Treatment of Small Acoustic Tumors (Vestibular Schwannomas)

Abstract

Acoustic tumors (vestibular schwannomas) are the most common tumor of the cerebellopontine angle (CPA). Microsurgical resection is the traditional method of treatment, with complete tumor removal as the goal. The translabyrinthine approach is used in patients with poor hearing or no hearing and in any tumors larger than 2.5 cm. The middle fossa approach is used for tumors up to 2 cm in size with serviceable hearing. Conservative therapy or “observation” with serial imaging is often advocated for elderly patients with smaller tumors and without significant symptoms. A more recent treatment modality is stereotactic radiotherapy, with the goal of tumor control, defined as tumor regression or stable tumor size. Different forms of radiotherapy include radiosurgery, which uses a single-fraction dose of radiation, and fractionated radiotherapy, which divides doses to minimize damage to normal tissues. Regardless of method, treatment results for small acoustic tumors are generally good, and we typically recommend early intervention. Complete tumor removal has been demonstrated in 99% of patients undergoing microsurgical resection for small tumors, with tumor recurrence rates over all tumor sizes very low (<0.3%). Most reports show good facial nerve function after treatment in >90% of patients with small tumors. Hearing preservation at serviceable levels in patients with preoperative hearing is reported at about 60% in patients with small tumors undergoing middle fossa microsurgical removal. Cranial nerve dysfunction is often delayed following radiotherapy, so tumor control rates and nerve function results with the current generation of lower dose radiotherapy procedures awaits further study.