Outcomes of early microsurgical treatment via the middle cranial fossa approach in newly diagnosed patients with intracanalicular vestibular schwannoma

This study aims to evaluate postoperative nerve function and clinical outcomes in patients with newly diagnosed intracanalicular vestibular schwannoma (ICVS) following surgical resection via the middle cranial fossa (MCF) approach. A secondary objective was to explore the predictive value of preoperative assessments for determining the nerve of tumor origin, with the goal of optimizing patient selection and functional preservation. A retrospective analysis was conducted on 44 patients diagnosed with ICVS from January 2018 to January 2023. All patients either received their initial diagnosis at our department or were diagnosed at other hospitals and subsequently referred to our department for further treatment without prior intervention. Perioperative data were collected to evaluate the immediate postoperative and long-term facial and auditory nerve function of these newly diagnosed patients. Gross total resection was achieved in 97.7% (43/44) of patients. Hearing preservation (HP) was achieved in 65.9% (27/41) of patients immediately postoperatively, declining to 61.0% (25/41) at one-year follow-up. Preoperative hearing levels and the nerve of tumor origin were associated with postoperative HP. Immediate postoperative facial nerve function was significantly poorer in the T1C type compared to the T1A and T1B types (p = 0.023 and p = 0.013, respectively), with no significant difference between T1A and T1B (p > 0.05). At six-month follow-up, no significant differences in facial nerve recovery were observed among the three types (p > 0.999, p = 0.172, and p = 0.466, respectively). The accuracy of vestibular evoked myogenic potential (VEMP) testing in predicting tumor origin was 56.4% (22/39), while magnetic resonance imaging (MRI) achieved a predictive accuracy of 59.0% (23/39). The combination of VEMP and MRI improved the predictive accuracy to 71.8% (28/39) for determining the nerve of origin in patients with ICVS. Early microsurgical intervention via the MCF approach represents a feasible strategy for functional preservation in patients with newly diagnosed ICVS. However, the absence of a concurrent control group limits the ability to draw definitive conclusions regarding its superiority over observation or radiosurgery, particularly in patients with good preoperative hearing. Furthermore, the combined use of VEMP and MRI shows promise in predicting the nerve of tumor origin in most cases, though further refinement is needed to enhance accuracy.