SUMMATING POTENTIALS IN MENIERES-DISEASE

The summating potentials in response to tonebursts of 2, 4 and 8 kHz were studied in a group of 112 patients diagnosed as having Meniere''s disease, and the results were compared with recordings from 27 normal human ears. Subdivision of the Meniere ears into a low-threshold (threshold < 50 dB HL [intensity value]) and a high-threshold group (> 50 dB HL) proved to be functional in relation to the behavior of the SP [summating potential, a wave form]. The data of the low-threshold Meniere group did not differ significantly from the normal data, whereas the high-threshold Meniere group showed significantly smaller summating potentials. Up to hearing thresholds of 50 dB, the detection threshold for the SP was independent of the hearing threshold; at higher hearing losses, the increase in SP threshold equaled the increase in hearing loss. Analysis showed that the correlation between the changes in SP and hearing threshold in individual patients did not differ significantly from zero for threshold values below 50 dB. In Meniere ears hearing losses up to about 50 dB are not related to changes in the hair cells, since the SP does not change, whereas the increase in the amount of hearing loss above 50 dB HL is paralleled by a loss in sensitivity of the summating potential and is therefore related to a functional loss of hair cells.