Analytic view to concordance between electrocochleography and caloric test in Meniere's disease

We aimed to investigate if there is a concordance between summation potential (SP)/action potential (AP) ratio and unilateral weakness in patients with definite-Meniere's disease. There were two groups, a group of unilateral definite-Meniere patients who received no treatment and another group of control subjects. Twenty-six patients were identified as complying with the defined criteria. Fifteen healthy subjects with no hearing and balance disorders were assigned to the control group. Arithmetic mean of the four-tone average of thresholds at 0.5, 1, 2, and 3 or 4 kHz, SP/AP ratio and degree of unilateral weakness were calculated. The number of patients was tabulated based on the presence of abnormal SP/AP ratio and unilateral weakness. Co-occurrence of unilateral weakness and elevated-SP/AP ratio was investigated with reference to the stage of the disease. A correlation was sought among pure-tone average, SP/AP ratio and degree of unilateral weakness in a pair-wise manner. Unilateral weakness and abnormal SP/AP ratio were identified in 53.8% and 38.4% of the patients, respectively. Co-occurrence of unilateral weakness and abnormal SP/AP ratio was observed in 34.6% of the patients. However, it was noticed that this co-occurrence gradually increased when the disease progressed. Mean SP/AP ratio also gradually increased as the stage progressed. Of pair-wise correlations among pure-tone average, SP/AP ratio and degree of unilateral weakness, a weak correlation (r = 0.383) was found only between SP/AP ratio and degree of unilateral weakness with marginal significance (P = 0.053). We concluded that co-occurrence of unilateral weakness and elevated SP/AP ratio increases when the disease progresses. This co-occurrence is less encountered in earlier stages. This difference might be resulted from a difference in distension capability of the endolymphatic space of the cochlea and the vestibule. Albeit weak, there was a correlation between mean SP/AP ratio and degree of unilateral weakness, which suggests that the disease parallelly disturbs the lateral semicircular or cochlear functions especially in advanced stages.