Vestibular evoked myogenic and periocular potentials after vestibular schwannoma surgery

Objectives: We analyzed the behavior of preoperative and postoperative vestibular evoked myogenic potentials (VEMPs) and vestibular evoked periocular potentials (VEPPs) in 3 patients who had vestibular schwannoma and underwent modified translabyrinthine surgery. Methods: We compared VEMPs and VEPPs, measured with both air-conducted (AC) and bone-conducted (BC) stimulations. Vestibular evoked potentials were measured both in the immediate postoperative period and some months later. Results: At the immediate postoperative examination, VEPPs were preserved in all 3 patients with both AC and BC stimulations. The VEMPs showed stable or improved parameters in 2 of our patients and were absent in the third patient. At the follow-up examination, VEMPs did not show any significant change with respect to the previous evaluation: In contrast, VEPPs were absent in 2 of our patients with AC stimulation and in I patient with BC stimulation. Conclusions: Our results seem to indicate a greater stability and reproducibility of VEMPs compared with VEPPs. In 1 patient, who had a schwannoma of the inferior vestibular nerve, the preservation of VEPPs and the absence of VEMPs in the immediate postoperative period confirm that the saccule represents the origin of VEMPs. Furthermore, these results suggest that not only the saccule, but also the utriculus, could be implicated in the origin of VEPPs.