AP Latency Research Articles

Frequency-specific Electrocochleography and Traveling Wave Time as a Clinical Test for Menière's Disease.

Menière's disease is a clinical entity with no definitive objective testing. It has been hypothesized that underlying endolymphatic hydrops stiffens the basilar membrane leading to increased speed of the acoustic stimulus, therefore traveling wave velocity has been proposed as an objective test to aid in the diagnosis. The objective of this study is to compare electrocochleography frequency-specific action potential latency, basilar membrane traveling wave time, and summation to action potential (SP/AP) ratio in Menière's and non-Menière's patients. Tympanic electrocochleography was performed with frequency-specific action potential latency time and SP/AP ratio recorded. Patient demographics, symptoms, audiogram data, AAO-HNS classification of Menière's disease, management interventions, and follow-up were recorded. Statistical analysis was performed to compare outcome measures across patient groups, demographics, and clinical data. Ninety-one patients (182 ears) were included. There was a significant difference between a "definite" Menière's diagnosis and an "unlikely" or "probable" diagnosis by an average of 13 dB HL for the pure-tone thresholds at 250 Hz on the affected side (p = 0.006). There was no significant difference in pure-tone thresholds at any other frequency, AP latency at any frequency, or AP/SP ratio between the different Menière's classification groups. Our study fails to show significance of the traveling wave velocity as an objective test for Menière's disease. A significant correlation was found with low-frequency hearing loss between AAO-HNS Menière's classification groups.

An analysis of electrocochleography in patients with OSAHS

Objective:To investigate the values of electrocochleograph（ECochG）in patients with OSAHS. Method:ECochG was performed in 31 (62 ears) OSAHS patients (moderately 5 cases, severely 26 cases) and 28 healthy adults (56 ears). AP latency ，AP amplitude and SP/AP were measured and analyzed. Result:There was no difference between the two groups in SP/AP amplitude ratio（P>0.05） while both AP latency（P<0.05） and AP amplitude（P<0.05） were significantly different. Conclusion:ECochG can confirm the damage of cochlear and auditory nerve near the cochlear segment in patients with moderate to severe OSAHS.

Normative data for TM electrocochleography measures

ObjectiveEstablish normative data for tympanic electrocochleography (TM ECochG) parameters in normal hearing adults without Ménière's disease's (MD) symptoms. Describe TM ECochG variables that help to distinguish normal from MD ears. Material and methodsWe enrolled 100 subjects (N = 200 ears), 59 females, aged between 19 and 71 years from 09/2010 to 04/2014. Inclusion criteria: normal otomicroscopy, hearing thresholds ≤25 dB nHL from 250 to 4000 Hz, normal tympanogram, no symptoms of MD according to the AAO-HNS 1995 criteria and Gibson's score <7. We excluded subjects with dizziness, aural fullness or other symptoms of endolymphatic hydrops. The following parameters were analyzed: SP/AP amplitude ratio, SP/AP area ratio and the difference between AP latency with rarefaction and condensation stimuli. ResultsThere was no significant difference between right and left ears (Intraclass correlation coefficient < 0.6). SP/AP amplitude ratio varied between 0.084 and 0.356 and SP/AP area ratio between 0.837 and 1.671 (percentiles 5 and 95). The AP latency difference to rarefaction and condensation clicks was between 0.0 and 0.333 ms. ConclusionNormative data for TM ECochG parameters were established in 100 normal hearing subjects without MD. These data can be used to distinguish normal from pathological findings and in follow-up of MD patients.

Summating Potential‐Action Potential Waveform Amplitude and Width in the Diagnosis of Menière's Disease

It has been suggested that analyzing the width and amplitude of the summating potential-action potential (SP-AP) waveforms can increase the sensitivity of electrocochleography. The objective of this study was to evaluate the ratio of SP to AP amplitude (SP/AP) and SP-AP waveform width, as well as the AP latency difference to condensation and rarefaction clicks, for the diagnosis of Menière's disease. This was a prospective, controlled study. We used transtympanic electrocochleography to evaluate 21 patients with definite Menière's disease and 19 normal-hearing patients with other cochleovestibular disorders, comparing SP/AP, AP latency difference, and SP-AP waveform widths as well as calculating the diagnostic sensitivity of these parameters. Mean SP-AP waveform width was 1.89 ms in the study group and 1.58 ms in the control group. Mean SP/AP was 0.37 in the study group and 0.22 in the control group. The mean product of SP-AP waveform width and SP/AP was 75.26 ms% in the study group and 34.60 ms% in the control group. Mean AP latency difference was 0.13 ms in the study group and 0.07 ms in the control group. For the parameters evaluated, the differences between the groups were statistically significant. In the study group, the sensitivities for the width of the SP-AP waveform, the SP/AP, and the AP latency difference were 33.3%, 52.4%, and 23.8%, respectively. The use of the parameters evaluated did not increase the sensitivity of the electrocochleography, whether used in isolation or in conjunction with the SP/AP. Determining SP/AP presented the greatest sensitivity.

Use of electrocochleography in the diagnosis of Meniere's disease.

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. 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. University otolaryngology clinic. A group of 199 patients who presented to a neurotology clinic and were suspected to have symptoms consistent with Meniere's disease. ECOG testing. Audiometric thresholds, action potential magnitude (AP), summating potential amplitude (SP), AP latency, and clinical evaluations were assessed. 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. 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.

Electrocochleographic study of acute low-tone sensorineural deafness

We assessed 53 patients with acute low-tone sensorineural deafness (LTSD) over the past 10 years using the transtympanic-electrode technique of electrocochleography. The audiometric diagnostic criteria were as follows: Average hearing level at the lower two frequencies (250, 500Hz) greater than 30 dB, and of the higher three frequencies (2, 4, 8kHz) less than 20 dB. Patients were divided into three groups on the basis of their electrocochleographic findings; 33 cases of the endolymphatic hydrops type, 17 cases of the hair cell damage type and 3 cases of the neural damage type. The outcome of these patients was assessed together their electrocochleographic findings. The results obtained were as follows: 1) Most of the improved cases were of the endolymphatic hydrops type and in females in their twenties. All of the improved cases showed high AP and -SP amplitude, but not dominant -SP, and exhibited slight prolonged AP latency. Satisfactory CM responses at 500 Hz were also found. 2) Most of the hair cell damage type exhibited no change, and some unrecovered cases of the endolymphatic hydrops type progressed to Meniere's disease.

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.

か電図ＣＭの遅れとＡＰ（Ｎ１）潜時曲線との比較

か電図ＣＭの遅れとＡＰ（Ｎ１）潜時曲線との比較

Electrophysiological studies on the hydropic animals with special analysis as an animal model of Meniere's disease

The endolymphatic hydrops was made by the obliteration of the endolymphatic sac in 62 albino guinea pigs. AP, CM and SP were examined at the 1st, 2nd, 4th and 12th postoperative weeks and the results obtained were analysed in comparison with the audiological and electrocochleographical findings in Meniere's disease. Although abnormal SP was frequently found in the both groups, its appearance rates as a function of the time elapsed after the surgery or the first attack of Meniere's disease were different in these two groups. The AP and CM thresholds in the ani-mal were elevated with the similar time course as the progressive loss of hearing in Meniere's disease. The AP latency was prolonged in some of 12 weeks animals. This result was in accordance with that of Meniere's disease in which its prolongation was observed only in patients with long history.

Effect of hypothermia on the cochlear potentials.

The effects of hypothermia upon the cochlear potentials were studied in 30 guinea pigs. Particular attention was paid to the transient increase in AP amplitude at a moderate temperature. CM and AP were recorded via an Ag-AgCl lead placed on the round window membrane. Although the CM amplitude and threshold, and the AP latency and threshold were both impaired concomitant with the lowering of body temperature, the AP amplitude exhibited a transient increase at the beginning of cooling (peak at 30 degrees C) and a decrease thereafter. Narrow-band analysis of AP revealed that this phenomenon was most prominent in the high-frequency region. When the cochlear efferent fibers (crossed and uncrossed olivocochlear bundle) were cut, this transient increase in AP amplitude disappeared. This phenomenon seems to be due to the difference in sensitivity to hypothermia between the efferent and afferent fiber systems.

A comparison of AP and ABR tuning curves in the guinea pig

AP and ABR tuning curves were measured using a forward masking paradigm in guinea pigs with chronically implanted electrodes. Measurements were made before exposure to wide-band noise and at several intervals after exposure. The noise exposure was sufficient to produce temporary threshold shifts up to 60 dB lasting several days. Results showed similar reductions in Q 10, tip-to-tail ratio and slope of simultaneously recorded AP and ABR tuning curves as a function of threshold shift following noise exposure. Tuning curves based on changes in response latency are presented as well as tuning curves based on changes in response amplitude. AP and ABR latency tuning curves showed similar form and changes with hearing loss as amplitude tuning curves. The similarities between AP and ABR tuning characteristics provide evidence that the ABR is sensitive enough to peripheral changes to be useful as a tool to study auditory frequency selectivity. The similarities between amplitude and latency tuning characteristics suggest that information regarding frequency selectivity of the auditory system can be obtained using response latency as well as response amplitude.

A comparison of AP and ABR tuning characteristics in the guinea pig

AP and ABR tuning curves were measured using a forward‐masking paradigm in guinea pigs with chronically implanted electrodes. Measurements were made before exposure to wide‐band noise and at several intervals after exposure. The noise exposure was sufficient to produce temporary threshold shifts up to 60 dB lasting several days and resulted in a systematic widening of both AP and ABR tuning curves and a reduction in tip‐to‐tail ratios. No significant differences were found between simultaneously recorded AP and ABR tuning curves as measured by Q10, tip‐to‐tail ratio, or the slope of the tuning curves. Tuning curves obtained by measuring AP and ABR response latency as a function of masker level, showed similar form and changes with hearing loss to those based on amplitude of response. The similarities between AP and ABR tuning characteristics provide evidence that the ABR is sensitive enough to peripheral changes to be a useful tool in the study of auditory frequency selectivity.

Ultrasonic electrocochleography in guinea pig.

In order to obtain information about how ultrasonic stimuli are perceived (USP) in man, guinea pig cochleae were stimulated by bone conduction with frequencies (98.8 and 143.5 kHz) above the normal auditory field of this animal. The cochlear potentials recorded consisted of CM, SP and AP originating from the basal turn of the cochlea, and were found to be influenced by asphyxia, administration of ethacrynic acid, hypothermia and change of interstimulus interval. In addition, in kanamycin-treated animals the mean AP amplitude decreased to about one fourth of the normal value, and the mean AP latency increased significantly. These findings suggest that there is no special sense organ for the detection of USP but that such sounds activate hair cells in the basal turn of the cochlea.

超音波刺激によるか電図

In order to obtain information about how ultrasonic stimuli are perceived (USP) in man, guinea pig cochleae were stimulated by bone conduction with frequencies (98.8 and 143.5 kHz) above the normal auditory field of this animal. The cochlear potentials recorded consisted of CM, SP and AP originating from the basal turn of the cochlea, and were found to be influenced by asphyxia, administration of ethacrynic acid, hypothermia and change of interstimulus interval. In addition, in kanamycin-treated animals the mean AP amplitude decreased to about one fourth of the normal value, and the mean AP latency increased significantly. These findings suggest that there is no special sense organ for the detection of USP but that such sounds activate hair cells in the basal turn of the cochlea.

内リンパのう閉鎖および内リンパのう吸引による聴神経複合電位（ＡＰ），加重電位（ＳＰ），か牛マイクロホン電位（ＣＭ）の変化

The changes of AP, SP and CM were investigated in accordance with the grade of endolymphatic hydrops which was produced by endolymphatic sac obliteration in the guinea pigs. Also, AP, SP and CM were measured in animals in which the endolymphatic sac was suctioned. The results obtained were as follows:1. In animals with a minimum endolymphatic hydrops, a super-normal AP and CM responses were obtained in a few eases.2. With the increase of endolymphatic hydrops, CMs were reduced, where as APs at intensive stimulation were relatively well preserved.3. With the increase of endolymphatic hydrops, the potentials of positive SP were reduced, and a few cases showed the potential change to be a negative SP.4. With the increase of endolymphatic hydrops, the AP latency was increased.5. In endolymphatic sac suction, AP and CM responses at intensive stimulation were well preserved. A slight endolymphatic hydrops was observed. The potential of positive SP was reduced, and a few cases showed the change to cause a negative SP.6. In this series of experiments, the degeneration of the organ of Corti was hardly seen under the light microscope. It is suggested that polarity of positive SP observed in control was influenced to deflect towards negative SP by the increase of endolymphatic hydrops and the change of the biochemical component of the inner ear fluids.

Reaction time adaptation at lower frequencies and possible implications

Davis and Weiler (1975) found that significant decreases in reaction time could be measured as a function of exposure to an adapting tone. Following Davis' procedure in the present study, change in reaction time for 22 normal hearing individuals was measured with a 50-dB SPL, 400-Hz test tone and a 50-dB SPL, 500-Hz adapting tone presented for seven minutes. In counterbalanced fashion, a 500-Hz test tone with a 400-Hz adapting tone was tested to determine the possibility of contrasting effects as a function of tonotopic position of the two frequencies. A significant increase in reaction time was found using the 400-Hz test tone (p &amp;lt; 0.01) while no significant time increase was found using the 500-Hz test condition. The significantly increased reaction time could be partially attributed to the effects of passage of the traveling wave through the 500-Hz adapted region whereas the 500-Hz test tone does not completely overlap with the 400-Hz adapting tone. The significant increase in reaction time contrasts with Eggermont's (1979) decrease in AP latency in recruiting ears.