New-onset facial spasm is associated with treatment failure after radiosurgery in vestibular schwannoma.

BACKGROUND

New-onset facial spasm (NOFS) has been reported to be a post-therapeutic side effect, when treating vestibular schwannoma (VS) with radiosurgery (SRS) and has been linked to post-treatment pseudoprogression. The aim of this study was to identify risk factors for developing NOFS after SRS treatment and to investigate NOFS as a clinical parameter for radiographic tumor response in VS.

METHODS

This study included all consecutive patients of = 1,998 between 2004 and 2020, which were treated with SRS identified by a prospective registry. Patient and tumor characteristics (ie, sex, age, tumor extension and size, and intracanalicular extension) were analyzed retrospectively. Statistical testing was performed with R Studio.

RESULTS

The incidence of NOFS was 5% overall. In total, 62% were permanent NOFS, whereas 39% recovered spontaneously between 4 and 34 months, postinterventionally. The incidence of NOFS was unrelated to tumor volume-however, previous SRS increased the incidence of NOFS to 20%. In primary SRS therapy, facial spasm was associated with a higher recurrence rate compared to non-NOFS patients in the Kaplan-Meier analysis ( < 0.001). Tumor control decreased with increasing tumor size. The rate of pseudoprogression was higher in the group of transient NOFS at 39% compared to permanent NOFS at 18% ( = 0.032).

CONCLUSIONS

The risk of NOFS was significantly higher in recurrent compared to primary treatment (20% vs 5%) and the majority of NOFS was permanent. The incidence of permanent NOFS was significantly associated with treatment failure. Temporary NOFS was associated with pseudoprogression. Future analysis comparing the risk profile of either treatment option should include facial spasm as a significant VS-related postinterventional symptom. Patients with postinterventional NOFS should be followed-up long-term for higher risk of treatment failure.