J. Haapaniemi et al., Transtympanic versus tympanic membrane electrocochleography in examining cochleovestibular disorders, ACT OTO-LAR, 2000, pp. 127-129
The use of electrocochleography (EcoG) is considered to be of clinical valu
e in otological diagnosis. Non-invasive ear canal (EC) and tympanic membran
e (TM) EcoG recording techniques, and invasive transtympanic (TT) technique
are the methods used for objective assessment of cochlear function. In thi
s study, eight adults (16 ears) with suspected Meniere's disease were exami
ned using a newly designed, disposable tympanic electrode and a traditional
, thin transtympanic needle. The amplitudes of the TT electrode responses w
ere 4-6-fold larger than those produced by the TM electrode. The morphology
of the waveforms for the two recording techniques was nearly identical. Th
e mean amplitudes of the action potential (AP) obtained with the TM electro
de were 2.39-3.73 mu V, and with the TT electrode 14.08-19.60 mu V, dependi
ng on the stimulus intensity. For the summating potential (SP), the TM and
TT electrodes had mean amplitudes of 0.82-1.60 mu V and 3.53-5.81 mu V, res
pectively. The SP/AP ratios were larger with the TM electrode than with the
TT electrode. They were inconsistent in four ears (25%) when measured with
the TM and TT electrodes. All patients were more satisfied with the TT exa
mination, since it was quite painless, unlike the TM examination. The autho
rs recommend the use of the TT recording technique as a painless examinatio
n in which the electrode is close to the inner ear, allowing a good signal-
to-noise ratio and large amplitudes. Diagnostic interpretations art: easier
and more reliable with the TT electrode than with the TM electrode.