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Recently, acute low-tone senseorineural hearing loss (ALHL) has become common, and its good prognosis is known well. On the other hand, several reports have suggested that ALHL is frequently associated with Meniere's disease. We retrospectively examined the clinical course of 357 cases that were diagnosed and treated as ALHL at our hospitals. Forty-four of these cases that showed high-tone hearing loss in association with age-related changes were classified as atypical cases. The clinical futures of 49 "poor prognosis cases", who experienced recurrent hearing loss and/or profound hearing loss, are reported. Eight of the 49 cases who experienced recurrences had progressive hearing loss upto middle or high tones. Seventeen cases complained of vertiginous sensation, and 8 of these cases experienced recurrent attacks of vertigo and were diagnosed as having Meniere's disease. The former seventeen cases accounted for 34.7% of the "poor prognosis cases", and the latter eight accounted for 16.3% of these cases. Our results suggest that the hearing loss is more frequently associated with Meniere's disease in cases who experience recurrent hearing loss. Thus, cases initially diagnosed as ALHL may include some cases of progressive hearing loss and Meniere's disease. Even in cases in which hearing improvement is obtained, careful clinical observation is necessary, especially in older patients with bilateral affliction and atypical presentation. ALHL has been generally considered to have a good prognosis, however our examination revealed a relatively high frequency of recurrences, progressive hearing loss and complication by vertigo. We recommend, based on this evidence, that careful explanation of this disease is necessary at time of initial informed consent.

We treated 33 cases of intractable Meniere's disease with endolymphatic sac drainage and steroid-instillation surgery (EDSS), attaining good long-term results in vertigo and hearing. To elucidate how EDSS affects the diseased inner ear, we examined changes in plasma inner ear hormones after EDSS. Among inner ear hormones, plasma vasopressin was significantly decreased after EDSS compared to after mastoidectomy. In cases with good long-term results in vertigo and hearing, postoperative plasma vasopressin remained lower over the long term than in cases with poor results. In cases with negative glycerol test results one year after surgery, postoperative plasma vasopressin also remained significantly lower over the long term than in cases with positive results. Previous studies reported that vestibular neurons projected into hypothalamic supraoptic and paraventricular nuclei and that changes in the inner ear pressure were related to plasma vasopressin. Taken together with present findings, this suggests that EDSS may reduce plasma vasopressin through modification of the diseased inner ear environment, resulting in improved inner ear function.

Endolymphatic sac surgery is one of the most widely accepted techniques used to treat intractable Meniere's disease. To improve this surgery, we developed the following techniques: A simple mastoidectomy was used to expose the endolymphatic sac between the sigmoid sinus and inferior margin of the posterior semicircular canal. The sac was opened and filled with a mass of prednisolone. A bundle of absorbable gelatin films was then inserted into the sac lumen to expand it, followed by gelatin sponges dipped in a high concentration of dexamethasone. Long-term results (17-32 months) in 20 patients with intractable Meniere's disease treated with endolymphatic sac drainage and steroid-insertion surgery (EDSS) showed that definitive spells were completely controlled in 15 of 20 cases (75%); all reports of vertigo decreased; hearing improved in 12 of 20 cases (60%); and annoyance due to tinnitus decreased in 15 of 20 cases (75%). Steroids directly instilled into the endolymphatic cavity may thus be more effective with the diseased inner ear organs than those applied via any other route. Draining of endolymphatic fluid at the sac into the mastoid cavity also contributed to these satisfactory EDSS results.

Understanding the appearance of vestibular symptoms during periods of convalescence after surgery for the treatment of Meniere's disease is important for determining when a patient can return to work as well as the long-term results of the operation. We have treated 20 cases of intractable Meniere's disease with endolymphatic sac drainage & steroid-instillation surgery (EDSS) [Kitahara T, et al., Ann Otol Rhlnol Laryngol in press, 2000] and observed the subjective symptoms and objective vestibular findings using electronystagmogram (ENG) during the subsequent period of convalescence. The average postoperative durations of subjective static and evoked vestibular symptoms were 1.7 and 6.7 days, respectively. Those of spontaneous, positional and positioning nystagmus observed using ENG were 1.2, 2.0 and 7.9 days, respectively. In cases with a long history of Meniere's disease, postoperative static vestibular sensation and positional nystagmus lasted significantly longer than in cases with short histories. In cases with poorly developed temporal bony pneumatization in the area behind the posterior semicircular canal, postoperative evoked vestibular sensations and positioning nystagmus lasted significantly longer than in cases with well developed temporal bony pneumatization. Vestibular symptoms resulting from direct invasion during EDSS were considered to be slighter than those resulting from vestibular neurectomy or gentamicin treatment and almost the same as those resulting from endolymphatic sac surgery.

The purposes of this study were to evaluate the effect of inflating the Eustachian tube in patients with tinnitus, and to identify diseases in which tubal inflation is indicated. Fifty-four ears of as many patients complaining of tinnitus were examined by pure tone audiometry and decreases in pitch and loudness associated with tinnitus were also evaluated by tinnitus audiometry (Danac-100, DanaJapan). Tinnitus was associated with sensorineural hearing loss (SNHL) in 44 ears and not associated in the remaining 10. The subjects were classified further into two groups: the higher tone group showed a pitch range with tinnitus of 1000 Hz or higher, and the lower tone group showed a pitch range of less than 1000 Hz. In the higher tone tinnitus group with SNLH, the tubal inflation was effective in 3 of 31 ears (10%), and in the lower tone group, 10 of 13 ears (77%). On the other hand, in the tinnitus group with no hearing loss, the method relieved tinnitus in 6 of 10 ears (60%). In the higher tone tinnitus group with no hearing loss, the tubal inflation was effective in 3 of 6 ears (50%), and in the lower tone group, 3 of 4 ears (75%). In this study, however, no ears were permanently relieved of tinnitus with tubal inflation. In the higher tone group, the duration of the reduced tinnitus was less than 10 minutes. In 69% of the lower tone group, the reduction was from 20 minutes to 2 hours. The effect did not continue for more than 2 hours at the longest. In conclusion, Eustachian tubal inflation is indicated in diseases with tinnitus as follows: 1. Lower tone tinnitus with SNHL, particularly in Meniere's disease and acute onset low-tone type SNHL, may be temporarily relieved with tubal inflation. 2. Tinnitus in an ear without SNHL that may gain transitory relief from ringing with the tubal inflation.

It is now well documented that in cases of Meniere's disease/endolymphatic hydrops, the electrocochleography (ECochG) evoked by a broad-band click is often characterized by an enlarged summating potential (enlarged-SP) and a large negative summating potential to action potential ratio (large -SP/AP) but these mechanism have not been clarified. The aim of this study was to find clues to the mechanism of enhanced -SP and large -SP/AP in Meniere's disease, by using long-tone burst stimuli. We also sought to determine the significance of SP measurement for evaluating the cochlear function in Meniere's disease/endolymphatic hydrops. ECochG was performed on 29 ears of patients with Meniere's disease and 12 ears of adults with normal hearing as a control group. Extratympanic ECochG was carried out using an HN-7 electrode. The sound intensity used for measuring the SP and SP/AP was 90dBnHL. Both SP and AP were elicited by clicks and long-tone bursts of 50 ms duration with a 1-ms rise-fall time. The clicks and long-tone bursts with frequencies of 0.5, 1, 2, and 4 kHz were delivered by the tubal transducer (NC-3). In most of the patients with Meniere's disease, SP evoked by the long tone burst stimuli showed negative polarity (-SP) at each frequency. Analysis of variance (X2test) indicated a significant difference in -SP at 0.5 and 1 kHz between Meniere's disease and the control group (0.5 kHz: p < 0.001, 1 kHz: p < 0.02). When setting the normal upper limit of the -SP/AP to 0.4, we found that the number of cases over 0.4 which showed -SP at 0.5 and 1 kHz was much larger than those below 0.4 in the 29 ears of patients with Meniere's disease. There was no difference between the types of Meniere's disease or glycerol test and SP polarity elicited by long-tone burst stimuli. The enhanced -SP and large -SP/AP obtained by the broad band clicks seem to reflect a component of negative SP polarity in the low and middle frequency ranges. It was assumed that the reverse phenomena of SP polarity in the low and middle frequency ranges were related to changes in hydrodynamic characteristics in the upper cochlear turns due to abnormal endolymphatic pressure. Our findings suggest that SP recording by long-tone burst stimuli is useful in detecting changes in cochlear partition due to abnormal intracochlear pressure, most likely in the early phase of Meniere's disease based on the wide frequency information of SP.

Extratympanic electrocochleography and pure-tone audiometry were performed in unilateral Ménière's disease patients before and 1, 2 and 3 hours after oral administration of glycerol. The mean electrocochleographic response from 12 recordings at 80 dBnHL click stimuli was determined to obtain stable values. The electrocochleographic response during the glycerol dehydration test was compared with that in normal subjects (28 ears). A positive result on a pure-tone audiogram was determined by an improvement of at least 10 dB in two octave bands. In 25 involved ears with Ménière's disease, the action potential (AP) amplitudes gradually decreased during the test, but there were no significant differences. The summating potential (SP) amplitudes decreased during the test and there was a significant difference at 2 hours after administration. The negative SP/AP ratios were unchanged. The Ménière's disease patients were classified into two groups; one with a positive response on the audiogram and the other negative responses including deterioration. According to multiple comparison testing, there were significant differences in AP amplitudes and SP amplitudes between the positive group and normal controls at 2 and 3 hours after administration, and between the positive group and the negative group at 3 hours. Electrocochleographic changes in the positive audiogram group were significant. Then, the patients were classified into three groups by negative SP/AP ratio before administration. The first group consisted of negative ears whose negative SP/AP ratios were less than 0.36, which was the upper 95% confidence limit for 40 normal hearing ears, the second consisted of slightly positive ears (0.36or = negative SP/AP ratio0.40), the last consisted of severely positive ears whose ratios were more than 0.4, which was the upper 99% confidence limit. There was a significant difference for the SP amplitudes between the slightly positive group and normal controls at 2 hours after administration. Electrocochleographic changes in the slightly positive group with a negative SP/AP ratio were significant at this SP amplitude. In 18 normal ears with Ménière's disease, electrocochleographic changes showed no significant difference. However, the SP amplitudes in 3 ears and the negative SP/AP ratios in 4 ears decreased to less than 80% of the pre-administration value, although they had not fallen below that in the normal controls. These decreases indicate that some normal ears with Ménière's disease already had the distinctive features of involved ears. Whether the fluctuation in hearing will appear in the normal ears with decreasing SP amplitudes or negative SP/AP ratios, as in the involved ears, remains to be determined.

In order to detect vestibular endolymphatic hydrops, the directional preponderance of the VOR gain (VOR-DP%) during sinusoidal rotation (freq. 0.1Hz; Amp. 120deg) was calculated and compared between pre- and post-intravenous injections of furosemide (20mg). Abnormal changes in VOR-DP% (> = 10%) from the pre-injection level were referred to as positive in this furosemide VOR test (FVOR). The following results were obtained from this study. (1) Positive responses were obtained in 31 of 61 (51%) patients with definite Meniere's disease, in 11 of 21 (52%) patients with delayed endolymphatic hydrops and in 7 of 10 (70%) with syphilitic labyrinthitis. In contrast, the majority of patients responded negatively with sudden deafness or other peripheral vestibular disorders. (2) Following the endolymphatic shunt operation, in 2 out of 3 patients (67%) in whom vertiginous attacks had been decreased or disappeared after the operation results changed from positive to negative. (3) The positive rate in Meniere's disease was dependent on the frequency of the vertiginous attacks before the test or the duration from the last attack to the test. (4) Combined with the glycerol dehydration test or electrocochleography, the FVOR test could detect endolymphatic hydrops of Meniere's disease at a high positive rate. (5) There were no side-effects of the furosemide on the inner ear, such as deterioration of hearing acuity or tinnitus. In conclusion, the FVOR test is useful for detecting and following up fluctuating vestibular endolymphatic hydrops, which occur in disorders such as Meniere's disease, delayed endolymphatic hydrops and syphilitic labyrinthitis.

Autonomic nervous function in 68 vertiginous patients and 33 controls was studied using power spectral analysis of heart rate variability. First, a system was developed which computes the power spectral density (PSD) of beat-to-beat heart intervals using a continuous non-invasive finger blood pressure recording obtained with the FINAPRESS device. A fast-Fourier transform algorithm was used to compute the PSD. In frequencies up to 0.5 Hz, the PSD of heart rate variability contains three major components: a low frequency (P1), a middle frequency (P2) and a high frequency (P3). Each component was normalized by dividing the absolute values by total power (T), and then used as an index of each component. Second, the effects of passive tilt, respiratory frequency and specific pharmacological sympathetic or parasympathetic blockade on the indices of these components were evaluated in the control group. The following results were obtained. 1. During passive tilt, the normalized power of P2 was increased, whereas that of P3 was decreased. 2. The peak frequency of P3 was consistent with the frequency of respiration. 3. Sympathetic blockade decreased the normalized power of P2, whereas parasympathetic blockade decreased the normalized power of P3. From these results, I concluded that the normalized power of P2 and P3 are quantitative markers of sympathetic and vagal nervous activities, respectively. Third, the results of spectral analysis in patients were compared with those in controls. The following characteristics of autonomic nervous function in vertiginous patients were noted. 1. The normalized power of P3 in patients was lower than that in controls, suggesting that parasympathetic nervous activity at rest was suppressed in patients. 2. The increase of normalized power of P2 with passive tilt was suppressed in patients, suggesting suppression of sympathetic response to passive tilt. 3. In patients with Meniere's disease, during the active period of vertigo attacks, the normalized power of P2, which is an index of sympathetic activity, was higher than that in the intervals between vertigo attacks. Fourth, with caloric stimulation in the control group, an increase of the normalized power of P2 was observed during or after the stimulation, which suggests that vestibular stimulation increases sympathetic activity. I therefore suggest the following: 1. Decreased parasympathetic activity and suppression of sympathetic response were present in the vertiginous patients. 2. Sympathetic activity was increased by vertigo attacks in the patients with Meniere's disease.

Among 80 patients with low tone sudden deafness (LTSD) who visited our department over the past 15 years, there were 6 cases (7.5%) who subsequently progressed to Menière's disease. The clinical and audiological processes of the 6 patients were studied in detail and the following results were obtained. (1) In these 6 patients, the time between onset of LTSD and the diagnosis of Menière's disease ranged from 4 months at the shortest to 6 years and 8 months at the longest, 2 years and 9 months on average. (2) Two pattern types were seen in the change from LTSD to Menière's disease: changing within a short period of time after recurrence of an LTSD-like attack, and changing after more than one year without recurrent attack. (3) The monoattack-nonrecovered type of LTSD and the recurrent type of LTSD within three months after the onset (short-term prognosis) frequently progressed to Menière's disease. (4) There were no close relationships between subjective symptoms and audiological features in the pre-Menière's disease period (from the onset of LTSD to the recurrence of vertigo with cochlear symptoms). (5) The 6 patients showed various audiogram shapes at the time of progression to Meniere's disease; 3 cases with the slightly rising type, 1 with the high frequency-impaired type, and 2 with the moderate, gradual and flat type. (6) Of the 6 patients, 3 had good hearing during long term observation. At least 2 patients seemed to have the mild type of Menière's disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Recently Meniere's disease is believed to show a pathological features of endolymphatic hydrops, but the etiology of this disease has not yet been ascertained. Many investigators tried to create animal models with endolymphatic hydrops by obliterating endolymphatic sac and duct. However, these methods have not been adequate to explain the mechanism of development of Meniere's disease, because it gives mechanical damage to destroy endolymphatic sac and duct. On the other hand, Meniere's disease is thought to develop even as a result of stress. The present paper reported the conduction of an acute experiment, creating active endolymphatic hydrops by stress load, to study the occurrence rate of endolymphatic hydrops and the pathological findings of inner ears by a light microscope. This was followed by a light and electron microscopic study on the changes in permeability of the cochlear lateral wall with horseradish peroxidase and a study of the development mechanism of endolymphatic hydrops. Results obtained were as follows: 1. Although it was impossible to cause endolymphatic hydrops with a single stimulation, four kinds of stress stimulations could cause endolymphatic hydrops with the rate of 37.8%. 2. Judging from the different pathological findings between the group with four kinds of stress stimulations and the untreated control group, vessel permeability in the stria vascularis was highly changeable, while that in the spiral ligament was not. 3. It was found out that increased permeability of the stria vascularis vessels was by increased pinocytotic vesicular transport and through tight junctions from vessel lumen to basal lamina and that it was presumably only by increased pinocytotic vesicular transport beyond basal lamina. 4. It was assumed that increased permeability of the stria vascularis vessels was one of the causes of endolymphatic hydrops which were believed to be pathological features of Meniere's disease.

Transtympanic electrocochleography (ECochG) was performed on 137 definite Meniere ears, 29 normal ears and 383 ears with other diseases. The average SP/AP amplitude ratio (SP/AP) was significantly larger than that of normal subjects in the following four disease groups whose causes are thought to be endolymphatic hydrops: 1) definite Meniere's disease, 2) suspected Meniere's disease, 3) delayed endolymphatic hydrops and 4) labyrinthine syphilis. The SP amplitude could not provide any information for a differential diagnosis of endolymphatic hydrops from normal subjects nor from other sensorineural deafness . The upper 99% confidence limit of normal SP/AP using a 100dBSPL click was 0.37 for 29 subjects. In patients with Meniere's disease the relationship between SP/AP and clinical data such as pure tone threshold, audiogram pattern, results of glycerol test and duration of illness from the first vertiginous attack to the test were investigated. In patients with severe hearing loss, the number of those showing SP/AP of greater than 0.37 was much higher than in patients with less severe hearing loss. There were no relationship, however, between SP/AP and duration of illness, or audiogram pattern, or glycerol test. ECochG was recorded before and after intravenous administration of 50 gr of glycerol (10% solution, 500ml), and a significant decrease of SP/AP was found in 21 Meniere ears. However, there were no change of SP/AP after oral administration of 50 gr of glycerol (50% solution, 100ml) and isosorbide (70% solution, 2.0gr/kg of body weight). After endolymphatic sac surgery a decrease of SP/AP of 10% or more was found in 5 ears, an increase of SP/AP in 3 ears, and no change of SP/AP in 3 ears. In the patients showing no change of SP/AP after the surgery, numerical values of vertigo by AAOHNS were higher than in patients showing an increase or a decrease of SP/AP. The results demonstrate the usefulness of ECochG in diagnosis of endolymphatic hydrops and indicate a possibility of monitoring the state of hydrops after administration of glycerol and endolymphatic sac surgery.