The Prognostic Value of the Glycerol Test: A Review of 60 Ears with Unidirectional Inner Ear Valve Implants

Abstract

The following are our conclusions in regard to glycerol test interpretation based on 60 valve implants: Negative Tests 1. A negative glycerol test result and no audiometric evidence of significant hearing fluctuations indicate that a patient is unlikely to have postoperative hearing that is better than his best preoperative hearing. 2. The patient with a negative test can still have an excellent chance (greater than 80 per cent) to be relieved of vertigo. 3. A negative test and no audiometric evidence of significant hearing fluctuations in a patient with cochlear Meniere's disease would contraindicate valve surgery. Positive Tests 1. A positive glycerol test, done under appropriate conditions with adequate audiometric controls, clinically confirms the histopathologic diagnosis of endolymphatic hydrops. 2. The patient will have a 30 to 40 per cent chance of having better postoperative hearing than his best preoperative hearing. 3. The patient will have an 80 to 90 per cent chance to be free of vertigo. 3. The patient will have an 80 to 90 per cent chance to be free of vertigo. 4. A positive glycerol test would be a contraindication for labyrinthectomy, since the patient has the potential for some hearing improvement as well as absence of vertigo.