HSC Section 8_April 2017

SRS (Fig. 1). All patients in our institution’s cohort had

proven growth of their FNS on repeat MRIs before SRS.

Only two other patients in one study (13) explicitly stated

that patients had growing FNS before SRS.

Statistical analysis was not performed because of the

small number of failures. Although the majority of patients

received gamma knife as the primary treatment modality,

all failures were also within this group. Mean marginal dose

data were available for two treatment failure patients who

received 10 Gy and 12.5 Gy, respectively. It is important to

note that one other patient received 10 Gy and had evidence

of tumor shrinkage, and seven other patients received

12.5 Gy. Of these, four (57.1%) had no tumor growth and

three (43.9%) had tumor shrinkage.

Facial Nerve Function

Thirty-nine patients in the literature had preoperative and

postoperative data with regard to FN function. The majority

(26 patients, 66.7%) showed no change in HB score. Five

patients (12.8%) developed worsened FN function, whereas

eight (20.5%) reported improved FN function. Table 1

displays FN outcomes in those patients with at least

2-year follow-up.

In looking at those whose FN function worsened, two

(40.0%) were pre-SRS HB grade I and three (60.0%)

were HB grade II. Unfortunately, data on tumor location

were only available for three patients. Notably, however,

all three had tumor medial to the geniculate ganglia (GG)

involving the IAC. With regard to treatment modality,

five (80.0%) received GK (mean margin dose, 12.8 Gy)

and one (20.0%) received LINAC (54 Gy). Again, given

the small number, it is impossible to make any statisti-

cally relevant correlations.

Interestingly, there were two patients in the literature

whose FN function improved by two HB grades (one

patient IV to II; another, VI to III). Six others improved

by one HB grade. Tumor location data were available for

seven of these patients. Of these, five (71.4%) patients

had tumor involving the GG. No patient in this group had

tumor lateral to the GG. Figure 2 displays FN outcomes

with regard to initial HB grade.

Hearing Outcomes

Twenty-six patients had available complete pre- and

post-SRS hearing data with at least 2-year follow-up. No

patient had improved hearing after SRS. Fourteen patients

had serviceable hearing (AAO

Head and Neck Surgery

[HNS] class A/B) before SRS. Of these, nine (64.3%)

showed no change in hearing class and five (36.7%) had

worsened hearing

three (21.4%) from class A to B and

FIG. 1.

In total, there were 30 patients with available and well-defined data on tumor growth with at least 2-year follow-up.

FIG. 2.

Change in FN function related to pre-SRS HB grade. Number of patients in each pre-SRS class is listed along the

axis.

SRS FOR FACIAL NERVE SCHWANNOMAS

Otology & Neurotology, Vol. 36, No. 3, 2015

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