Early auditory evoked potentials (EAEPs) for the clinical diagnosis of otitis media in the rabbit.

The main objectives of the study presented here were to prove the early aud itory evoked potentials (EAEPs) as an objective procedure to confirm the di agnosis of otitis media in the rabbit. Therefore, in a clinical study the l atencies and amplitudes of the EAEPs of 67 (ear) healthy rabbits were deter mined at sound pressure levels (SPLs) of 80, 60 and 40 dB. In comparison, t he EAEPs of 9 rabbits with otitis media/interna were measured and the devia tion of the latencies and amplitudes statistically analysed. The rabbits (n o clinical signs of eardisease) showed at 80 dB SPLs the following latencie s: potential 0 appeared with 0,53 ms (= average latency, +/- 0,12 ms standa rd deviation), potential I with an average latency from 1,26 (+/- 0,13) ms, potential Il with 2,04 (+/- 0,14) ms, potential III with 2,71 (+/- 0,13) m s, potential IV with 3,72 (+/- 0,17) ms and potential V, which often was di fficult to recognize, had an average latency of 4,62 (+/- 0,30) ms. In comp arison to these results the rabbits with otitis media showed significant lo nger latencies at a sound pressure level of 80 dB for potential ii, III and IV. Altogether, all mean values of latencies were prolonged in the affecte d rabbits. The amplitudes of the potentials of the rabbits without clinical signs of eardisease had a broad mean variation with large individual diffe rences. The comparison of the results of EAEPs between rabbits with and wit hout otitis media showed some differences of the latencies but these differ ences were not obviously enough to confirm the diagnosis of otitis media. O verall, the results showed that EAEPs with only three different sound press ure levels give no convincing results, although extensively prolonged laten cies could lead suspicion on the diagnosis of otitis media. Further studies about the ascertainment of the objectively acoustic threshold in the rabbi t with otitis media are necessary. The comparison of the latencies and ampl itudes in the EAEPs between male and female rabbits showed longer latencies of potential III for male rabbits at 80 and 60 dB SPLs. Furthermore the re sults of latencies and amplitudes were compared between dwarf rabbits and o ther breeds. In dwarf rabbits (with an average body weight of 1420 g) signi ficant higher amplitudes for the potentials I, Il, IV and V were detectable than in other breeds (with an average body weight of 2852 g). This can be due to different body mass or different headsize.