A Preliminary Report on the Correlation of Vestibular Meniere's Disease with Electrocochleography and Glycerol Test

Abstract

Objective evaluation of vestibular Meniere's disease has been difficult due to the lack of audiometric findings. Thus inevitably, the existence of vestibular Meniere's disease is constantly being challenged. In recent years, electrocochleography (ECochG) has proved to be a useful tool to verify the presence of endolymphatic hydrops electrophysiologically. To further clarify the nature of this disease, we collected 40 patients prospectively who met the following conditions as diagnostic criteria for clinical vestibular Meniere's disease: i) episodic vertigo, ii) aural fullness, and iii) normal hearing. We implemented the glycerol test and extratympanic ECochG in addition to routine survey in these cases. The diagnosis was confirmed if either test result was positive. A retrospective collection of 24 cases who underwent endolymphatic sac surgery was made to evaluate in retrospect the existence of endolymphatic hydrops indirectly proved by successful surgery. Results showed a positive SP/AP ratio in 25 cases (62.5%) of which 7 had bilateral positive responses. The glycerol test was positive in 5 cases including 3 who also had positive ECochG responses. In the retrospective group, 4 cases exhibited an abnormally large SP/AP amplitude ratio at preoperative baseline conditions after general anesthesia. Twenty cases showed an SP/AP ratio within normal limits. Only 7 cases (29%) showed a decrease in the SP/AP ratio at different surgical steps. Short-term surgical results showed a 96% success rate of relief of vertiginous symptoms. Symptoms of fullness were completely controlled in 22 patients (92%). Hearing was preserved in 18 patients (75%). We conclude that i) the above-listed clinical criteria combined with these objective tests may prove to be very useful in the diagnosis of vestibular Meniere's disease, and ii) a successful control of vertigo and aural fullness after endolymphatic sac surgery indirectly indicates that endolymphatic hydrops is involved in vestibular Meniere's disease, sharing as it does, a pathophysiology that is similar to that of classic Meniere's disease.

Key Words:

• summating potential
• SP/AP ratio
• endolymphatic hydrops