Auditory evoked potentials--the cochlear summating potential in detection of endolymphatic hydrops.

With an expanded clinical and normative SP amplitude series, we have re-examined the incidence of SP enlargement in clinically defined Meniere and cochlear ears. The overall incidence of SP enlargement in the expanded series is somewhat less than that found in our previous study (56% versus 68%). This difference may be due to considerable preselection of patients included in the previous smaller clinical population, since many of these patients were recruited for the study because of diagnosed Meniere's disease. In contrast, the present, larger clinical population was selected from our normal service referral base, and thus contains a much higher percentage of diagnostic problems. The comparison between SP enlargement and hearing levels demonstrates that the SP test for Meniere's disease must be interpreted in the light of high-frequency hearing levels. If the patient has normal or near-normal hearing (4- to 8-kHz hearing levels 25 dB or less), SP enlargement will not be a good criterion for detecting the presence of Meniere's disease. Gibson and colleagues and Kumagami and associates have reported similar observations. Also, in the presence of severe high-frequency hearing loss (above about 70 dB), SP enlargement occurs relatively infrequently among ears with clinical diagnoses of Meniere's disease. However, in the mid-range (25 to 70 dB) of high-frequency loss, SP enlargement appears to provide a reasonably accurate test for Meniere's disease (with a "hit rate" among clinically defined Meniere ears of about 71%).(ABSTRACT TRUNCATED AT 250 WORDS)