Surgery a Viable Option for Treatment for Rare Facial Nerve Tumors

A diagnosis of intratemporal facial nerve schwannomas or nerve tumors is uncommon with less than 600 reported in medical literature. These benign, encapsulated neoplasms can occur in any segment of the facial nerve and will often involve a number of segments. Clinical presentation varies widely and ranges from asymptomatic (incidental finding) to total facial nerve paralysis and/or deafness. The definitive treatment for this entity is complete surgical excision. Because the tumor is extremely slow growing, frequently diagnosed in individuals with normal facial function and the results of excision highly variable, some authors recommend ongoing observation combined with serial radiological examination or partial removal (decompression).

Surgical treatment classically consists of excision of the lesion with the involved segment of the nerve followed placing a graft to rejoin the affected nerve. However, there have been only a small number of reports of tumor excision that leave the nerve intact and functioning. The present study highlights a relatively large series of patients with facial schwannoma who were managed surgically and expectantly. In the surgically managed group of individuals the decision to proceed with tumor removal was made at/near the time of diagnosis. The objectives are to report the long-term results in both groups as it relates to facial nerve function and hearing. The surgical approach and the strategy employed attempting to preserve facial nerve integrity are highlighted in the surgical group and the growth rate assessed by magnetic resonance imaging (MRI) in those individuals followed expectantly.

The authors of "Intratemporal Facial Nerve Schwannoma: A Management Dilemma" are Ronen Perez MD, Joseph M Chen MD, Julian M Nedzelski MD Department of Otolaryngology, Sunnybrook and Women's College Health Science Centre and the University of Toronto, Toronto, Ontario, Canada. Their findings are being presented at the annual meeting of the American Neurotology Society http://www.otology-neurotology.org/ANS/ans-mai being held April 30-May 3, 2004, at the JW Marriott Desert Ridge Resort & Spa, Phoenix, AZ.

Methodology: Twenty-six patients with facial nerve schwannomas were treated in an otolaryngology department between 1979-2004. With exclusions, the study group consisted of 24 patients with a mean age of 44 ± 14 years ranging from 18 to 65 years. There were 13 males and 11 females.

Thirteen patients were managed expectantly (or watchful waiting) and 11 patients treated surgically. The 13 patients treated expectantly were followed up using a combination of clinical examination and imaging. Tumor size was measured using MRI scans; the mean follow up interval between initial diagnosis and last imaging scan and examination performed was 5 years ranging from 1 to 8 years. Seven of 11 patients of the surgical group had their tumor removed leaving the nerve intact; three underwent sural nerve grafting and one, primary anastomosis or joining together of the nerve. The mean follow up between surgery and the last clinical examination was 8 years ranging from four to 19 years.

Facial nerve function and hearing outcome were determined at the time of the last visit and compared to function at initial presentation.

Results: Twenty-three out of the 24 tumors involved more than one segment of the facial nerve. The most frequently involved were the geniculate ganglion (16 patients); tympanic segment of the nerve (14 patients), and the least frequent area involved was the internal auditory canal and cerebellopontine angle (CPA)(four patients).

The most frequent clinical signs on presentation were facial weakness (12 patients) and hearing loss (12 patients) Three patients had previous ipsilateral sudden onset facial paralysis with varying degrees of recovery, five had aural fullness, three tinnitus and three vertigo or imbalance. Half the patients had normal facial function at presentation. The findings of the research revealed:

The facial nerve was spared in seven of the 11 patients who underwent tumor removal. Eight had varying degrees of facial nerve dysfunction initially. In this group, (mean follow-up eight years) six patients had unchanged nerve function, four improved and one worsened. No recurrence was noted. Of the 13 patients followed expectantly or with watchful waiting, three had facial weakness initially. During the follow-up interval (mean five years) facial function remained unchanged for eight and worsened in five. During this interval five patients demonstrated tumor growth. Two patients have recently undergone tumor removal and a third is awaiting surgery.

Conclusions: The authors suggest that based on their findings, tumor should be removed with careful intracapsular piecemeal bulk reduction similar to the strategy employed in acoustic neuroma removal. Facial nerve monitoring and intraoperative stimulation are critical. Clearly, the results of the study suggest that final facial nerve function in some cases where this has been successful is superior to those optimally expected where an interposition graft has been used. This study asserts that an individual diagnosed with an intratemporal facial schwannoma in whom facial function is normal, likely has the best opportunity at a better outcome should he/she decide to undergo removal in the hope that facial nerve preservation is possible. The caveat that bedevils all clinicians is the inability to predict outcome and the realization that facial nerve function can remain normal or nearly so for many years prior to surgical treatment being required.

The advocates of watchful waiting may point to the fact that these tumors are extremely slow growing and frequently present without facial dysfunction. These findings prove it is possible to surgically remove the tumor while sparing the nerve resulting in better postoperative facial function. Surgery is the definitive treatment. The decision to operate or to observe should be individualized and based on initial facial function, rate of tumor growth, and the experience of the surgeon and patient informed consent. When proceeding with surgery an attempt should always be made to spare the nerve given the possibility of a superior outcome.