Caloric Function After Endolymphatic Sac Surgery

Objective: To evaluate the effect of endolymphatic sac surgery on vestibular functions using caloric testing on electronystagmography (ENG). Study Design: Retrospective chart review. Methods: The medical records of 21 adult patients with unilateral Meniere's disease who underwent endolymphatic sac surgery between 1998 and 2004 were reviewed. With use of ENG, the absolute value of the caloric response of the operated ear (i.e., the cool + warm irrigation response) and the degree of reduced vestibular response (RVR) rates as indicators of caloric functions were compared before and after surgery. Average follow-up was 17 (6-52) months. Results: The mean change in RVR after surgery was found to be 2.9%. In total there were six (28.5%) patients who had an RVR increase more than 10%. Of those, there were three (14.2%) patients who demonstrated an RVR increase more than 20%. Only one (4.8%) patient had an RVR increase more than 30%. Total loss of vestibular function was not observed in any of the patients. There were three (14.2%) patients who exhibited a decrease of more than 10% in their RVR. In two (9%) patients, the contralateral ear was shown to have less vestibular function than the operated side on ENG postoperatively (in one case, the absolute caloric nystagmus response remained the same in the operated ear, and in the other case, the response increased on the surgical side). When we evaluated the absolute caloric responses of the operated ear only, we found no statistical difference between the pre- and postoperative values (P = .219). Early results of vertigo control and hearing outcomes were comparable with those in the literature. Conclusion: Endolymphatic sac surgery does not appear to be a vestibular destructive procedure, and it is a therapeutic alternative for patients with Meniere's disease who have failed medical treatment. This is important given the possibility of bilateral disease in some patients.