammation of the lips
(granulomatous cheilitis), and a fissured
tongue (lingua plicata)
Associated with uveitis, diverticulitis,
ulcerative colitis, and Crohn disease
Treat with oral
corticosteroids/immunosuppressants
Toxins: lead poisoning, carbon monoxide
Idiopathic: Bell palsy
*Most common cause of unilateral facial
paralysis in adults.
Diagnosis of exclusion thought to involve a
viral-induced inflammatory process leading to
nerve edema and compression.
Defined by acute onset <72 hours, treat with
oral corticosteroids and antivirals within 72
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hours of onset.
Higher incidence in pregnant and diabetic
patients.
Hyperacusis, age > 60, diabetes mellitus,
hypertension, and severe radicular pain are
poor prognostic factors.
Most patients (85%) experience some
recovery within 3 weeks and complete
recovery by 3-4 months.
Facial nerve decompression is controversial.
Extratemporal etiologies
Neoplastic: parotid tumor, metastatic skin cancer,
facial nerve schwannoma
Traumatic: penetrating trauma, birth trauma
*Exploration must be performed <72 hours of
injury (prior to Wallerian degeneration) so that
distal ends can be identified by electrical
stimulation
*General “rule of thumb” is that facial nerve
exploration is not warranted for distal injury
(ie, medial to the lateral canthus)
Birth trauma typically involves neuropraxia that is
managed conservatively
Infectious: parotitis
Iatrogenic: tumor extirpation, facial surgery (eg,
parotidectomy), TMJ surgery
Congenital: congenital unilateral lower lip paralysis
(CULLP)
Caused by hypoplasia or absence of the lower lip
depressors
Typically presents with deviation of the lower lip
toward the unaffected side (eg, when crying)
Bilateral facial paralysis is not as common as unilateral facial
paralysis but causes include Möbius syndrome, Lyme disease,
toxins, and systemic infection (eg, HIV)
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Figure 19-1 Facial nerve anatomy and
facial musculature. (From Dalley AF II, Agur
AM, eds. Moore’s Clinically Oriented
Anatomy. 9th ed. Wolters Kluwer; 2023.
Figure 10.11B.)
EVALUATION OF FACIAL PALSY
Assess Facial Nerve Prognosis and Muscle Viability
Onset and severity of symptoms: gradual onset (eg,
neoplastic, neurodegenerative, systemic) vs acute onset
(eg, traumatic, vascular, infectious, iatrogenic, idiopathic),
partial vs complete palsy, facial zones involved
Determine potential etiologies (see Etiologies of facial
palsy section)
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