Surgical Repair of the Traumatized Facial Nerve

Radiographic findings are extremely important in the guidance of the surgical exploration in repair of a traumatized facial nerve. Most injuries are in the vicinity of the geniculate ganglion, specifically, the proximal tympanic segment, the geniculate ganglion, or the labyrinthine segment.14 Surgical exploration of the facial nerve after temporal bone trauma is initially performed as a transmastoid approach. Canal wall-up mastoidectomy with facial recess is often adequate for surgical exploration and decompression of the facial nerve from the proximal tympanic segment through the distal vertical segment. Exploration ofthe geniculate ganglion or labyrinthine internal auditory canal segment can be performed via a middle fossa craniotomy. If the patient has suffered total sensorineural hearing loss from trauma, a translabyrinthine approach is preferable to the middle fossa approach to obtain total facial nerve exposure without temporal lobe retraction in the acute head injury scenario.

If the nerve is anatomically intact, it is widely decompressed around the fracture site, and the sheath is opened. Only spicules are removed from the facial nerve if present. A large diastasis in the course of the facial nerve usually requires facial nerve interposition graft. The greater auricular nerve is an excellent source for a grafting material. If this is unavailable, the sural nerve is another option. Interposition grafts can be placed in the trough of the fallopian canal that are held in place with absorbable hemostatic material. Sutures are required such as in the labyrinthine or proximal tympanic segments, two or three 10-0 monofilament sutures are then used. Damage in the peri-geniculate region of the nerve can require middle fossa exposure for complete visualization if hearing is intact. In cases in which hearing is not intact, the tympanic segment may be rerouted directly to the labyrinthine or internal auditory canal (IAC) portion. Suture repair or grafting of the IAC facial nerve can be technically difficult. Usually only one suture can be placed to approximate the ends of the nerves and the anastomosis is reinforced with absorbable hemostatic material.

Partial transections of the facial nerve require a difficult decision as to whether facial nerve grafting is indicated. Most surgeons would agree that if 50% or more of the facial nerve is transected, the nerve should be grafted.15 Obtaining an accurate estimation can be difficult in the face of anatomic constraints or granulation tissue. Especially in the presence of an iatrogenic injury, and because of the inability to determine the extent of injury adequately, some investigators have suggested that if the facial nerve appears to be transected greater than one-third of its diameter, it should be grafted.

If an injury to the sheath is identified with herniation of nerve fibers through the damaged sheath, a segment of the nerve on either side of the injury is decompressed, and the sheath is opened to prevent strangulation of the nerve.

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