Facial Nerve Palsy

Anatomy Facial nerve is a mixed nerve, having a motor root and a sensory root Motor root supplies all the mimetic muscles of the face which develop from the 2nd brachial arch 2

Anatomy Sensory root “nerve of Wrisberg” carries taste fibers from the anterior 2/3 of the tongue and general sensation from the concha and retroauricular skin Also it carries secretomotor fibers to the lacrimal, submandibular and sublingual glands as well as those in the nose and palate 3

Anatomy: Parts Intracranial part Intratemporal part Extracranial part 4

Course of the Facial Nerve Intracranial Arises at the pontomedullary junction and courses with CNVIII to the internal acoustic meatus 12mm

Course of the Facial Nerve Intratemporal Meatal Labyrinthe segment Tympanic segment Mastoid segment

Course of the Facial Nerve Extracranial From stylomastoid foramen to pesanserinus

Anatomy: Branches Greater superficial petrosal nerve Nerve to stapedius Chorda tympani Comunicating branch Posterior auricular nerve Muscular branches Peripheral branches: “Pes anserinus” 8

Presentation Functional and cosmetic problems Upper lid fails to drop down and close Lower lid loses tone and sags downward May evert leading to ectropion Produces lagophthalmos and consequent corneal exposure. 9

Presentation Interruption of the tear film Leads to drying of cornea Ocular discomfort Corneal ulcers Infection Perforation 10

Presentation Upper motor neurone (UMN) can wrinkle their forehead (unless bilateral lesion) Lower motor neurone (LMN) can't wrinkle their forehead

House-Brackmann Facial Nerve Grading Scale I. Normal II. Mild dysfunction (slight weakness noticeable on close inspection) III. Moderate dysfunction (obvious weakness, but not distinguishing differences between the two sides of the face) IV. Moderately severe dysfunction (obvious weakness and disfigurement) V. Only barely perceptive motor function VI. Complete paralysis

Diagnosis History Presentation Hearing test Vestibular function MRI / CT Topognostic - Where is the lesion? Qualitative -Degree of the lesion

Topodiagnostic Diagnosis Schirmer’s tear test Stapedius reflex Taste test Submandibular salivary flow test 14

Topodiagnostic Diagnosis

Qualitative Diagnosis Nerve Excitability Test: NET Maximum stimulation Test: MST Electroneurography: ENoG Electromyography: EMG 16

Bell’s Palsy 60-70% cases Pathophysiology – Impaired “axoplasmic” flow from edema of facial nerve within fallopian canal Rapid onset and evolution < 48 hours May be associated with acute neuropathies of cranial nerves V- X Pain or numbness affecting ear, mid-face, tongue and taste disturbances Recurrences are more likely (2.5x) in patients with family history, immunodeficiency or diabetes

Pathophysiology Main cause of Bell's palsy is latent herpes viruses (herpes simplex virus type 1 and herpes zoster virus), which are reactivated from cranial nerve ganglia. Polymerase chain reaction techniques have isolated herpes virus DNA from the facial nerve during acute palsy. 18

Treatment Oral antivirals - Acyclovir Corticosteroid Eye protection - lacrilube Follow progression with serial exams Facial nerve decompression Progression to > 90% degeneration on ENOG Performed before irreversible injury to the endoneurial tubules occurs (two weeks), will allow for axonal regeneration to occur

Herpes Zoster Oticus (Ramsay Hunt syndrome)

Herpes Zoster Oticus (Ramsay Hunt syndrome) 10-15% of acute facial palsy cases Lesions may involve the external ear, the skin of EAC or soft palate Associated symptoms – hearing loss, dysacusis and vertigo Additional involvement of CN V, IX and X and cervical branches 2, 3 and 4 Pathogenesis – Neural injury due to edema at point between the meatal foramen and the geniculate fossa in the labyrinthe segment

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