Clinical significance of the summating potential-action potential ratio and the action potential latency difference for condensation and rarefaction clicks in Meniere's disease.
OBJECTIVE
This study was aimed to elucidate the diagnostic significance of the summating potential (SP)-action potential (AP) ratio and the AP latency difference between condensation and rarefaction clicks (AP con-rar difference) in Meniere's disease.


METHODS
The AP and SP were recorded transtympanically in 67 patients with definite Meniere's disease. The SP/AP ratio and the AP con-rar difference were assessed in terms of 1) their interrelationship, 2) their relationship to hearing level, and 3) the rate of occurrence of abnormal values according to the stages of Meniere's disease.


RESULTS
No correlation was found between the SP/AP ratio and the AP con-rar difference. Neither the SP/AP ratio in general nor the AP con-rar difference was correlated with the hearing level. However, enhanced values of the SP/AP ratio (0.35 or higher) were moderately correlated with the hearing level (r = 0.51), and their occurrence rate was 55.2%. An increased AP con-rar difference (0.13 ms or longer) was not correlated with the hearing level, and its occurrence rate was 50.2%; it appeared most frequently at stage 3 (p <0.05).


CONCLUSIONS
An enhanced SP/AP ratio might not always indicate the presence of endolymphatic hydrops associated with an increase in endolymphatic pressure. An increased AP con-rar difference might reflect the presence of a biased basilar membrane resulting from an increased endolymphatic pressure, and hence it is diagnostically essential to simultaneously evaluate the SP/AP ratio and the AP con-rar difference.
Ohashi
Toru
T
Department of Otorhinolaryngology, Hadano Red Cross Hospital, Hadano, Japan.
Nishino
Hirohito
H
Arai
Yoko
Y
Hyodo
Makoto
M
Takatsu
Mitsuharu
M
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D001300:Audiometry, Evoked Response / Q000295:instrumentation*; D001301:Audiometry, Pure-Tone; D016022:Case-Control Studies; D007758:Ear, Inner / Q000503:physiopathology; D004710:Endolymph / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology; D006801:Humans; D008575:Meniere Disease / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology*; D008875:Middle Aged; D011312:Pressure