Mediterr J Otol 2006:2(1): 14-18

Estimation of traveling wave delay of the basilar membrane using frequency-specific electrocochleaography: Methodology and normative data 

Bulent Satar, Altan Yildirim, Serdar Karahatay, Deniz Şen 

Department of Otolaryngology–Head and Neck Surgery, Gülhane Military Medical Faculty,  Ankara, Turkey  bulentsatar@yahoo.com

Objective: The aim of the study was to estimate traveling wave delay of the basilar membrane using transtympanic electrocochleography in healthy subjects without hearing loss or vestibular disorders.

Subjects and methods: Sixteen ears in 10 healthy volunteers were tested with transtympanic electrocochleography, using a monopolar needle electrode. They had no vertigo or dizziness and had pure tone thresholds of ≤20 dB nHL at the frequency range of 0.250 to 6 kHz. A series of 2-8-2 tonal stimuli (19.7/sec) at 0.5, 1, 2, and 4 kHz, each at 90 dB nHL, were delivered. Latency of the action potential was measured across the frequency range. Latency difference was then calculated by subtracting action potential latency measured for 1 specific frequency from another. The latency difference was used as a measure of traveling wave delay.

Results: Action potential latency was 4.03, 3.5, 3.05, and 2.8 msec at 0.5, 1, 2, and 4 kHz, respectively. We noted that traveling wave delay showed a tendency to decrease toward the basal turn of the cochlea, which means that traveling wave velocity is higher at the basal turn of the cochlea compared with the apical turn. The traveling wave delay estimate obtained in this study is consistent with data extracted from the literature.

Conclusion: The study indicated that traveling wave delay could be estimated using transtympanic electrocochleography. With this technique, the wave resolution is very good, thereby making identification of the response peak easier. No additional hardware is required for signal processing unlike with the derived band technique. Further study with  patient groups is warranted.