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従来よりABRは幼小児の難聴の早期発見に多大な貢献を果たしてきた。 しかしABRは検査音としてclick音を用いているため聴覚の低音部の評価は困難である。 我々はABRで評価しにくい低音部0.5kHz-1kHzの幼小児の内耳機能の評価を主目的に外耳道誘導蝸電図を施行したのでその実態を報告する。 対象は10ヵ月-2歳6ヵ月の幼小児7名。 症例3は0.5kHzおよび1kHzにおいて70dBまでCMの反応が認められた。 他にもABRでたとえ反応が悪くても, 低音部のCMは残存していることが認められた。 小児にも侵襲の少ない外耳道誘導蝸電図を利用することで幼小児の内耳機能を他覚的に評価することが可能であると推測された。 幼小児難聴の限られた残存聴力を活用, そして保護するためにも, このCMからの情報は補聴器のフィッティングに有効であると考えられた。

過去10年間に長崎大学耳鼻咽喉科を受診し, 蝸電図あるいは聴性脳幹反応Auditory Brainstem Response (ABR) を施行して詐聴と診断し得た82名について検討を行った。 昭和54-58年の前期5年間と昭和59-63年の後期5年間を比較すると, 症例数は約2倍, 当科にて蝸電図またはABRを行った全症例に対する比も約1.5倍と増加しており, 70歳以上の高齢者症例も増加していた。

最初メニエール病と診断されたが, その後の臨床経過から椎骨脳底動脈循環不全 (VBI) によるメニエール病様症状と判明した2症例を報告した。 症例1は47歳の女性で, 椎骨動脈造影 (VAG) では異常は指摘できなかったが, 患側の三叉神経障害を認めた。 また, 純音聴力検査及び蝸牛マイクロフォン電位 (CM) 検出域値の著明な改善が見られ, VBIによる内耳血管条のanoxiaが原因と考えた。 症例2は53歳の男性で, 患側半身の知覚鈍麻, VAGにて健側の椎骨動脈の高度狭窄を認めた。 また, 蝸電図検査では, 純音聴力域値よりも良好なCM検出域値, 幅の広いAPの所見から, VBIによる蝸牛神経障害と考えた。

The effect of the changes of interstimulus interval (ISI) was compared among the four groups consiting of normal hearing subjects sensorineural deafness due to hair cells damage, due to endolymphatic hydrops and cerebello-pontine angle lesion.The click sound stimulation was used for measurement of the auditory whole nerve action potential (AP), using the transtympanic technique in electrocochleography.A moderate decrease in similar manner was shown in two groups of normal hearing subjects and sensorineural hearing loss with hair cells damage. On the other hand, a remarkable decrease was shown in order two groups of sensorineural hearing loss with endolymphatic hydrops and with cerebello-pontine angle lesion.It is suggested that a remarkable decrease in amplitude of AP with shortening of ISI is due to abnormal function in synaptic junction between the cochlear hair cell and the first auditory neuron and/or abnormal function in the post synaps.

A 45-year-old house wife with hemifacial spasm developed a profound sensorineural deafness after neuro-vascular decompression operation of the facial nerve at cerebellopontine angle.Electrocochleography was performed using the transtympanic electrode technique.The results obtained were as follows:The wave form of action potential (AP) showed a broad pattern and a low amplitude, but AP threshold was remarkably lower than that of pure tone audiogram.The cochlear microphonics showed the well-developed responses.The above findings seem to indicate that the organ of Corti was found to be functioning because of the preservation of blood supply, but the first neuron region or spiral ganglion cell region was impaired partially and retrogradely, by the surgical procedure on the eighth cranial nerve.

AP and SP responses were investigated by the single electrode technique.The recording sites were the round window, mid-portion of the bony wall of cochlea, the apical portion of the cochlea and bony wall of the hypotympanum.One cycle of sound stimuli at 8kHz, 4kHz, 1kHz and 0.5kHz was used and the sounds were given from 50cm lateral to the tested ear.The tone bursts with duration of 30msec were used as measurement of SP.The results obtained were as follows:The highest value of AP out-put potential was obtained by the round window recording. The highest value of AP out-put potential was obtained by the stimulation of one cycle of 4kHz and 8kHz.The positive SP as seen in the round window recording changed to a decreased positive SP or negative SP at the recording sites except the round window.The SP induced by a tone burst from the round window showed the positive SP at high frequency and the negative SP at low frequency.These results will contribute to the research on the single electrode recording of AP and SP responses in these animals.

The cases with low tone sensorineural deafness were studied using the transtympanic-electrode technique of electrocochleography.The results obtained were as follows:1) Low tone sensorineural deafness of sudden onset without vertigo:All the cases showed high AP and -SP amplitude and satisfactory CM response. These findings resembled the electrocochleographic findings of type I of Meniere's disease suggesting of the relationship with endolymphatic hydrops. The hearing returned to normal range in a half of the cases but remained hardly changed in the other half. The difference between these two groups could not be clarified electrocochleographically.2) Familial progressive deafness showed low tone sensorineural deafness:This case showed a high threshold and a low amplitude of CM at low frequency, and showed cochlear hair cell damage at low frequency range.3) Low tone sensorineural deafness due to retrolabyrinthine lesion:This case showed a normal CM but a low AP amplitude, and lacked a rapid increase of AP amplitude with increasing click intensity in the intensity region of AP input-output functions.

Cochlear microphonics (CM) and action potential (AP) were measured in animals in which labyrinths were damaged by injection of the various kinds of solution into the facial nerve through the stylomastoid foramen.The results obtained were as follows:1) After the injection of tetracycline and hydrochloride, the CM and AP waves were not recorded, even applying the maximal sound stimulus.2) After the first injection of antigen into the sensitized rabbits, CM amplitude was markedly increased at 4KHz, while increased slightly at 0.5KHz.After the repeated injections, caloric response was reduced and the CM and AP amplitude decreased or did not show response to the sound stimuli of the 20dB above VDL in both frequencies.The CM and AP amplitude, however, recovered to the same threshold as before the first injection limits 24 hours after the first procedure.Histopathological findings of the organ of Corti after the injection of tetracycline and hydrochloride revealed degeneration, but no remarkable change was seen in immunologically treated cases.It is thought that these electrophysioiogical phenomena induced by the injection of antigen into sensitized animals were resulted from the antigen-antibody reactions in the autonomic nerve and microcirculations in the cochlea.

Electrocochleography was performed on six patients with posterior cranial Fossa tumors which consist of three cases of acoustic neurinoma of grade II-III, a case of glioblastoma multiforme originating from cerebello-superior pons, a case of astrocytoma of grade III originating from medulla oblongata-inferior pons, and a case of meningioma originating from Meckel's cavity. Recording was made with the use of the transtympanic needle technique. AP input-output functions with acoustic neurinoma were very similar to those obtained in patients with sensorineural hearing loss showing the phenomenon of recruitment. In AP responses recorded from the patients with cerebello-superior pontine tumor and Meckel's cavity tumor, a loss of the positive portion of the potentials (P1) was characteristic. This phenomenon may be due to the compression on the auditory nerve by the growing tumor. The polarity of SP in all cases showed negative deflection without abnormal increment. CM responeses recorded from the patients were the same as in a normal subject. In the cases presented, although the abnormal changes in input-output functions as well as the changes in the wave form patterns of AP responses revealed a lesion of the portions corresponding to the sensory and/or to the neural structure, the presence of a well-developed CM may be explained by the fact that the hair cells remain unaffected. Therefore, it is thought that simultaneous recording of CM and AP gives great promise as a means of differential diagnosis between neural and cochlear pathology.

The purpose of this investigation is to study the site of lesions in mumps deafness by Electrocochleography.Sixteen affected ears of fifteen patients ranging in age from four to fourty-two with the average being 15.5 were investigated. Recording was made in an electrically shielded sound proof room with the use of the transtympanic needle electrode technique. Clicks for measurement of auditory nerve action potential (AP) and short tone-bursts for cochlear microphonics (CM) were used as sound stimuli.Although the audiometric examination in all cases confirmed no response, the following three categories of cochlear pathophysiological features in mumps deafness can be classified according to CM responses.1) No AP response and the well-developed CM response: It seemed to indicate that the neural regions related to the source of AP response were impaired, but the organ of Corti was found to be functioning because the recorded CM responses were the same as in a normal hearing subject.2) Neither AP nor CM response: It seemed to indicate that both the neural and the organ of Corti were impaired severely.3) No AP response and the decreased CM responses: It seemed to indicate that the neural regions were impaired severely, but the organ of Corti were impaired only partially.

Pathophysiology and prognosis of hearing acuity in 16 ears of 10 cases with inner ear syphilis were studied by the transtympanic electrode technique of electrocochleography.The results were obtained as follows:The improvement of hearing acuity after steroid therapy was obtained at low frequency range on audiogram. These cases showed a well defined AP, a dominant-SP and remarkable CM response at 0.5kHz. It was speculated that there may be endolymphatic hydrops and the reversible change of hair cells at low frequency area of the cochlea.On the other hand, in the cases showing slight improvement of hearing acuity, both AP and CM responses shwed a low out-put potential which suggests a reversible change or organic damage of the hair cells or cochlear nevre.

A comparative study was made on electrocochleography by the transtympanic and the ear canal recording technique in normal hearing subjects.The results obtained were as follows:The auditory whole nerve action potential (AP) recorded from the ear canal showed extremely low ampliitude but AP latency, wave form and threshold did not so differ significantly from the transtympanic recording technique.Cochlear microphonics (CM) recorded from the ear canal also showed a low output potential as well as AP. Furthermore, there was a limitation of information from the cochlea because of a higher detection threshold of the CM and mixture of the electromagnetic induction wave, Therefore, the transtympanic recording technique is more efficient than that of the ear canal recording technique.

さまざまな時期に蝸電図検査をした突発性難聴患者168名を, 検査日別に5群にわけて, CM検出域値と純音聴力 (蝸電図検査時と聴力固定時) との関係を周波数別に検討した。 早期より, どの周波数においても検査時純音聴力とは関係なく, CM検出域値に応じて聴力の改善がみられた。 CM反応からみた突発性難聴の病態は, 主としてらせん器周辺の障害と考えられた。 固定時聴力を決める不可逆性CM発生機構障害 (主に有毛細胞と考える) と聴力改善の可能性を示す可逆性刺激伝達ブロック (シナプス-聴神経) の両者が種々の割合で存在し, このらせん器周辺の障害の程度により, 特に発症時のCM発生機構の障害の程度により, 予後がほとんど決ってしまうと考えられた。 CM反応をみることにより早期より予後を推定することが可能である。

The authors observed eight cases of intermittent tinnitus which appeared during the course of recovery from peripheral facial nerve paralysis of various etiology. The tinnitus occurred whenever a certain mimic facial muscle contracted voluntarily or involuntarily.As the tinnitus in each case didn't dispaaeared by medical treatment or other conservative therapy, tympanotomy via extenal auditory meatus was made. Under the operating microscope, contraction of the stapedius muscle synchronous with contraction of the mimic facial muscle was observed. The tinnitus had disappeared completely immediately after the tendon of stapedius muscle was sectioned. Thus the existence of tinnitus due to abnormal contraction of stapedius muscle was confirmed.Further, tinnitus in each cases was considered to be an expression of abnormal associated movement involving the stapedius muscle during the course of the recovery from facicl nerve paralysis.Changes of the minimum audible. threshold (air conduction) were measured in each case during the stapedius muscle contracted without sound stimulation, and the results showed a good accordance to the results obtaind from the theoretical and experimental works which had been reported by several authors.In a conclusion, the authors stressed the importance of the stapedius muscle tinnitus in the study of pathogenesis of tinnitus, facial nerve paralysis, as well as in the study of middle ear function.