Intratemporal Tumors of the Facial Nerve Treatment & Management

In patients without facial dysfunction, a conservative strategy consisting of clinical and radiological observation should be considered as a treatment option. When facial nerve paralysis has developed to a House-Brackmann grade of more than III, an immediate operation is recommended to obtain a good postoperative facial functional recovery. On the other side of this debate, some experts report early schwannoma resection with facial nerve preservation. Little data have been published on the use of radiotherapy to treat facial nerve tumors.

Surgical resection of facial nerve neuromas is also indicated when a large cerebellopontine angle tumor compresses the brainstem or results in hydrocephalus. Note that brainstem compression and hydrocephalus are far more common among cases of vestibular schwannoma rather than facial nerve tumors. Other operative indications include tumor invading the inner ear or suspicion of malignancy or neurofibromatosis 1.^[3]

Surgery is the preferred therapeutic modality for advanced schwannomas and hemangiomas of the facial nerve. The surgical approach depends on the anatomic location of the tumor, the extent of the tumor, and the hearing status in both ears. Timing of surgical intervention presents a thornier dilemma.^[4]

Hemangiomas, with their proclivity to arise from the geniculate ganglion, are often confined to the middle cranial fossa and can therefore be removed via a subtemporal craniotomy. If the tumor extends laterally down the labyrinthine segment or along the tympanic segment of the facial nerve, a combined approach that incorporates a postauricular mastoidectomy may be necessary. A transmastoid approach is usually preferred. Since hemangiomas are extraneural, they can, if small, be removed while sparing the facial nerve.

Surgical removal of facial nerve schwannomas is approached similarly. These tumors are more likely to extend into the cerebellopontine angle and therefore may also reach a larger size before they become symptomatic. However, often the diagnosis of facial nerve schwannoma can only be made intraoperatively during removal of what had been regarded as a vestibular schwannoma.

In patients with residual or recurrent intracanalicular neuromas, the translabyrinthine approach is the preferred surgical route, allowing complete tumor removal; it may also be used for exposure of the intratemporal portion of the facial nerve for a hemihypoglossal-facial nerve anastomosis when a postoperative facial palsy exists. The facial nerve is exposed in its mastoid and tympanic parts, mobilized, and transected. Then, the long nerve stump is transposed into the neck and used for an end-to-side anastomosis with the hypoglossal nerve, although end-to-end anastomosis of distal facial nerve to its proximal counterpart is preferred with the removal of an intracanalicular residual schwannoma. Neurotization of the facial muscles through a nerve graft may be used when no distal trunk of the facial nerve is available for the anastomosis.

The translabyrinthine or transpetrosal route is useful for patients without useful hearing and a facial nerve neuroma in the internal auditory canal. In patients with useful hearing, a hearing-sparing approach (eg, middle fossa approach) is used. However, the middle fossa approach involves retraction of the temporal lobe.

Clinicians should beware that, although radiation doses delivered to middle and external ear structures are unlikely to contribute to post–gamma knife surgery complications, unexpectedly high doses may be delivered to sensitive areas of the intratemporal facial nerve. Rare cases of intratemporal facial nerve tumors are reported in the stereotactic radiosurgery literature. Therefore, data available are insufficient to determine whether this treatment modality is safe.

Follow-up and appropriate timing of intervention are the key issues in managing patients with intratemporal facial nerve tumors. If a 3-mm hemangioma is discovered at the geniculate ganglion, it may be amenable to being stripped off of the nerve such that the nerve is left intact, but often, the tumors are larger. Hemangiomas insinuate between the nerve fibers, making nerve-sparing dissection difficult. Schwannomas often are tightly integrated into the nerve such that no safe surgical plane is identifiable. Thus, removal of these tumors endangers nerve integrity and function.

Because of the high likelihood that the facial nerve will be resected along with the tumor, a primary anastomosis (for smaller tumors) or a cable graft (using great auricular nerve, sural nerve, most commonly) may be required. Because the best expected functional result with these nerve repair techniques rarely exceeds a House-Brackmann grade III paresis, intervention is timed such that facial nerve function has degenerated to worse than House-Brackmann IV or so. However, intervention should not be delayed past the point where motor endplates have atrophied.

Obviously, patients need close follow-up on an outpatient basis in the surgeon's clinical practice. Patients should understand the nature of their disease and the rationale behind the timing of intervention to be better able to incorporate those considerations into the decision-making process.

Finally, the decision on how to treat these patients should be individualized and based on initial facial function, growth rate, surgical experience, and informed patient consent.

Complications of surgery for facial nerve tumors are related to the surgical approach. For craniotomies, these complications include but are not limited to cerebrospinal fistula, seizures, hydrocephalus, meningitis, and possible loss of any and all neurologic functions. Complications of mastoid or translabyrinthine approaches include hearing loss, tinnitus, vertigo, infection, and hematoma. Discuss facial paralysis with the patient, so that expectations for functional recovery are realistic. Most patients who had worse than moderate facial palsy can expect no better.