Facial Paralysis
Discuss etiology and management of injury of facial nerve.
Answer. Injuries of facial nerve causes facial palsy or Bell’s palsy.
Etiology Of Facial Paralysis
- Congenital: Mobius syndrome (Uncommon and poorly understood)
- Traumatic:
- Birth injury
- Iatrogenic injury at the time of surgeries, e.g. surgery for parotid gland surgery etc.
- Blunt or penetrating trauma to nerve.
- Fracture of the temporal bone can lead to facial nerve injury.
- Infections
- Virally mediated diseases, i.e. herpes zoster, mumps,coxsackie virus, and mononucleosis.
- Bacterial infections, i.e. sequelae to otitis media, Lyme disease, mastoiditis.
- Inflammatory conditions: Sarcoidosis
- Neoplastic: Tumors of the parotid gland (typically malignant tumors)
- Facial nerve schwannomas
- Acoustic neuromas
- Neoplasms of the brain such as brainstem tumors.
- Idiopathic:
- Bell`s palsy is most common type of facial paralysis.
- It occurs due to virally induced inflammation of the nerve resulting in compromise of the function of nerve, swelling and vascular supply to the nerve.
- Melkersson—Rosenthal syndrome
- Myasthenia gravis.
Read And Learn More: Neurological and Facial Disorders: Causes, Diagnosis, and Treatment Strategies
“Facial Nerve Injury After Ear Surgery”
Management Of Facial Paralysis
Facial nerve repair can be done by following surgical methods,i.e.
- Direct repair
- Cable nerve grafting
- Nerve substitution techniques.
“Mri Vs Ct Scan For Facial Nerve Injury”
Direct repair Of Facial Paralysis
Preoperative Details
- Direct repair of the facial nerve is the best method to rehabilitate the paralyzed face.
By this method,there are chances of restoring spontaneous, emotional expression to the face. - Direct repair is indicated in cases where the length of nerve is adequate and reapproximation of the nerve is possible without tension along the nerve.
- It involves restoring the continuity of both ends of the nerve directly by using sutures.
- For the successful repair of nerve, it is mandatory that functional motor unit be available to receive the innervations, i.e. facial musculature should not have undergone excessive atrophy and there should be no firosis at the motor end plate which prevent reinnervation.
“Role Of Infections In Facial Nerve Paralysis”
Technique of Direct Repair
- Parotidectomy incision is given and the nerve is exposed.
Identify the nerve and its branches.
If the intratemporal portion of the nerve is injured, this area is exposed with the help of a mastoidectomy. - As identification is over, the nerve is followed distally as required.
- Handle the nerve as traumatically as possible.
Surgery should be performed by using a surgical microscope.
This allows precise alignment of the nerve ends. - 2 to 3 sutures should be placed by using 8-0 to l0-0 fie monofiament sutures.
Sutures are usually placed through the epineurium. - Perineurial, endoneurial and interfascicular suturing should also be done.
- Most important relationship is the size match of endoneurial surfaces. This must be inspected with magnification, and if a mismatch is seen, then one end may be trimmed in a beveled fashion to obtain a bettr surface area.
Cable nerve Grafting
If sufficient length is not present to approximate the nerve primarily, cable grafting is done.
Patient must be informed about the operation of the donor site.
Commonly used nerves are greater auricular nerve, sural nerve, lateral femoral cutaneous nerve, etc.
Cable nerve Grafting Technique
- Great auricular nerve is located by drawing a line between angle of jaw and mastoid tip.
Bisect this line at a right angle by great auricular nerve as it passes around the posterior border of the sternocleidomastoid muscle just behind the external jugular vein. - Sural nerve may be located between lateral malleolus and Achilles tendon.
It lies deep or posterior to the saphenous vein.
Sural nerve then runs superiorly up to back of lower leg in a subcutaneous plane until it descends between the two heads of the gastrocnemius toward the popliteal fossa and its origin of the tibial nerve.
Sural nerve can be harvested either by giving a single long incision from the ankle to popliteal fossa (depending on the length of nerve required) or a series of shorter transverse incisions.
The nerve may be dissected under direct vision with the single incision, or by employing a fascia stripper and making the stepwise incisions. Nerve grafting should be done same as for primary repair.
In cable grafting, it may be helpful to obtain enough nerve graft length to allow the graft to have some redundancy between the ends of facial nerve.
This provides a C or S shape and ensures tension-free coaptation. - Graft should lie in healthy and vascularized recipient site which is free of scar tissue.
- Epineurium should be intact and 10-0 sutures may be used to repair the nerve without tension.
A soft silicone tube can be used which surround the anastomotic site to prevent in growth of scar tissue inside the surgical site and also to keep cut axons approximated.
“Difference Between Bell’S Palsy And Facial Nerve Injury”
Nerve Substitution Techniques
There are two types of nerve substitution techniques:
1. Hypoglossal facial anastomosis
2. Cross-face grafting
Hypoglossal Facial nerve anastomosis
It is the most standard procedure to reanimate the face when proximal end of the facial nerve is not present or has undergone degeneration and the peripheral aspect of nerve is still viable.
This procedure can be done as a primary procedure, i.e it can be done along with the surgical procedure that lead to the sacrifice of the facial nerve or as a secondary procedure, i.e. when facial nerve paralysis is noticed postoperatively
Hypoglossal Facial nerve anastomosis Technique
- A parotidectomy incision is given and facial nerve is exposed.
Identify the nerve as it exits the stylomastoid foramen.
It is sharply transected here in this region. - Identify the hypoglossal nerve in the neck by following the posterior belly of the digastric muscle to the hyoid bone.
Nerve is followed distally to gain length for the anastomosis. - Transect descendants hypoglossal to gain length and mobilization for the anastomosis.
- Transect the hypoglossal nerve distally and approximate it to the facial nerve passing medial or lateral to the digastric muscle. The nerve ends are then grafted together.
Cross Face Grafting
- This procedure attmpts to connect the branches of paralyzed facial nerve to the corresponding branches on the normal side.
- It is done in cases where the proximal end of the nerve is not available for repair but the motor end plates on the
paralyzed side should be functional for the success of this procedure. - This procedure is not possible in cases in which the nerve has been paralyzed for over a year.
“Facial Asymmetry And Nerve Injury Connection“
Cross Face Grafting Technique
- Very commonly sural nerve is used to carry nerve to opposite side as it consists of adequate length to thread across from one end of the face to another.
It is indicated in cases where multiple branches are to be anastomosed.
Great auricular nerve may be used in cases when a single nerve is grafted. - Dissect affected side first and identify all the branches. If multiple branches should be grafted they are identified and exposed a litte beyond the parotid gland.
- Expose the normal facial nerve and the donors should be taken from distal border of the parotid gland.
- Now identify sural nerve and the branches should be tunneled across the face. First suture the nerve graft to the normal side and then to the chosen branch on the paralyzed side.
- For good healing meticulous hemostasis and the use of drains to prevent the formation of hematoma is essential.
- Some iatrogenic weakness is expected on the donor side after this procedure and the patient must be warned of this before going for procedure.
“Imaging Techniques For Facial Nerve Assessment”
Postoperative Care of the Patient
- As return of function takes few months with each of these procedures, attntion to patient care should be given such as eye protection.
- Various adjunctive procedures, i.e. gold weight eyelid implants or brow lift may be considered.
- Reexploration and revision should be done ifimprovement is not seen in one year following grafting.
Leave a Reply