Bacitracin--therapeutic use Cephalosporins--therapeutic use Cerebrospinal Fluid Otorrhea--prevention & control Cerebrospinal Fluid Rhinorrhea--prevention & control Humans Injections, Intravenous Intraoperative Care Meningitis--prevention & control Neuroma, Acoustic--surgery Premedication Surgical Wound Infection--prevention & control Therapeutic Irrigation Vestibular Nerve--surgery