HSC Section 8_April 2017

Stereotactic Radiosurgery for Facial Nerve

Schwannomas: Meta-analysis and Clinical Review

Theodore R. McRackan, Eric P. Wilkinson, Derald E. Brackmann,

and William H. Slattery

House Clinic, Los Angeles, California, U.S.A.

Objective:

Although several small individual series on stereo-

tactic radiosurgery (SRS) for facial nerve schwannomas (FNSs)

have been published, we aim to systematically aggregate data from

the literature as well as from our institution to better understand the

safety and efficacy of SRS for FNS.

Data Sources:

PubMed English language search for keywords

‘‘facial nerve schwannoma’’ AND ‘‘radiation therapy’’ pub-

lished from January 1995 to 2014. Data from our institution were

also included in the analysis.

Study Selection:

Minimum study inclusion criteria included

tumor treatment outcomes yielding 10 studies in the literature. In

addition, our institution’s data on six patients were included.

Data Extraction:

Data included radiation treatment type, radi-

ation dose, tumor size, tumor control, tumor control definition,

FN function, hearing outcome, and duration of follow-up.

Data Synthesis:

In total, there were 45 patients with at least 2-year

follow-up. Forty-two patients (93.3%) had tumor control. Of those

patients with described growth/shrinkage definitions, 50.0% had

no growth, 43.3% had shrinkage, and 6.7% had growth. Of those

articles that included FN functional outcomes, 26 patients (66.6%)

had stable FN function, 8 (20.5%) had improved function, and

5 (12.8%) had worsened FN function after treatment. In total,

there were 30 patients whose hearing outcomes were discussed

in the literature. Of those with serviceable hearing before SRS

(n = 14), nine (64.3%) had stable hearing and five (36.7%) had

worsened function after SRS. The mean posttreatment follow-up

period was 42.1 months.

Conclusion:

SRS seems to be effective at either stabilizing or

shrinking FNS. However, significant morbidities of FN paral-

ysis hearing loss do exist.

Key Words:

Cyberknife

Facial

nerve neuroma

Facial nerve schwannoma

Fractionated

radiation

Gamma knife

Radiation therapy

Stereotactic

radiosurgery.

Otol Neurotol

36:

393

398, 2015.

Although they represent the most common primary tumor

of the facial nerve (FN), FN schwannomas (FNSs) are rare.

Like acoustic neuromas, FNSs are benign tumors made of

Schwann cells that are slow growing and may be present

for years before symptoms arise (1). The decision of when

and how to intervene has attempted to be established (2),

but there is no clear consensus.

FNSs pose a significant dilemma to the treating physician.

First, they can arise anywhere along the FN (3,4) and may

be mistaken for acoustic neuromas when isolated to the

cerebellopontine angle (CPA) and internal auditory canal

(IAC) (4,5). Second, given that FN fascicles have been shown

to run through the schwannoma (6), operative intervention is

limited to FN decompression or debulking versus resecting

the involved FN segment with direct anastomosis or graft

when necessary. Third, data on stereotactic radiosurgery

(SRS) are limited to small single-institution case series that

often provide inconsistent information with regard to FN

and hearing outcomes.

If SRSs were able to stop or reverse the growth of FNS,

it may be a reasonable initial treatment option if FN

function and hearing did not appreciably suffer. Simi-

larly, SRS may also be used as adjuvant therapy in pa-

tients whose FNSs continue to grow after undergoing FN

decompression. Unfortunately, SRS data on FNS have

yet to clarify these questions. Our study attempts to

systematically pool the literature on this topic in the hope

of better understanding the control rates and side effect

profile of SRS for FNS.

METHODS

Data Sources/Study Selection

PubMed English language search was conducted for articles

on radiation treatment of FNS published from January 1995 to

August 2014. This time frame was used because SRS practices

during this period reflect modern dosing strategies. Key word

Address correspondence and reprint requests to William H.

Slattery, M.D., 2100 West 3rd Street, Los Angeles, CA, U.S.A.;

E-mail:

wslattery@houseclinic.com

The authors disclose no conflicts of interest.

This article will be presented at the 2015 American Neurotology

Society meeting in Boston, MA, U.S.A.

Otology & Neurotology

36:

393

398 2015, Otology & Neurotology, Inc.

Reprinted by permission of Otol Neurotol. 2015; 36(3):393-398.

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