Makoto Oda

Lesion site in sudden deafness: study with electrocochleography and transiently evoked otoacoustic emission.

We examined electrocochleogram (ECochG) and transiently evoked otoacoustic emission (TEOAE) on five cases of sudden sensorineural hearing loss which had no abnormalities detected on diagnostic imagings and showed complete recovery of hearing. At the initial examination, three cases showed a broadened wave 1 with prolonged latency in the auditory brainstem response (ABR) at 90 dB HL. The ECochG AP showed a broad waveform, low amplitude, and high threshold. CM threshold, although increased, was relatively well preserved compared with hearing threshold measured with conventional pure-tone audiometry. The thresholds in TEOAE examination were similar to those for CM and preserved better when compared with pure-tone audiometric thresholds. These findings suggest that the location of the disorder in these three cases involved not only the cochlea but also the retrocochlear auditory pathway. The other two cases showed normal ABR waveforms at 90 dB HL at the initial examinations. ECochG examination showed that a normal AP in one case and a smaller amplitude AP, an elevated threshold, and normal waveform of AP in the other ear. CM thresholds coincided with the conventional audiometry thresholds. These findings suggest that hearing loss in these two cases involved primarily the sensory hair cells.

Retrocochlear Deafness Examined by Electrocochleography and Evoked Otoacoustic Emission; A Case Report.

Using electrocochleography the evoked otoacoustic emission, we examined a patient with retrocochlear deafness which had been diagnosed by conventional audiometry.We used a transtympanic method to record AP (100 ms of 1ST), adapted AP (4 ms of 1ST) and CM. A needle electrode TN-92004 (Co. Unique Medical) was used to record the electrocochleogram and a probe N-1 (Co. Cortitone) to record the evoked otoacoustic emission.The patient was a 49-year-old female with bilateral sensori-neural hearing loss starting at age 13.Plain X-ray films did not show any abnormality. It was shown by the pure tone audiometry that 500 Hz dip and aging change without laterality. The SISI test, self-recording audiometry and speech discrimination tests showed retrocochlear deafness. The ABR recorded no response and there was no canal paresis or no other abnormal findings on ENG.The CM threshold was better than that obtained by conventional audiometry, and the CM amplitude was within normal limits. The AP threshold was much higher and the AP amplitude much lower than in normal subjects. The adapted AP amplitude was within normal limits.The best frequency of the evoked otoacoustic emission was 1kHz in both ears. The echo of otoacoustic emission was detected at-5 dBnHL in the right ear and at-10 dBnHL in the left ear. The evoked otoacoustic emission was normal.These results show that the region of her sensori-neural hearing loss is the spiral ganglion and/or cochlear nerve and that the organon spirale is intact.The electrocochleogram and the evoked otoacoustic emission were very useful in determining the region of sensori-neural hearing loss.

Assessment of Tinnitus Treatment.

As many previous authors have stated, there is no universally accepted classification of tinnitus, which seems to be due to various unknown mechanism. Because tinnitus can not be recorded electrophysiologically, it is generally assessed by psychophysical test such as pitch mathcing, loudness balancing and masking tests. Loudness is the most important psychological characteristic of tinnitus, but severity and annoyance are also factors. Loudness is assessed by the test mentioned above. Severity and annoyance are assessed by a severity scale graded according to the patients response to questions.A standard tinnitus assessment by the Tinnitus Workshop Group of the Japan Audiological Society and indivisual plans for tinnitus assessment proposed by clinicians are discussed. For clinical use, a scale classified into four or five grades seems to be extensively employed. In regard to the effectiveness of treatment of tinnitus, it is concluded that it should be judged at least four weeks after the completion of the proposed treatment.