Characteristics of 629 vestibular schwannomas according to preoperative caloric responses.

OBJECTIVES

To assess the contribution of preoperative caloric responses in patients with vestibular schwannoma on the following: preoperative parameters and postoperative results (facial function and hearing preservation).

STUDY

DESIGN

Retrospective review of prospectively collected data.

SETTING

Tertiary referral center.

PATIENTS: A group of 629 patients who underwent vestibular schwannoma surgery.

MAIN OUTCOME MEASURES: Caloric responses are quantified in terms of slow-phase nystagmus velocities generated during warm and cool irrigations of each ear, with asymmetry between the two horizontal semicircular canals was quantified by the Jongkees formula. When unilateral weakness (UW) was less than 20%, caloric response was regarded as normal (group N). When UW was greater than 70%, caloric response was classified as severe caloric weakness (group S), and when the UW was comprised between 70 and 20%, caloric response was classified as moderate (group M) caloric weakness (CW).

RESULTS

47.8% of the studied patients were included in group S, 38.2% in group M, and 14% in group N. Preoperative mean hearing loss was higher in group S compared with that in groups M and N. The auditory brainstem response threshold was higher in group S compared with that in group N and also higher in group M compared with that in group N. A good correlation was observed between CW and tumor size. Postoperative facial palsy was more frequent in group S compared with groups N and M. Postoperative hearing preservation was more frequently observed in group N compared with groups S and M.

CONCLUSION

Our results suggest that caloric responses are well correlated with the studied preoperative and intraoperative factors and provide predictive factors with regard to postoperative facial palsy and hearing outcome.