HSC Section 8_April 2017

SRS FOR FACIAL NERVE SCHWANNOMAS

FIG. 1. In total, there were 30 patients with available and well-defined data on tumor growth with at least 2-year follow-up.

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 Y 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 V three (21.4%) from class A to B and

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%)

FIG. 2. Change in FN function related to pre-SRS HB grade. Number of patients in each pre-SRS class is listed along the x axis.

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