Position and Course of Facial Nerve and Postoperative Facial Nerve Results in Vestibular Schwannoma Microsurgery

To investigate the variation in the position and course of facial nerve (FN) in patients undergoing vestibular schwannoma (VS) microsurgery by key-hole retrosigmoid approach and the relationship between its position and postoperative facial results.
The series consists of 100 patients who underwent VS microsurgery during a 5-year period, in whom the position and course of the FN could be confirmed by direct stimulation. In relation to the position of FN, patients were classified into four groups: anterior (ventral) surface of the tumor (A), anterior-superior (AS), anterior-inferior (AI), and dorsal (D).
The FN position and course was AS in 48 cases, A in 31, AI in 21 and D in zero. For tumors <1.5 cm, AS position was most common (68,4%). For tumors ≥1.5 cm, the proportion of A and AI increased (31,4% and 25,5%) respectively). Significant differences were observed between position and course patterns of the FN and postoperative nerve results: AS and AI had better House-Brackmann (HB) FN function in comparison to A group (p<0.05). Moreover, in tumors >3.0 cm, the FN had the tendency to adhere strongly to the tumor capsule, and postoperative facial deficit were more frequent (p<0.05).
The AS pattern was most common for smaller VS. The A position and course and adhesion of the nerve to the tumor capsule were the two factors most strongly associated with worst postoperative FN result.