Facial Nerve

Anatomy

7th cr n. Mixed Pons & medulla Motor part arises from the facial n. nucleus in the pons Sensory part arises from solitary nucleus via nervus intermedius Secretomotor part arises from the sup. Salivatory nucleus

Motor part

Motor part enters the petrous part of the temporal bone through the internal auditory meatus with the VIII cr.n. then run within fallopian canal crossing the middle ear cavity then it exits from the stylomastoid foramen and emerges through parotid gland to supply the m.m. of facial expressions.

Branches:

B.Outside the canal

Sensory part

Receives taste sensation from ant.2/3 of the tongue Supra tonsillar fossae Small fibers from auricle

Causes of facial n. dysfunction

Bell`s palsy Trauma Infection Tumors Central causes General medical causes

1-Bell`s palsy

Commonest cause Lower motor lesion of unknown cause Possible theories , viral, vascular, or autoimmune ,but none is proven Path: inflammation of the peri-neural sheath can cause swelling of the sheath which may compress the nerve within the bony canal>>FN. paralysis

Clinical features:

Any age & sex 15-45 year Rapid progressive stiffness or numbness of the face lost of forehead wrinkling Incomplete closure of the eye Cannot blow the cheek Lost of the nasal wrinkling Flattening of the nasolabial fold Deviation of the mouth// pulled up toward normal side

Diagnosis

History : Onset ,duration, ass’ symptoms of other disease, trauma, pregnancy, DM, allergy, viral inf….ect,Ex: Severity of the palsy ,ear ex. , full neurological , assessment of the muscles of the face

Investigations:

C.B. F. E.S.R. B.S. E.M.G. E.N.G. Audiological tests /stapedial reflex Radiological test //CT scan & MRI Salivary flow rate

treatment

Medical: steroid (controversial) 1mg/kg/day Antiviral(controversial) Relieve of pain Eye care / oint.& artificial tear Physiotherapy // massage & electrical stimulation

Surgical decompression

Prognosis : - usually good if dx. In 1st . Wk. - rarely residual facial paralysis

2-trauma

Neuropraxia : physiological block Axonotmesis : intact sheath with divided axon>>>mismatch regeneration >> synkinesis Neurotmesis : whole n. is divided>>poor prognosis


3-infection
Herpes zoster oticus I.M.N. O.m. Malignant o.m. Spirochaetal infections

Herpes zoster oticus (Ramsey hunt syndrome)

c/f : - Varicella virus // chickenpox - usually elderly - pain around the ear - vesicles on the auricle & ext. ear - sometime S.N.H.L. - vertigo R, : - pain killer - antiviral // Acyclovir - topical R, for vesicles - short course of high dose of prednisolone * Poor prognosis


4-Tumours : v. schwannoma ,parotid gl. Tumour 5-Central causes : C.V.A, brain abscess , meningitis6- General medical causes: - Sarcoidosis - M S - Guillain – Barre syndrome - D.M.