Predictive factors of facial nerve function after medium/large vestibular schwannoma surgery: relationships between time of surgery, dimensions and size of resection

Background Vestibular schwannomas (VS) are slowly growing tumor, deriving from the vestibular component of cranial nerve VIII. Primary treatment modalities include microsurgery, radiosurgery, a combination of microsur- gery and radiosurgery, and conservative treatment. The management of VS is a matter of debate, particularly in case of small tumors (less than 2 cm in diameter size). Methods We performed an institutional retrospective review of a consecutive series of 28 surgically treated patients suffering from VS, operated in our institution. Patients were assigned on the ground of the preoperative imag- ing in two groups: tumors with major diameter of extra-meatal portion measuring ≥ 3 cm (Group I, 16 patients) and tumors with major diameter < to 3 cm (Group II, 12 patients). Results The total amount of 18/28 patients were females; the average age was 60.1 years. The average duration of the preoperative symptoms was 25.2 months, while the average interval between the diagnosis and surgical treat- ment was 8.68 months. The average preoperative volume was, respectively, for Group I and II tumors of 14.35 cm3 and 3.73 cm3. Age was associated to the duration of the preoperative symptoms (r = − 364; p = 0.044), with the prob- ability to develop a complication (p = 0.031) and preoperative low HB score (r = − 324; p = 0.040). The presence of hypoacusis as preoperative symptom was strongly associated to a lesser postoperative maximum diameter and smaller residual disease (p = 0.014). Group I had a significantly longer hospitalization period in respect to Group II (p = 0.001) that impacted negatively to postoperative performance status (r = 0.368, p = 0.042). Conclusions We confirmed the strong association between age and size of the lesion and the clinical results, where larger lesions in older patients are more prone to complications than smaller in young patients. We found that the patients presenting hypoacusis at onset were associate to lesser preoperative FN impairment outlining a possible differential involvement of the CN related to the internal meatus. We also introduce the strong association of Koos grade with postoperative performance status, hospitalization and facial nerve functionality.