Hideyo Asai

Diagnostic Value of Extratympanic Electrocochleography in Menière's Disease: Intérět diagnostique de l'électrocochléographie extratympanique dans la maladie de Menière

In order to examine the usefulness of the noninvasive extratympanic electrocochleography (ECochG) in the diagnosis of Menières disease, the results of extratympanic ECochG, performed on 28 normally hearing ears, 3 ears with otosclerosis and 325 ears with sensorineural hearing loss of various origins including 56 Menière ears, were analyzed. The characteristics of summating potential (SP) parameters in Menière ears were different from those of ears with hair cell loss due to streptomycin and kanamycin ototoxicity and noise, while there was no difference between the action potential (AP) of the cochlear nerve parameters of Menière ears and ears with hair cell loss. A much higher incidence of increased-SP/AP amplitude ratios in Menières disease was observed than in hearing loss of other origins. The results demonstrate the usefulness of noninvasive extratympanic ECochG in the diagnosis of Menières disease.

The effect of arginine-vasopressin and its analogues upon the endocochlear potential in the guinea pig.

The effect of arginine-vasopressin (AVP) and its analogues upon the endocochlear potential (EP) was examined in the guinea pig. AVP decreased the EP reversibly and dose-dependently like lysin-vasopressin (LVP). V1 antagonist failed to block the effect of AVP upon the EP. V2 agonist reversibly decreased the EP like AVP. The results suggest that V2 receptors mediate the action of vasopressin on the EP.

Hearing Recovery Following Large and Small Fenestra Stapes Surgery for Otosclerosis

Fifty-five ear of 49 patients with otosclerosis were operated on with either large fenestra stapes (stapedectomy; SDE) or small fenestra stapes (stapedectomy; STO) surgery. Pre-operative average hearing levels for the speech frequency ranges (0.5, 1, 2 kHz) were 56.1 dBHL for SDE and 61.0 dBHL for STO. These improved to 39.0 dBHL and 35.0 dBHL. Statistically, significant hearing recovery was obtained for a frequency range from 0.125 to 2 kHz for SDE and from 0.125 to 4 kHz for STO (p < 0.05, Dunnetts multiple variance test). The degree of post-operative hearing improvement for STO was significantly higher at 0.5, 2 and 8 kHz than that for SDE (p < 0.05, Students t-test). A pre-operative speech discrimination score of 80% was obtained at 68.9 dB for SDE and at 76.0 dB for STO. These values improved to 56.1 dB and 49.5 dB post-operatively. Thus, it was proved that STO results in better hearing than SDE does.

Comparison of summating potential in Menière's disease between trans- and extratympanic electrocochleography

The summating potential (SP) recorded concurrently with transtympanic (TT) and extratympanic (ET) electrocochleography in Menière ears was compared with respect to polarity and amplitude. There was a difference in SP polarity and amplitude between the two methods. The incidence of the increase in the ratio of -SP amplitude to the amplitude of the auditory nerve action potential (AP) (-SP/AP ratio) at 80 dB nHL as a response to a click was higher with the ET than with the TT method. Most of the ears exhibiting an increased +SP/AP ratio with the TT method showed an increased -SP/AP ratio with the ET method. The incidence of increased SP/AP ratios including -SP/AP and +SP/AP ratios was similar with both methods. A +SP was recorded in 14 of 25 ears upon stimulation with an 8-kHz tone burst with the TT method, whereas no +SP was recorded in 25 ears with the ET method. Tone bursts of 1 and 2 kHz produced a -SP and similar waveforms with both methods. Comparison of -SP amplitude recorded with both methods revealed that the ratio of -SP amplitude with both methods is different across the stimulus frequencies. The present study suggests that the -SP elicited by tone bursts of mid to low frequencies is more stable in the diagnosis of Menières disease than -SP elicited by a click because of the lesser influence of the electrode location and that the increase in the +SP recorded with the TT method may be of clinical significance in the diagnosis of Menières disease.

Clinical Application of Non-Invasive Electrocochleography

Non-invasive extratympanic electrocochleography (ECochG) was performed in normal-hearing subjects and patients with sensorineural deafness. Action potential (AP) threshold, N1 input-output function, waveform, summating potential (SP) are presented. AP thresholds were within 15 dB in normal-hearing ears and within 30 dB in hearing-impaired ears above subjective thresholds for the click. Correlational analysis showed that click-evoked AP thresholds are best correlated to pure tone thresholds at 2 to 4 kHz. Four types of N1 input-output functions were classified. Normal functions appeared in moderate high tone loss only at 8 kHz and low tone loss with almost normal threshold above at 4 kHz. Many ears with a flat loss had recruiting responses, while many ears with a high tone loss had either dissociated responses or responses with prolonged latency. Several types of waveforms were distinguished. Enhanced--SP was observed in Meniéres disease and late congenital syphilis to which endolymphatic hydrops is common. The clinical value of the non-invasive ECochG is discussed.

The Role of Summating Potential in the Diagnosis and Management of Meniere's Disease

To assess the role of a negative summating potential (-SP) in the clinical diagnosis and management of Menières disease, the relationship of -SP abnormality to clinical symptoms, hearing level and caloric test results was examined in 70 patients with unilateral Menieres disease. The click-induced -SP and action potential (AP) were recorded by extratympanic electrocochleography. When SP/AP ratio exceeded 0.43, the -SP was considered to be abnormal. No significant relationship was found between abnormal -SP and clinical symptoms (the duration of cochlear and vestibular symptoms, recent hearing fluctuation and recent vertigo attack). Ears with abnormal -SP had a significantly worse hearing loss at high frequencies (2-8 kHz) than ears with normal -SP, whereas there was no significant difference in hearing loss at low frequencies (0.25-1 kHz) between both ears. No significant relation was found between abnormal -SP and abnormal unilateral weakness in caloric test. The results indicate that the click-induced -SP reflects the pathophysiology of Menières disease basically in the cochlear partition at high frequencies.

Frequency Characteristics of Summating Potential in Ménière's Disease

SP iso-response functions in 9 patients with Menières disease were examined for differences in the properties between +SP and -SP. The iso-response functions of +SP and -SP exhibited a large difference. The iso-response function for +SP was centered at high frequencies (around 9 kHz in most cases) with fairly steep slopes on both sides towards both higher and lower frequencies, whereas -SP showed a low-pass function. The tendency was found for patients with normal hearing at high frequencies to have a larger Q10dB than patients with a hearing loss. The difference in properties between +SP and -SP suggests the possibility that +SP may provide different information on the pathophysiology of Ménières disease from that obtained from -SP.

The Relationship of SP and AP Findings to Hearing Level in Meniere's Disease

The relationship of summating potential (SP) and action potential (AP) to hearing threshold level was examined in 46 patients with a unilateral Ménières disease. The SP and AP were recorded with the extratympanic method. The ratio of -SP and AP amplitudes in affected ears to those in contralateral ears (-SP and AP amplitude ratio) at 80 dB nHL of click stimuli was used as parameters of analysis in order to diminish the variability of SP and AP amplitudes among individuals. The results revealed that there is no relationship between -SP amplitude ratio and the hearing threshold level at any frequency, whereas AP amplitude ratio has a significant negative correlation (r = -0.419, p less than 0.01) to the average hearing threshold level at 2-8 kHz, but not at 0.25-1 kHz (p greater than 0.05). The results indicate that an increase in the ratio of -SP amplitude to AP amplitude with the deterioration of the hearing at higher frequencies reported by our previous study (Mori et al., 1987) results from a decrease in AP amplitude rather than an increase in -SP amplitude. The dependence of AP amplitude on hearing threshold level and the independence of -SP amplitude on hearing threshold level suggests that the mechanism underlying the increase in -SP amplitude may be different from that causing the hearing loss in Ménières disease.

One-Stage Tympanoplasty and Mastoid Obliteration for Cholesteatoma Otitis Media.

One-stage tympanoplasty and mastoid obliteration for cholesteatoma otitis media was performed in 37 ears from November, 1988 through December, 1991. Twenty three received modified type III tympanoplasty for 17 attic type and 6 pars tensa type cholesteatomas, and 14 had modified type N tympanoplasty for 4 attic type and 10 pars tensa type cholesteatomas.A part of the posterior ear canal wall was removed for direct visualization of the cholesteatoma. After complete removal of the cholesteatoma, the mastoid cavity was obliterated with bone chips and cartilage, with bone chips, Palvas flap and cartilage, or with Palvas flap and cartilage. Postoperative hearing was good in 20/23 ears (87.0%) after modified type III tympanoplasty, and in 6/14 ears (42.9%) after modified type N tympanoplasty. Good results were obtained in 18/21 (85.7%) of those with attic type cholesteatomas and in 8/16 (50.0%) of those with pars tensa cholesteatomas. Cholesteatomas recurred in 0/23 ears (0%) after modified type III tympanoplasty and in 2/14 ears (14.3%, pars tensa type) after modified type IV tympanoplasty.These findings suggest that one-stage tympanoplasty and mastoid obliteration is useful, especially for attic type cholesteatomas.

Results of Stapes Surgery, 1980-1990.

Fifty five stapes operations performed during the past 11 years were studied. The average air conduction level of 0.5-2kHz was 58.5dBHL pre-operatively. This was improved to 31.6dBHL in audiograms recorded 3-6 months after operation. During the first 5 years of this survey, stapedectomy (SDE) was performed in 76.0% of the patients. Stapedotomy (STO) was more frequently done during the next 6 years (53.3%). A comparison of the two operations showed that hearing was better at all frequencies (0.125-8kHz) after STO than after SDE. The difference was greatest at 8kHz. It was confirmed that STO resulted in better hearing than SDE in patients with otosclerosis.