Autogenous sensory nerve grafts should be used if you find a gap in the facial nerve that cannot be primarily repaired. The length of the graft should be about 20% longer compared to gap. The graft should also be placed in a tissue bed that is free of charge of scar. Ipsilateral cervical plexus nerves would be the first choice, then the contralateral cervical plexus.
These usually can provide adequate length (about 10 cm) when several nerves are sewn together. If greater length is needed, the sural nerve can offer as much as 40 cm of length. A number of "sleeves" have been designed to cover the suture lines. These range from simple silastic tubes to collagen tubes lined by Schwann cells. Most of these haven't demonstrated any significant benefit.
The classic teaching is that peripheral nerve axons regrow at a rate of about 1 mm daily. However, this does not look at the time required for the reinnervated muscle to regain tone and function. For most patients, return of facial movement takes 1-2 years depending on the entire graft. Movement usually begins in the oral commissure then motion around the eyes and the cheek. The muscles from the forehead and lower lip, however, usually do not regain much movement.
This technique is utilized when direct repair or grafting isn't feasible. This can be because of the lack of the main trunk of the facial nerve or in cases of intracranial nerve damage. It takes adequate mimetic muscle function and an intact peripheral nerve stump.
It involves transferring one from the other cranial motor nerves, most commonly the hypoglossal nerve. Other nerves that happen to be used include the phrenic, accessory or glossopharyngeal nerve. Nerve transfer is going to be successful in most patients, even though it often results in mass movement.
Following a cross-over procedure, the donor nerve target muscle loses some of its bulk and function. Normally , this is not really a major issue since the tongue receives innervation from several nerves. One drawback to this method is that eating and speaking can produce involuntary motion in the face.
This method employs a nerve graft (often the sural nerve) that provides a conduit for motor axons from the normal, contralateral facial nerve. Usually a single graft is used; although some people might surgeons will use multiple grafts from the intact contralateral divisions towards the corresponding paralyzed ones. Cross-face grafting can be carried out in just one stage or as a two-stage procedure.
The advantage of the two-stage procedure is that it allows the surgeon to ensure that the axons have successfully grown towards the opposite side before connecting the nerve to the injured side. In the initial procedure, the desired branch is identified on the normal side and confirmed with a nerve stimulator. The sural nerve graft is sewn into it and then tunneled subcutaneously either above the upper lip or below the lower lip. A clip is connected to the end from the nerve graft.
The second procedure is conducted about 12 months later, following a Tinel's sign is present at the distal end of the nerve graft. Any neuroma evident should be resected just before sewing the nerve graft to the injured nerve stump. The disadvantages of the cross-face graft include an additional donor site in the leg, violating the normal side of the face, two or more suture lines for that axons to cross, an extended interval until return of function and reduced motor output in the donor side.
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