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Facial NerveDr/ Hytham Nafady
Introduction
Components of the
facial nerve
Branchiomeric motor
Visceral motor
(parasympathetic)
General sensory
Special sensory
(taste fibers)
Origin
Intracranial course
1. Central segment (tegmentum pontis).
2. Cisternal segment (CPA).
3. Canalicular segment (IAC).
4. Labyrinthine segment (Fallopian canal).
5. Geniculate ganglion.
6. Tympanic segment.
7. Stylomastoid segment.
Extracranial course
Branches Intracranial:• Greater superficial petrosal• Nerve to stapedius.• Chorda tympani N.Extracranial:• Posterior auricular.• N to posterior belly of digastric.• N to stylohyoid.• 5 intraparotid terminal branches (temporal,
zygomatic, buccal, mandibular & cervical).
Facial nuclei
• Motor Nuclei:• Facial nerve nuclei lie in reticular formation of
brainstem, ventral to floor (tegmentum) of 4th ventricle.
• Non-Motor Nuclei:– Salivatory– Solitary – Spinal trigeminal.
1. Central segment1. Central segment
Efferent fibers of facial nerve surround nuclei of CN VI & form small mounds on floor of 4th ventricle (facial colliculi) Facial colliculus
2. Cisternal segment2. Cisternal segmentThe cisternal cistern of the facial nerve course through the CP
angle cistern.
Facial N.
AICA
3. Intra-canalicular segment3. Intra-canalicular segment
• The intra-canalicular segment of the facial nerve course within the anterior superior quadrant of the internal auditory canal.
Cn 7
PostAnt
• The superior and inferior divisions of the vestibular nerves are posterior and (keep you from falling back)
Fallopian Canal
• Facial nerve exits IAC via Fallopian canal– Narrowest point
throughout entire course – Felt to be culprit in facial
nerve compression in Bell’s palsy.
Fallopian Canal
4. Labyrinthine segment
• Gives rise to greater superficial petrosal nerve
• Contains taste axons from tongue & somatic fibers
Geniculate ganglion
5. Geniculate ganglion
6. Tympanic segment
• The tympanic segment course posteriorly below the lateral SCC.
• The last parasympathetic fibers leave the nerve via the chorda tympani nerve.
1. canalicular segment.
2. Anterior genu
3. Labyrinthine segment.
7. Stylomastoid segment
Styloid process Stylomastoid foramen
Which parts of the facial nerve that normally enhance?
• Geniculate ganglion.
• Tympanic segment.
• Mastoid segment.
Enhancement of these segments may be asymmetrical.
Enhancement of these segments because of surrounding circum-neural arteriovenous plexus.
Normal enhancement of these segments is due to the presence of circumneural facial arteriovenous
plexus.
Intraparotid segment
Cn 7Cn 7
RMV RMV
Greater superficial petrosal N.
• The GSPN is branch of the facial nerve that innervates the lacrimal gland.
• It contains preganglionic parasympathetic fibers.• It exits the superior surface of the temporal bone
via the facial hiatus.• It passes under the Meckel’s cave to the
foramen lacerum, at which it joins the deep petrosal nerve to form the vidian nerve.
• The vidian nerve passes through the vidian canal to the pterygopalatine fossa.
Clinical Signs Suggesting Site of Facial Nerve Lesion
• Upper facial territory is supplied by bilateral motor cortices
• Lower facial territory is supplied only by contralateral motor cortex
• Therefore, unilateral central lesions spare upper face
• Lesions distal to geniculate ganglion– Mostly motor abnormalities
• Lesions proximal to geniculate ganglion – Motor, gustatory & autonomic abnormalities
Facial nerve pathology
Idiopathic (Bell’s palsy)
Congenital
Traumatic
Inflammatory
Neoplastic
Vascular
Typical Bell’s Palsy
• Incidence – Usually during winter
• Etiology not entirely understood– Possibly viral (Herpes Simplex Virus).
• Viral infection of facial nerve results in demyelination, inflammation & swelling– Traps nerve in narrow confines of fallopian canal
• Diagnosis of exclusion– Made only when clinical & imaging (if necessary)
findings are supportive
Typical Bell’s Palsy
• Usually a clinical diagnosis– Acute onset unilateral (lower or upper) facial
paralysis, posterior auricular pain, decreased tearing, hyperacusis (30%) & disturbances of taste.
• 80-90% recover completely– Over age 60, only 40% recover completely
Imaging in Typical Bell’s Palsy
• Imaging in typical Bell’s palsy is not usually necessary– When necessary, MRI is best
• Normal facial nerve distal to geniculate ganglion may enhance– Facial nerve proximal to geniculate ganglion does not
normally enhance
• In patients with Bell’s palsy, enhancement of facial nerve in fallopian & ICA is typical
Canalicular
Geniculate ganglion
labyrinthine
Mobius syndrome
It is a congenital disorder characterized by
• Bilateral facial diplegia
• Convergent squint
Secondary to 6th & 7th cranial nerve palsiesAssociations:
Other cranial nerve plasies: 5th, 9th, 10th & 12th cranial nerves.
Craniofacial abnormalites.
Chest wall abnormalities.
Upper & lower limb abnormalities.
Normal subject Mobius syndrome
Temporal bone fracture
Longitudinal
Incidence of facial palsy
20 %
Transverse
Incidence of facial palsy
50%
Post-traumatic facial paralysis.
Acute post-traumatic facial paralysis
Delayed post-traumatic facial paralysis
nerve trans-section nerve edema
A fracture line can be seen crossing the facial canal.
Usually there is no fracture line.
On the other hand, a fracture line may be seen to cross the facial nerve canal without any associated nerve dysfunction
Foville syndrome
Millard Gubler syndrome
Hemifacial spasm
At rest During the attack
Vertebro-basilar dolichoectasia
Vascular loop compression
Facial N. schwannoma associated with acquired arachnoid cyst
Intracanalicular facial shwannoma with involvement of the geniculate ganglion.
Geniculate ganglion schwannoma
Geniculate ganglion hemangioma
Geniculate ganglion meningioma
Stylomastoid segment schwannoma
Intra-parotid facial schwannoma
• Target sign.
• Growth toward facial canal, which may be widened
Parotid gland adenocarcinoma with facial nerve perineural spread
Perineural spread along the GSPN
Denervation atrophy of the buccinator muscle
