Objective: In vestibular schwannoma surgery four different intraoperative BAEP pattern – stable BAEP, abrupt loss, irreversible progressive loss, reversible loss -can be identified and correlated with postoperative hearing outcome. Patients with reversible loss significantly benefit from postoperative vasoactive treatment consisting of hydroxyethyl starch and nimodipine. The present study investigates the treatment effect in the remaining three BAEP pattern.
Methods: A retrospective analysis was performed in 92 patients operated upon for vestibular schwannoma between 1997 and 2005. Between 1997 and 2001, only patients with reversible loss of BAEP received vasoactive medication. Subsequently, all patients operated upon between 2001 and 2005 received a 10-day-course of therapy, regardless of BAEP pattern. Serial audiological examinations before, after surgery, and after one year were performed in all patients.
Results: All 30 patients with reversible loss of BAEP received medication, postoperative hearing preservation was documented in 21 patients. All 13 patients with stable waves showed hearing preservation, regardless of treatment. In all 24 patients with abrupt loss and in all 25 patients with irreversible progressive loss postoperative anacusis was documented, regardless of treatment.
Conclusion: In patients with reversible loss of BAEP a disturbed microcirculation of the cochlear nerve seems to be the underlying pathophysiological factor. In patients with abrupt or irreversible progressive loss, additional mechanical injury of nerve fibres determinates hearing outcome. The study gives evidence, that for the purpose of hearing preservation only patients with reversible loss of BAEP benefit from vasoactive treatment.
- hearing preservation
- hydroxyethyl starch
- intraoperative BAEP pattern
- vestibular schwannoma surgery