A clinical study of electrocochleography in Menière's disease

Cervical Vestibular Evoked Myogenic Potentials That Are Absent at 500 Hz But Present at 1000 Hz Are Characteristic of Endolymphatic Hydrops-Related Disease

OBJECTIVES

It remains unclear whether the dominance of 1000 Hz responses over responses at 500 Hz in cervical vestibular evoked myogenic potentials (cVEMPs) are characteristic of endolymphatic hydrops (EH), due to the presence of patients with absent responses at both frequencies. The purpose of the present study is to examine whether the dominant cVEMP responses at 1000 Hz over 500 Hz are characteristic findings of EH-related diseases among patients who show various cVEMP findings.

DESIGN

We retrospectively reviewed the medical records of 470 consecutive patients who underwent cVEMP testing with short-tone bursts at both 500 Hz and 1000 Hz. We categorized the cVEMP responses of these 470 patients into the following five groups: (group 1) present responses at both frequencies bilaterally, (group 2) present responses at 500 Hz but absent at 1000 Hz on at least one side, (group 3) absent responses at 500 Hz but present at 1000 Hz on at least one side, (group 4) absent responses at both frequencies on one side and present at both frequencies on the other side, and (group 5) absent responses at both frequencies bilaterally. We compared the proportion of EH-related diseases between each group and the other four groups and then investigated any increased or decreased disease incidence in each group.

RESULTS

In group 3, the proportion of EH-related disease was significantly higher (p < 0.01), and the incidence of an EH-related disease was greatly increased (standard residual value > 3).

CONCLUSIONS

cVEMPs that are absent at 500 Hz and present at 1000 Hz may be characteristic of EH-related disease.

Tone Burst Electrocochleography for the Diagnosis of Clinically Certain Meniere's Disease

The technique of transtympanic electrocochleography was initially developed as an objective hearing threshold test by Eggermont. Gibson et al. (1977) claimed that an enlarged direct current component of the action potential (AP) called the summating potential (SP) is an indication of endolymphatic hydrops, later confirmed by Coates who proposed an SP/AP ratio measure. This led to numerous publications using diagnostic ratios of 0.33-0.35. The insensitivity led to an eventual disenchantment with the test as a reliable objective test for Meniere's disease. It was further confused by audiologists employing remote canal or ear drum electrodes which give a response about one-fourth of the magnitude obtained by an electrode in contact with the cochlea. Subsequently Gibson stated that an SP/AP ratio of <0.5 is not diagnostic for hydrops. He then showed that a tone burst stimulus gave the test a significantly higher sensitivity and specificity, which has been supported by others. On MRI inner ear imaging with gadolinium hydrops can be seen, but the quality of images and what is seen may vary according to brand of scanner, settings, mode of gadolinium administration, and the possibility that gadolinium entry may favor the vestibule. Transtympanic tone burst electrocochleography is to date the simplest, cheapest and most sensitive technique for detecting cochlear endolymphatic hydrops to confirm a diagnosis of Meniere's disease.

Dynamics of pure tone audiometry and DPOAE changes induced by glycerol in Meniere's disease

The purpose of this study is to follow up the dynamics of pure tone threshold and DPOAE amplitude changes induced by glycerol with reference to its activity in the inner ear. Selection was made among 38 patients with Meniere’s disease for those having positive glycerol test. Pure-tone audiometry and DP-gram were performed in four series: as an initial examination before glycerol intake, 1, 2 and 3 h after. Audiometric changes formed distinct biphasal pattern at all frequencies between 250 and 4,000 Hz. The most dynamic pure tone threshold decrease occurred during the first hour. Between the first and second hour after glycerol ingestion there was a phase of no significant hearing changes. Further pure tone threshold decrease went on within the third hour reaching its top. Observing DPOAE changes, the highest DP amplitude growth occurred after the second and the third hour at DP-gram frequencies 2, 3 and 4 kHz. The fastest DP-amplitude increase was registered as well during the first hour after glycerol ingestion. In 11 persons with both audiometry and DPOAE positive glycerol test, parallel dynamics in the course of the glycerol test was observed. Biphasal glycerol test dynamics suggests the possibility of two mechanisms of glycerol activity in the inner ear.

Assessment of diagnostic parameters in meniere's disease

Meniere's disease has been ever served as one of the most debatable issue amongst the otologist. Various proposals for it's accurate diagnosis have arised in medical forefronts. The randomized study over here, of various diagnostic criteria in 52 nos are critically analysed in view of confirmation of clinically suspected Meniere's disease.Conclusions are drawn on basis of the autcomes of BERA,EcochG and caloric tests in form of individual as well cobined sensitivity in favour to attempt to standardize the deciding parameters in relation to the stage of the disease.

Audiovestibular testing in patients with Meniere's disease

In this article, the present state of the art with respect to audiovestibular testing for Meniere's disease (MD) is reviewed. There is no gold standard for MD diagnosis, and the classic dictum is that even the "best" tests yield positive results in only two-thirds of patients with MD. Still, we advocate the use and further investigation of advanced audiovestibular testing in patients with MD in an attempt to answer the questions that confront any clinician who cares for patients with audiovestibular symptoms.

Prognosis of sudden low-tone loss other than acute low-tone sensorineural hearing loss

CONCLUSION

In clinical practice, sudden low-tone loss other than acute low-tone sensorineural hearing loss (ALHL) shows a potential for recurrence.

OBJECTIVE

ALHL is often associated with recurrence and/or progression to Ménière's disease. We examined the prognosis of patients with sudden low-tone loss who were not classified in the audiometric definition of ALHL.

METHODS

Sixty-three patients diagnosed at the university hospital with idiopathic sudden low-tone loss of sensorineural hearing loss and without subjective vertigo were followed up in the long term with a mean of over 4 years. The rates of recurrence and/or progression to Ménière's disease for patients with low-tone loss type other than ALHL (non-ALHL) were compared with those for ALHL patients.

RESULTS

The recovery rate at the initial treatment was 47.6% for non-ALHL and 62.9% for ALHL. A Kaplan-Meier plot indicated that cumulative recurrence rates for non-ALHL were 20.2% at 1 year and 43.5% at 5 years, whereas the rates for ALHL were 12.2% at 1 year and 31.3% at 5 years. There was no statistically significant difference between the two patient groups.

Prognosis of low-tone sudden deafness - does it inevitably progress to Meniere's disease?

CONCLUSION

We conclude that not all low-tone sudden deafness (SD) patients suffered from endolymphatic hydrops even if they had vertigo attack at the onset and that electrocochleography (ECochG) was a useful prognostic tool.

OBJECTIVES

To investigate whether low-tone SD was a precursor of Meniere's disease and whether patients with low-tone SD suffered from endolymphatic hydrops.

PATIENTS AND METHODS

This was a retrospective case review in the university hospital. A total of 184 patients with low-tone SD were divided into two groups with single and recurrent episodes. The progress, follow-up audiograms, and ECochG results of the patients were reviewed and compared with those of patients with high-tone SD and Meniere's disease.

RESULTS

In all, 83 of 177 patients with low-tone SD unaccompanied by vertigo had recurrent hearing loss; 15 of the 83 developed vertiginous attacks. The remaining 94 patients had a single episode. Three of the seven patients with low-tone SD accompanied by vertigo had recurrent hearing loss; two of the three were subsequently confirmed to have Meniere's disease. The other four had a single episode. No difference in rate of progress from SD to Meniere's disease was observed among the low-tone and the high-tone SD groups. The average -SP/AP of each group with a single episode is smaller than that of other groups with recurrent episodes and Meniere's disease.

Incidence of virus infection as a cause of Meniere?s disease or endolymphatic hydrops assessed by electrocochleography

Meniere's disease (MD) may follow viral infection such as by neurotropic viruses known to invade the endolymphatic sac (ES) and provoke endolymphatic hydrops (EH). The objective of this study was to investigate whether neurotropic viruses may cause infection of the inner ear and provoke EH. Antiviral immunoglobulin (IgG) assay against herpes simplex 1 (HSV1), herpes simplex 2 (HSV2), adenovirus (ADV), varicella zoster virus (VZV) and cytomegalovirus (CMV) were performed in 109 patients with an advanced stage of MD and compared with those obtained from 26 patients operated on because of vestibular schwannoma (VS), who served as a control group, to evaluate whether there is an association between the IgG levels and the ECoGs summating potential/action potential ratio (SP/AP ratio) in the MD group. In MD patients, the IgG titre against VZV and ADV were significantly higher than in the control (schwannoma) group. However, no correlation was found between the IgG levels against ADV and VZV with the SP/AP ratio. Neurotropic viruses such VZV and ADV may play a role in the pathogenesis of MD, despite the absence of association between the levels of IgG titres and the SP/AP ratio.

Clinical Usefulness of Extratympanic Electrocochleography in the Diagnosis of Ménière’s Disease

OBJECTIVE

Electrocochleography has been introduced to aid the diagnosis of endolymphatic hydrops. The aim of this study was to evaluate the clinical effectiveness of extratympanic electrocochleography in the diagnosis of Ménière's disease.

STUDY DESIGN

The medical records of patients diagnosed as having Ménière's disease at the department of otolaryngology were reviewed retrospectively. Thirty-seven healthy ears were included to calculate the upper level of the 95th percentile range of the extratympanic electrocochleography variables.

SETTING

Tertiary referral university hospital.

PATIENTS

One hundred fifty-eight patients (97 women and 61 men) diagnosed as having Ménière's disease without previous treatments were included. A retrospective analysis of their medical records, electrocochleographic results, audiograms, and follow-up records was performed. The mean age was 48.6 years.

MAIN OUTCOME MEASURES

The upper level of the 95th percentile range of the extratympanic electrocochleography variables of normal subjects were calculated. Electrocochleography recording results were compared with the diagnostic scale and stage, presence of fluctuating hearing loss, and duration of symptoms.

RESULTS

The 95% upper limit for baseline summating potential and action potential ratio was 0.34. Sensitivity and specificity of electrocochleography in the diagnosis of Ménière's disease were 71% and 96%, respectively. The results statistically correlated with the Ménière's current diagnostic criteria and did not correlate with the stage of disease, presence of fluctuating hearing loss, or duration of symptoms.

CONCLUSION

Extratympanic electrocochleography may play an important role, especially in patients with less definite symptoms, but the diagnosis should also be anchored in the patient's clinical history, symptoms, and audiogram.

Diagnosis of Meniere's disease: routine and extended tests

Meniere's disease can compromise the quality of life of some patients in a manner so seriously that it can cause social segregation, even from family. Hearing loss, tinnitus, aural pressure, and disturbances in equilibrium added to an emotional instability frequently present in these patients may take them to a progressive state of solitude and depression, marking their lives by personal tragedy and making life a living hell. The clinical picture of Meniere's disease fluctuates, however. Individually, subsidiary examinations become impotent in diagnosing Meniere's disease. To be called Meniere's disease, the cause must be unknown; otherwise it would constitute Meniere's syndrome. Taking all of this into consideration, one would call this an unusual situation, or at least confusing. The lack of an etiologic diagnosis in medicine always creates anxiety for doctors and patients. What is considered to be either a routine or an extended test may change from service to service. The physician does not need to order all tests. What the physician needs is a protocol he or she trusts. Test results can vary, even depending on the moment when they are performed. More important than the number of tests ordered is the strategy by which the tests should be put together at that certain moment. The authors believe that one should have his or her own protocol for diagnosis, always beginning with a detailed history taking being guided by them most of the time. It is the authors' understanding that patients with Meniere's disease should be followed closely by their ear, nose, and throat doctor in episodes of vertigo or fluctuation of their hearing, tinnitus, or aural pressure. Should the patient be experiencing a stable period, a clinical visit along with an audiovestibular workup should be performed at least once a year. By monitoring the course of the disease, clinicians would be able to detect early changes in symptoms and/or test results, giving them the possibility to intervene clinically as early as possible in acute episodes of vestibulocochlear disorganization, protecting the inner ear, and minimizing sequelae from spells of hydrops. The authors believe that only the association of clinical sense and as many subsidiary tests as are useful will lead to a desirable level of certainty in the diagnosis of Meniere's disease, and will allow clinicians to presume bilateral involvement, monitor the development of the disease, intervene in its natural course, and idealize appropriate treatment.

Clinical usefulness of glycerol vestibular-evoked myogenic potentials: preliminary report

The detection of intense sound-induced vestibular-evoked myogenic potentials (VEMPs) on the sternocleidomastoid muscle comprises the basis of the saccular function test. In order to evaluate the endolymphatic hydrops (EH) of the saccule of the inner ear, a glycerol VEMP (GVEMP) test was performed in 15 patients with unilateral typical Ménière's disease (UMD) and 7 with delayed endolymphatic hydrops (DEH). Using the GVEMP test, 8 of the 15 patients (53%) with UMD were evaluated as being abnormal. In addition, a greater number of patients (67%) were judged to be abnormal when the results of the GVEMP test were combined with those from a glycerol dehydration test, trans-tympanic electrocochleography (ECochG) or furosemide vestibulo-ocular reflex test (FVOR). Four of the 7 patients with DEH (57%) showed abnormal results in the GVEMP test. In particular, in patients with the ipsilateral type of DEH, only the GVEMP test was able to detect the affected side. These findings suggest that the GVEMP test is a new and useful test for EH, and that a test battery comprising the GVEMP test together with one of the other three tests is useful for diagnosing EH of the inner ear.

Ménière's disease and delayed endolymphatic hydrops in children

In order to study the characteristics of pediatric patients (< or = 15 years at onset) with endolymphatic hydrops disorders, we selected 5 patients with Ménière's disease (MD) and 3 patients with delayed endolymphatic hydrops (DEH) from 7418 patients who had visited the Neurotological Clinic of the Toyama Medical and Pharmaceutical University Hospital between 1979 and 1999. Clinical features were characterized as follows: (i) pediatric MD patients were rare, comprising approximately 1.5% of all the 337 MD patients in the sample; (ii) a fluctuating hearing loss, strong positive response in glycerol test, high SP/AP amplitude ratio in electrocochleography and moderate positive response in furosemide vestibulo-ocular reflex test were recorded; (iii) in 2 of the 5 pediatric MD patients, vertiginous attacks had persisted for a long period and they had undergone surgical procedures (sac operation and vestibular neurectomy); and (iv) the ipsilateral type of DEH was observed in 2/3 children, and contralateral DEH in 1/3.

Summating potential & summating potential/action potential ratio in the diagnosis of Meniere's disease

This study assesses electrocochleographic (ECOG) potentials in a clinically defined Meniere's group and compares the results with those from a normal control group. Electrocochleography was done in 42 cases of Meniere's disease and was compared with 20 normal cases. All parameters of electrocochleography were studied with special emphasis on the summating potential/action potential (SP/AP) ratio. A SP/AP amplitude ratio of 0.49 was found in the Meniere' group as compared to the SP/AP ratio of 0.03 in the control group. Latencies of SP and AP were also studied and compared between two groups.

Combined Vestibular Neurectomy and Endolymphatic sac Shunt via the Retrosigmoid Approach in the Treatment of Ménière's Disease

The nature of surgical treatment for Ménière's disease has evolved from destructive to conservative in the interest of preserving hearing. We have performed a combined procedure that involves a vestibular neurectomy to control vertigo, which is followed by an endolymphatic sac shunt to control hydrops in 26 patients. Both procedures are performed via the retrosigmoid approach during the same surgical step. We believe this combination procedure is a worthwhile option to consider in order to achieve good control of vertigo and endolymphatic hydrops and to preserve hearing in patients with Ménière's disease.

Clinical study of elderly patients with Meniere's and related diseases

In order to study the characteristics of elderly patients (70 or over at onset) with endolymphatic hydrops disorders, we selected six patients with Meniere's disease (MD), five patients with delayed endolymphatic hydrops (DEH), and two patients with syphilis of the labyrinth (SL) from 7112 patients who had visited the Neurotological Clinic of the Toyama Medical and Pharmaceutical University Hospital during 1979-1998. Clinical features were characterized as follows: (1) Since 1990, the proportion of elderly patients increased as lifespans lengthened. (2) A narrow fluctuation in hearing, low positive rate on glycerol test, high positive rate of dominant-SP in EcochG, and the moderate abnormal rate of the oculomotor system tests were found. (3) The prognosis was relatively good. From these neurotological observations, it could be concluded that elderly patients with endolymphatic hydrops disorders were characterized by the multipathological finding of the endolymphatic hydrops and the complications of CNS disorders.

Use of electrocochleography in the diagnosis of Meniere's disease

OBJECTIVE

The diagnosis of Meniere's disease has always been a source of confusion. There is no single test that is definitive for the diagnosis. Recent advances have enabled clinicians to noninvasively test the function of the inner ear and its associated neural pathways. The electrocochleogram (ECOG) has been advocated as a reliable test that is diagnostic for Meniere's disease. This study was undertaken to assess the value of ECOG in establishing the diagnosis of Meniere's disease.

STUDY DESIGN

Patients who were suspected of having Meniere's disease were prospectively entered into a study of the diagnostic value of ECOG. Each patient had a complete evaluation including a detailed history, physical examination, laboratory studies, and audiometric tests.

SETTING

University otolaryngology clinic.

PATIENTS

A group of 199 patients who presented to a neurotology clinic and were suspected to have symptoms consistent with Meniere's disease.

INTERVENTION

ECOG testing.

MAIN OUTCOME MEASURES

Audiometric thresholds, action potential magnitude (AP), summating potential amplitude (SP), AP latency, and clinical evaluations were assessed.

RESULTS

The ECOG was found to correlate with historical and audiometric criteria that are used to diagnose the disease. The percentage of abnormal ECOG did not correlate with stage of disease or duration of time that symptoms were present.

CONCLUSIONS

The ECOG has limited value in the diagnosis of Meniere's disease. It appears to correlate with the length of time patients experience symptoms and their audiometric findings. It was not correlated with the number of symptoms that the patient experienced at the time that the study was conducted.

Effective anaesthesia for transtympanic electrocochleography

The objective of this study was to quantify the anaesthetic effect of EMLA cream during transtympanic electrocochleography (TTECochG) and thereby to determine if the application of EMLA should be recommended in routine practice of electrocochleography (ECochG). ECochG provides useful information in patients with inner ear fluid disorders. A major concern regarding transtympanic positioning of the electrode in ECochG is patient discomfort. Previous work has suggested that EMLA cream may make this technique more tolerable to patients. A prospective randomized study was performed evaluating the discomfort associated with unilateral TTECochG in a group where EMLA cream was used to anaesthesize the tympanic membrane (n = 24), and in a group where no anaesthesia was used (n = 22). A statistically significant difference was evident between the discomfort ratings of the groups (P < 0.0001, Mann-Whitney U test), the discomfort being greater in the no anaesthesia group. EMLA cream has thus been shown to alleviate the level of discomfort associated with TTECochG and so to be an acceptable modification of this technique.

Interinterpreter variability in determining the SP/AP ratio in clinical electrocochleography

Calculating the SP/AP ratio in electrocochleography requires the interpreting audiologist to unequivocally identify the peak of the SP wave form. If different points are selected, different SP/AP ratios will result. To investigate this effect, 50 electrocochleographic tracings were sent to 10 different audiologists (500 tracings). Twenty of the wave forms sent to each audiologist were identified as "easy," 10 as "somewhat difficult," 10 as "very difficult," and 10 as "no response." The ranges and standard deviations of the resulting SP/AP ratios were quite high. Analysis of variance showed statistically significant differences in the very difficult and no response group. There is significant interinterpreter difference among SP/AP ratios calculated from the same tracing. This variability affects clinical patient management and investigational projects.

A review of electrocochleography: instrumentation settings and meta-analysis of criteria for diagnosis of endolymphatic hydrops

This paper reviews the literature on instrumentation settings used for transtympanic (TT-ECOG) an extratympanic electrocochleography (ET-ECOG). There is wide variation regard to the applied stimulus, the settings and interpretation of ECOG results. For most physicians, the presence of endolymphatic hydrops is indicated either by the summating/action potential (SP/AP) ratio for click stimuli or the SP amplitude after tone bursts. Different upper limits have been proposed to discriminate hydropic from non-hydropic ears. Based upon a meta-analysis and classification criteria obtained from multivariate statistics, the authors propose that an SP/AP ratio with click stimulation > 0.35 using TT-ECOG, or > 0.42 using ET-ECOG, is indicative of hydrops. With tone burst stimulation set at a repetition rate of 30-40 stimuli per second, a SP of < -2 microV using TT-ECOG for at least one frequency within the range 0.5-8.0 kHz is considered pathologic.

Electrocochleographic findings: Menière's disease versus sudden sensorineural hearing loss

Electrocochleography was conducted in 185 patients with Menière's disease and 117 with sudden deafness. Electrophysiological findings from the two groups were compared in order to identify pathogenic similarities between the two conditions. Parameters investigated were the summating potential (SP)/action potential (AP) ratio, audiometric profiles and audiometric changes after medical therapy. A high SP/AP ratio was found in the patients with sudden deafness, thus supporting a possible hydropic aetiology in this group. In conclusion, electrocochleography can be considered a useful technique as it permits identification of an hydropic condition in certain cases of sudden deafness.

A preliminary report on the correlation of vestibular Meniére's disease with electrocochleography and glycerol test

Objective evaluation of vestibular Meniére's disease has been difficult due to the lack of audiometric findings. Thus inevitably, the existence of vestibular Meniére's disease is constantly being challenged. In recent years, electrocochleography (ECochG) has proved to be a useful tool to verify the presence of endolymphatic hydrops electrophysiologically. To further clarify the nature of this disease, we collected 40 patients prospectively who met the following conditions as diagnostic criteria for clinical vestibular Meniére's disease: i) episodic vertigo, ii) aural fullness, and iii) normal hearing. We implemented the glycerol test and extratympanic ECochG in addition to routine survey in these cases. The diagnosis was confirmed if either test result was positive. A retrospective collection of 24 cases who underwent endolymphatic sac surgery was made to evaluate in retrospect the existence of endolymphatic hydrops indirectly proved by successful surgery. Results showed a positive SP/AP ratio in 25 cases (62.5%) of which 7 had bilateral positive responses. The glycerol test was positive in 5 cases including 3 who also had positive ECochG responses. In the retrospective group, 4 cases exhibited an abnormally large SP/AP amplitude ratio at preoperative baseline conditions after general anesthesia. Twenty cases showed an SP/AP ratio within normal limits. Only 7 cases (29%) showed a decrease in the SP/AP ratio at different surgical steps. Short-term surgical results showed a 96% success rate of relief of vertiginous symptoms. Symptoms of fullness were completely controlled in 22 patients (92%). Hearing was preserved in 18 patients (75%). We conclude that i) the above-listed clinical criteria combined with these objective tests may prove to be very useful in the diagnosis of vestibular Meniére's disease, and ii) a successful control of vertigo and aural fullness after endolymphatic sac surgery indirectly indicates that endolymphatic hydrops is involved in vestibular Meniére's disease, sharing as it does, a pathophysiology that is similar to that of classic Meniére's disease.

Electrocochleography in endolymphatic hydrops using tone-pip and click stimuli

The use of electrocochleography (ECochG) in the identification of endolymphatic hydrops in Menière's disease, using either trans-tympanic or extra-tympanic recording techniques, has become very popular. The presence of an enhanced summating potential (SP) component is considered to be a diagnostic indicator of hydrops. The response evoked by a click stimulus is widely used in this investigation. The aim of this study was to assess the value of tone-pip stimuli for measurement of the SP component in patients with suspected Menière's disease. Extra-tympanic ECochG was recorded from a surface electrode positioned on the postero-inferior quadrant of the ear canal close to the tympanic annulus. Forty patients referred to the Evoked Potentials Clinic at the Queen's Medical Centre were studied. The combined summating potential and action potential waveform (SP/AP) were recorded using click and tone-pip stimuli. The pips had tone frequencies of 1 and 4 kHz and all stimuli were presented with alternating phase at a repetition rate of 10 per second. The percentage SP (%SP), width and latency characteristics of the SP/AP waveform were calculated for each stimulus condition. There were four patients (10%) with an enhanced tone-pip %SP when the click %SP was within normal limits. Width measurement of the tone-pip waveform at the onset point of the response was abnormal in 13 patients (33%) when a similar measurement of the click-evoked response was normal. There were nine of these patients identified by an abnormal width measurement at the 50% amplitude point of the SP/AP waveform. Both tone-pip frequencies were required in order to identify all these abnormal measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocochleography in the diagnosis of delayed endolymphatic hydrops

It is known that delayed endolymphatic hydrops (DEH) occurs in patients with unilateral and/or bilateral profound hearing loss. In the ipsilateral and bilateral types of DEH, no audiological tests can be performed on the affected ear because of profound deafness, although these tests can be done in the contralateral type. Electrocochleography (ECochG) was recorded on better hearing ears in both types of DEH. The results showed an increased negative summating potential (SP) in 6 out of 10 contralateral DEH patients whereas it could be measured in only one of 10 ipsilateral DEH patients. The mean SP/AP ratio of the contralateral type was 0.42 which was significantly larger than that of the ipsilateral type. The results suggest that contralateral-type DEH has the same pathology in the cochlea as Meniere's disease, and that ECochG can distinguish between these two types of DEH.

Changes in auditory evoked responses during intravenous lidocaine

Auditory evoked responses in 21 cases with tinnitus were recorded before and after the administration of intravenous lidocaine. A dosage of 1 mg/kg body weight was diluted with 20% glucose (20 ml) and administered intravenously over a one-min period. The loudness of tinnitus was evaluated during electrocochleography (ECochG) or auditory brain-stem response (ABR) recordings using a score between 0 and 11. The stimulus sound was a tone burst in a frequency that corresponded to the pitch of tinnitus. AP latency on ECochG and the inter peak latency (IPL) of wave I-III and wave III-V on ABR were prolonged momentarily and tinnitus was reduced. These findings reveal that the sites of action for lidocaine are both the inner ear and the brain-stem.

Electrocochleography in syphilitic hearing loss

Syphilitic labyrinthitis presents such symptoms as hearing loss, tinnitus, vertigo and/or dizziness, and is well known as one of the endolymphatic hydropic diseases. In order to elucidate the relationship between syphilitic hydrops and ECochG findings, we performed ECochG in patients with syphilis following our previously reported study of patients with Meniere's disease. Twenty-two patients who have been serologically and clinically diagnosed as having syphilitic labyrinthitis were examined with ECochG between December, 1982 and November, 1991. Of the 27 ears tested with ECochG, 2 showed no response due to severe hearing loss, and increased SP (SP/AP ratio > 0.37) was observed in 14 (56.0%) out of the remaining 25 ears. The SP/AP ratio of patients with syphilitic labyrinthitis was not significantly different from that of the patients with Meniere's disease or delayed endolymphatic hydrops, while it was significantly higher than that of the patients with sudden deafness and other types of sensorineural hearing loss. We conclude that the electrocochleographic features of endolymphatic syphilitic lesions resemble those in Meniere's disease.

Intraoperative electrocochleography of endolymphatic hydrops surgery using clicks and tone bursts

Seventy-seven ears of patients with Menière's disease (n = 69) and other ears with secondary endolymphatic hydrops (n = 8) underwent valved shunt surgery, and were monitored with intraoperative electrocochleography (ECoG) using clicks stimuli (n = 77), and both clicks and tone bursts (n = 37). Of the 41 ears in which the "baseline" measurement was > 35% summating potential to action potential (SP/AP) amplitude click ratio, 23 ears (56%) showed a significant ratio decrease (improvement). Twenty-six ears out of the 37 that were monitored by both clicks and tone bursts had abnormal absolute SP tone bursts amplitudes at "baseline" and 8 ears (31%) changed to normal at "closing". When tone burst ECoG information is combined with click stimuli, our basic understanding of click ECoG is enhanced and our ability to assess electrophysiologic changes intraoperatively is improved.

The role of summating potential in the diagnosis and management of Menière's disease

To assess the role of a negative summating potential (-SP) in the clinical diagnosis and management of Menière's disease, the relationship of -SP abnormality to clinical symptoms, hearing level and caloric test results was examined in 70 patients with unilateral Meniere's 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 Menière's disease basically in the cochlear partition at high frequencies.

The intravenously administered glycerol test

Three different methods of performing the glycerol dehydration test were evaluated. Method one involved the oral administration of 50 g of 50% glycerol solution; method two was the intravenous administration of 500 ml of 10% glycerol in saline with 5% fructose; and method three involved the administration of 200 ml of the same solution. It was found that intravenous administration was safe and did not give any unpleasant side effects. Both intravenously administered methods appeared to give similar rates of positive diagnosis for Menière's disease.