الفهرس 
EmbryologyOnly 14 pages are availabe for public view
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Abstract
Understanding of the facial nerve embryology allows otologic surgery to be planned with reasonable accuracy and carried out safely and expeditiously.
Development of the facial nerve and its related musculature is well established by the end of the third month of gestation. The anatomy of the facial nerve can be divided into two distinct pathways: central and peripheral. The central pathways include the supranuclear tracts and the facial nucleus and brainstem components. The peripheral nerve comprises that in the internal auditory canal , fallopian canal and its terminal branches.
A typical motor neuron consists of a cell body, a long fibrous axon covered with myelin, and terminal branches.
The axonal membrane is polarized at rest (positive outside, negative inside).The polarity is reversed during an action potential (impulse).
When injury is placed on a nerve, the transmission of nerve impulses blocked.
Facial nerve paralysis can stem from a variety of causes and may involve the supranuclear tract to the brainstem (intracranial course), the intratemporal segments, or the extratemporal portions. The disorder may even involve multiple segments of the nerve. The paralysis can be idiopathic or caused by trauma, systemic infection, acute or chronic otitis media, metabolic disorders, toxins, vasculitides, neurologic disorders, neoplasms (both benign and malignant), radiation therapy, and numerous other causes.
A thorough history and physical examination is crucial to the evaluation of any patient with facial nerve disorder. Every effort should be made to determine the etiology. Factors that are assessed include date of onset, rapidity of progression and duration of symptoms, risk factors, co-morbidities and associated symptoms are equally important.
Regardless of what must be done to the facial nerve, the basic exposure in the temporal bone involves opening the fallopian canal without disruption of nearby neurovascular, intracranial, or inner ear structures. Depending on the site of the lesion and preoperative hearing, the nerve may be exposed via the MCF, retrosigmoid, translabyrinthine, and/or transmastoid approaches.
There are two general surgical methods for rehabilitating a paralyzed face, dynamic and static.
A – Static procedures
1 - Care of the eye
a-) Gold weight
b-)Tarsorrhaphy
c-) Lateral tarsal strip procedure
2 - Brow ptosis correction (Brow lifting)
3 - External nasal valve repair
4 - Static facial slings
5 - Nasolabial fold modification
6 - Lip and cheek reconstruction
B – dynamic procedures
1 – Decompression
2 - Nerve repair procedures
a-) Primary neurroraphy
b-) Facial Nerve Rerouting
I - Anterior facial nerve rerouting
i - the short rerouting technique
ii - the long rerouting technique
II - Posterior facial nerve rerouting
c-) Cable grafting
I - Great auricular nerve
II - Sural nerve
3 - Nerve Substitution procedures
a-) hypoglossal nerve substitution
I - End-to-end hypoglossal-facial anastomosis
II - Hemi-end-to-end hypoglossal-facial anastomosis
III - Side-to-end hypoglossal-facial anastomosis
IV - Hypoglossal-facial jump graft
b-) cross-facial nerve grafting
c-) Other reinnervation (substitution) techniques
4 - nerve growth factors and microtubule(conduits)
5 - Muscle transfer techniques
a-) Regional muscle transfer(Muscle transposition)
I - Temporalis muscle transposition
II - Other regional muscle transfers
i - Masseter muscle transfer
ii - Digastric muscle transfer
b-) Free muscle transfer(Free muscle flaps)
6 - Application of stem cells in tissue-engineered artificial nerve
C – Other procedures (Non-surgical)
Conclusion :
The main achievement of patients are the recovery of full facial symmetry at rest and complete eye closure in all cases. All of them considere that the gain is substantial and that the quality of their social life is enhanced.
Finally, to make an informed decision for surgery, the patient must understand what is realistically achievable in his or her case. The surgeon needs to discuss with the patient possible results of facial reanimation surgery.
In conclusion, all ENT specialists must be familiar with facial nerve repair procedures, above all those who work in otoneurosurgery. When carried out in time, they can reestablish facial symmetry at rest and eyelid closure in the vast majority of patients.
It is hoped that further understanding of neurotropic growth factors for motor neurons will provide a new basis to develop treatments for facial nerve injuries.