Background: In patients undergoing microsurgical resection of a vestibular schwannoma, the facial and vestibulocochlear nerves are at risk. Prior studies suggested positive effects of nimodipine for preservation of the nerve function in these patients. A prospective, randomized, placebo controlled double-blinded study will be conducted to evaluate the neuro-protective effect of locally administered nimodipine during resection of vestibular schwannomas. Investigational drug: active group: Nimotop® 10mg - Infusionsflasche placebo: Natrium chloratum physiologicum 0,9% - Medica Infusionslösung Rationale for the study: Nimodipine is supposed to counteract the vasoconstriction of cerebral arteries caused by microsurgical manipulation and might thereby preserve facial and cochlear nerve function Aims of the study: Evaluation of the effect of intraoperative local administration of nimodipine on the postoperative function of the facial and vestibulocochlear nerves after microsurgical resection of vestibular schwannomas Study design: prospective, double-blinded, single-center, randomized phase III trial Study population: Patients undergoing microsurgical resection of a vestibularis schwannoma with a maximum diameter of 10-25mm on MRI at the Department of Neurosurgery, Medical university of Vienna. Number of Patients: 30

Methods: In 15 patients, nimodipine will be administered locally to the facial and vestibulocochlear nerves during resection of a vestibular schwannoma (= treatment group). In another 15 patients, a placebo (sodium chloride solution) will be administered. In both cases, a soaked gel foam pad will be used. The operating team and the patient will both be blinded during the procedure. Facial nerve function and hearing will be assessed prior and three months after surgery. Outcome variables: Serviceable or non-serviceable hearing according to Gardner-Robertson hearing scale and House-Brackmann score for the assessment of facial nerve function Statistical analysis: For the evaluation of the postoperative function of the vestibulocochlear nerve, the number of patients with postoperative serviceable hearing (Gardner-Robertson I-II) and postoperative non-serviceable hearing (Gardner-Robertson III-V) will be compared between both groups. For the evaluation of the facial nerve function, the number of patients with favorable postoperative outcome (House-Brackmann I-III) and non-favorable postoperative outcome (House-Brackmann IV-VI) will be compared. In both cases, fisher's exact test will be used. Expected risks/inconveniences: Administration of nimodipine is associated with the following adverse effects: thrombocytopenia, allergic reactions, headache, tachycardia, hypotension, nausea (occasionally) and bradycardia, ileus, reversibly elevated liver enzymes (seldom) Risk/benefit assessment: Expected adverse effects of local nimodipine administration are manageable and patients may profit from the use of nimodipine. No severe adverse events are expected.