SP/AP area ratio in the diagnosis of Ménière's disease.

Conventional analysis of the click-evoked electrocochleogram includes measurement of the amplitudes of the cochlear summating potential (SP) and auditory nerve action potential (AP) to derive the SP/AP amplitude ratio. It is now well documented that an amplitude ratio where SP is elevated relative to AP may be a positive finding for endolymphatic hydrops in patients suspected of having Ménière's disease (MD). However, the incidence of an elevated SP/AP amplitude ratio in the general MD population is only approximately 60%. This relatively low value necessitates efforts to improve the diagnostic sensitivity of electrocochleography (ECochG) for MD. A review of early and more recent literature in this area indicates that consideration of both the amplitude and duration of ECochG components may help to achieve this goal. The present study combined these features to measure the "area" of the SP-AP complex in normal and MD populations. A software routine was used to measure the amplitude x duration area of the SP-AP complex in (a) normally hearing adults with normal SP/AP amplitude ratios (Group 1), (b) confirmed MD patients with elevated SP/AP amplitude ratios (Group 2), and (c) probable MD patients with normal SP/AP amplitude ratios (Group 3). Ninety percent of the confirmed MD patients in Group 2 displayed elevated SP/AP area ratios relative to the normative value established from Group 1. In addition, almost half of the probable MD patients from Group 3 displayed elevated area ratios. These findings indicate that measurement of the SP/AP area ratio holds promise for improving the sensitivity of ECochG in the diagnosis of MD.

Cochlear potentials in clinical audiology.

The recording of cochlear and auditory nerve potentials in humans via Electrocochleography (ECochG) has emerged as a valuable tool for a variety of clinical applications. This review consolidates current research on the use of cochlear potentials and ECochG in the clinical setting and identifies several areas in need of additional study. Methodological topics discussed include a review of ECochG recording approaches (i.e. transtympanic versus extratympanic) and issues related to choice of stimuli (clicks versus tonebursts). The review of current applications for cochlear potentials focuses primarily on the use of ECochG in the identification and treatment of Ménière's disease/endolymphatic hydrops (MD/ELH). Other uses for ECochG also are presented (e.g. intraoperative monitoring, enhancement of ABR wave I, estimation of hearing sensitivity). Several suggestions are offered to maximize the predictive value of ECochG in the diagnosis of MD/ELH.

Electrocochleographic effects of ear canal pressure change in subjects with Menière's disease.

This study examined the relationship between objective changes in electrocochleographic (ECochG) parameters and subjective changes in symptoms in a group of patients with Menière's disease/endolymphatic hydrops (MD/ELH) after application of positive and negative atmospheric pressure changes to the sealed ear canal. Our goals were to further examine the therapeutic effects of atmospheric pressure change on the treatment of MD/ELH, as reported by a series of Swedish studies, and to examine the utility of ECochG for monitoring these effects. By combining a clinical immittance unit and an evoked potential unit, ECochG responses were obtained from the tympanic membrane while different atmospheric pressures were applied indirectly to the middle ear via the external ear canal. For comparison, ECochG responses at various atmospheric pressures also were obtained for otologically normal subjects. For the MD/ELH group, there was a significant (p < 0.01) reduction in the abnormal summating potential/action potential (SP/AP) amplitude ratio, although the amplitude ratios did not become "normal." There was no significant effect of ear canal pressure change on ECochG components for the normative subjects. Although these findings were encouraging regarding the therapeutic effects of overpressure, they were not accompanied with changes in MD/ELH symptoms.

Progressive neural hearing impairment: case report.

This report describes a patient whose ability to understand speech had so deteriorated over 20 years time that she was being considered for a cochlear implant, despite the fact that pure-tone sensitivity loss had not deteriorated proportionately. An unusual combination of otoacoustic emissions (OAEs) and auditory evoked potential (AEP) results are described. Click-evoked and distortion product emissions were present and normal-appearing. Auditory brainstem and middle latency responses were totally absent but the N1-P2 complex of the long-latency response was present. The case illustrates the contribution of otoacoustic emissions to site of lesion testing. It also illustrates that the manifestations of pathology can appear in certain epochs of the family of AEPs without affecting the others.

Normal summating potential to tone bursts recorded from the tympanic membrane in humans.

The use of tone-burst stimuli for electrocochleography (ECochG) may offer certain advantages over conventional broad-band clicks. Namely, the summating potential (SP) component can be examined at different frequencies and may be easier to define and measure. To apply these findings clinically, it would first be necessary to establish SP amplitudes as a function of tone-burst frequency in normal listeners. The purpose of the present study was to do this using the tympanic membrane (TM) as the primary ECochG recording site. ECochG was recorded from 20 normal ears. Stimuli included 500-, 1000-, 2000-, 4000-, and 8000-Hz tone bursts presented randomly at 90 dB nHL. Mean SP amplitudes at these frequencies were +0.19, +0.17, +0.08, +0.10, and +0.22 microvolts, respectively. Although mean amplitudes were slightly positive regarding baseline, individual amplitudes varied between -0.41 and +0.73 microvolts. This study offers additional evidence that the SP to tone bursts can be recorded from the TM. The normative data provided should be useful for extended studies involving clinical populations.

Human summating potential to tone bursts: observations on tympanic membrane versus promontory recordings in the same patients.

Electrocochleographic responses to tone bursts and clicks were recorded from the tympanic membranes (TMs) and promontories of six suspected Meniere's patients. Although the majority of ears had normal summating potentials (SPs), regardless of recording site and stimulus type, some displayed amplitude-enlarged SPs at both sites and to both types of stimuli. The following observations were made from these patients regarding the choice of recording approaches and stimuli for ECochG: (1) Although SP amplitudes at the promontory were approximately four times larger than corresponding TM values, response "patterns" leading to diagnostic interpretation were the same at both sites; (2) the majority of patients who displayed enlarged SP amplitudes to tone bursts also had enlarged SPs to clicks; and (3) with tone-burst stimuli, the amplitude of the SP alone was sufficient for diagnostic interpretation of the ECochG waveform.

Prolonged I-III interwave interval in cerebellar astrocytoma.

We are reporting the case of a 41-year-old female diagnosed with a cerebellar astrocytoma. The tumor was detected after the patient was referred for MRI scan because of an abnormal ABR. The ABR was unusual as the I-V interwave intervals (IWIs) were within normal limits bilaterally, but the I-III IWI was prolonged by .40 msec on the left ear in comparison to the right ear. This case report illustrates the importance of the I-III IWI in the detection of retrocochlear pathology and the nonsequential generation of the components of the ABR.

Delayed endolymphatic hydrops following acoustic tumor removal with intraoperative and postoperative auditory brainstem response improvements.

A 36-year-old female with delayed endolymphatic hydrops (ELH) after acoustic tumor removal of the same ear is reported. She presented at our clinic with pressure, fullness, and tinnitus involving her right ear. She had an abnormal auditory brainstem response (ABR), and a computed tomography showed a right acoustic tumor. She underwent a complete tumor removal from a suboccipital incision with significant intraoperative and postoperative ABR improvements. Preoperatively, there was no fluctuation in her hearing and her electrocochleography (ECoG) was normal. She did well postoperatively, but 18 months after the tumor surgery she complained of noticeable fluctuating hearing loss with increased tinnitus and aural fullness of her right operated ear and nausea but no vertigo. Neurotological examinations showed a positive right urea dehydration and positive right ECoG for enhanced summating potential to clicks. She was diagnosed as cochlear Meniere's disease with delayed ELH, failed medical management and then underwent a valved shunt surgery for ELH to stabilize her hearing. Eight years after her acoustic tumor surgery and 6 and a half years after her ELH surgery she has stabilized hearing with normal ABR and ECoG. Her clinical course is presented and a pathogenesis of ELH is discussed.

Analog model of human click-elicited SP and effects of high-pass filtering.

Recent advances in electrode design have helped to rekindle clinical interests in noninvasive electrocochleography--to enhance auditory brain stem response (ABR) recordings (namely, wave I) and to screen Meniere's disease. The salient feature of the response in suspected cases of endolymphatic hydrops is an unusually large summating potential (SP). Since the SP is a DC potential, conventional wisdom suggests the use of relatively low cutoff frequencies (i.e., long-time constants) for recording, but this may degrade the recording due to the presence of excessive low-frequency noise. However, the click-elicited SP also is a transient of relatively short duration, considering the characteristics of the click. This may permit more liberal high-pass filtering with acceptable wave-form distortion. This is a report of findings obtained using an analog model for SP generation and recordings from normal subjects using an electrode placed directly on the tympanic membrane. Responses were obtained using various low-frequency cutoffs. Cutoffs up to 30 Hz caused little distortion. Even in the face of considerable distortion at the highest cutoffs (100 and 300 Hz), the SP remained detectable and the SP:AP essentially unchanged. Therefore, higher filter settings may be used in recording the SP than commonly assumed, although the decreased amplitudes of the component potentials may not be tolerable under all clinical test conditions.

Pediatric ABR screening: pass-fail rates in awake versus asleep neonates.

The auditory brainstem response (ABR) is commonly used as a neonatal hearing screening tool. The degree to which myogenic and/or movement artifact can confound the ABR in neonates, and the effect this has on screening pass-fail rates, although widely recognized, have not been reported. This study addressed these aspects in a clinical setting. Fifty-two high-risk neonates were screened in various states of activity (asleep, awake-calm, awake-active). Pass-fail rates between asleep and awake babies were significantly different (p less than 0.5), with the awake group displaying a much higher failure rate. There was no significant difference between the awake-calm and awake-active groups. Results indicate that activity state should be noted and considered along with the other factors that are generally blamed for false-positive results in neonatal ABR screenings.

A comparison of commercial auditory evoked potential units: the midpriced and luxury units.

This report represents the second of two providing a consumer-oriented comparison of commercially available auditory evoked potential units. The units compared here were those whose basic price was between $10,000-$30,000 ("midpriced"), and greater than $30,000 ("luxury"). The midpriced group included the Amplaid MK15, Bio-Logic Navigator and Traveler LT, Cadwell 5200A and Quantum 84, GSI-50, Nicolet CA-2000 and Compact Auditory, Nihon-Kohden Neuropak IV Mini, Madsen ERA2250, Siegen (Dantec) Neuroscope, and Tracor Nomad. The luxury units comprised the Bio-Logic Brain Atlas, Cadwell Spectrum 32 and Nicolet Pathfinder. Descriptive information and the names and addresses of users were solicited from the manufacturers for each of the above units. Questionnaires were sent to the users asking them for information on how their unit was used and to rate some of its features. The midpriced and luxury units offer more flexibility and options than less expensive (i.e., "economy") units. However, the basis for a given unit's price versus another's was not always apparent by a comparison of features or options. In general, users of the midpriced and luxury units rated the majority of their instruments' features highly. The lowest ratings were received for some aspect of the printer or print-out, and portability.

Tympanic ECochG and conventional ABR: a combined approach for the identification of wave I and the I-V interwave interval.

Identification of wave I and measurement of the I-V interwave interval (IWI) are important parameters of the auditory brain stem response (ABR). However, at low stimulus sensation levels, wave I may be absent in the presence of wave V when the ABR is recorded conventionally with scalp electrodes. Several studies have shown that the amplitude and detectability of wave I (or N1) can be enhanced via extratympanic electrocochleography (ECochG), and even more so with tympanic ECochG. In the present study, tympanic ECochG was combined with conventional ABR to compare the amplitude and sensitivity of N1, wave I, and wave V in normally hearing subjects, and to identify the N1-V IWI in hearing impaired subjects whose conventional ABRs did not contain a reliable wave I. For the normally hearing subjects, the amplitude of the N1 was considerably larger than the amplitudes of waves I and V of the conventional ABR and there was no significant difference between N1 and wave V thresholds. For the hearing impaired group, the combined ECochG-ABR approach allowed for the identification of N1 and measurement of the N1-V IWI in all subjects. Our results support the use of tympanic ECochG in combination with conventional ABR for certain audiological and neurological applications.

Electrocochleographic effects of ear canal pressure change.

A series of Swedish studies has shown that the application of middle ear over-pressure may be effective in ameliorating the symptoms associated with Meniere's disease. Other studies have shown that electrocochleography (ECochG) is an effective tool in the identification of Meniere's disease, especially in the presence of active symptoms. Based on the therapeutic potential of middle ear overpressure as a treatment for Meniere's symptoms and on the relationship between these symptoms and ECochG, we investigated the effects of ear canal pressure change on human electrocochleographic components in normally hearing subjects. An experimental system combining an immittance audiometer probe and ear canal electrode was utilized to record extratympanic ECochG when different atmospheric pressures were applied indirectly to the middle ear via the sealed ear canal. All ECochG parameters except for the duration of the whole nerve action potential (AP) of the auditory nerve were significantly affected by pressure changes in the ear canal. Effects included an enlargement of the summating potential (SP) amplitude and of the SP:AP amplitude ratio at pressures above and below 0 decaPa (daPa). An important implication of our findings is that the status of the middle ear must be taken into account in the interpretation of ECochG results.

A comparison of commercial auditory evoked potential units: the economy units.

As the first in a series, the present study was designed to compare and provide a consumer-oriented overview of commercially available auditory evoked potential (AEP) units with a basic price of less than $10,000 (i.e., the "economy" units). The following AEP units fell under this category: Algo-1/Algo-1PLUS, Amplaid MK-10, Nicolet Audit V, Bio-logic PASS, GSI-55, and Modular M-100. Descriptive information and the names and addresses of at least 10 users were solicited from the manufacturers for each of these units. Questionnaires were sent to the users, which asked them to provide information on how their unit was used and to rate some of its features. Results indicate that the economy units generally meet the needs and expectations of the users. They offer the advantages of being easy to use, portable, and reliable. Primary disadvantages relate to lack of flexibility, a problem that could generally be accommodated by upgrading to more sophisticated (and expensive) units.

Electrocochleography: methods and clinical applications.

The use of electrocochleography (ECoG) as a tool in the diagnosis, assessment, and monitoring of certain neuro-otologic disorders has attracted renewed attention in the United States. The use of ECoG among otologists and audiologists has increased in recent years, primarily due to the availability of relatively easily applied, noninvasive extratympanic electrodes. Information derived from ECoG recordings has been shown to be helpful in the objective identification and monitoring of Meniere's disease and endolymphatic hydrops. In addition, ECoG may be used to enhance our ability to observe the most peripheral component of the auditory brain stem response (Wave I) for routine clinical assessment or during intraoperative monitoring procedures in which certain structures of the ear are at risk for permanent damage. This article provides an overview of current techniques and clinical applications of ECoG.

Use of disposable ear canal electrodes in auditory brainstem response testing.

In this study a disposable ear canal electrode and stimulus delivery system (the Enhancer l) was evaluated for its clinical utility and the observed enhancement of the auditory brainstem response Wave I with its use. Data were collected from normally and abnormally hearing subjects, with both the conventional forehead-to-mastoid electrode array and the forehead-to-ear canal electrode arrangement provided by the Enhancer I ear canal electrode setup. For the normally hearing group, simultaneous acquisition of forehead-to-ipsilateral ear canal and forehead-to-ipsilateral mastoid electrode linkages was obtained. For the abnormally hearing subjects, a comparison was made between the Enhancer I system and the conventional forehead-to-mastoid electrode configuration used with a TDH-49 transducer for click delivery. Our findings indicate that Wave I was enhanced substantially when using the disposable ear canal electrode compared with the more conventional forehead-to-mastoid electrode configuration for both normally and abnormally hearing subjects. The Enhancer I electrode evaluated in this study proved to be painless for the subjects and extremely easy to use, requiring no more time in subject preparation than the more common surface recording electrode application.

Alternativa de acceso vascular para diálisis / Alternative for vascular access for dialysis

El paciente que en la actualidad ingresa a hemodiálisis tiene una prolongada perspectiva de vida. Sin embargo, dicha expectativa se reducirá notablemente si se tuiliza la vasculatura sin una estrategia racional. Una situación común es la de aquellos pacientes renales crónicos que evidencian "falta de arterias" apropiadas para canulación arteriovenosa. Esto se aprecia con cierta frecuencia en diabéticos, obesos. arterioscleróticos, enfermos con esclerodemia y en la miloidosis...Con el uso de catéteres profundos colocados quirúgicamente en yugular o en safena interna se logra: a)no requerimiento de venas de miembros superiores ni arterias, b)uso inmediato, c)simplicidad de colocación quirúrgica, d)utilidad aún con severa hipotensión, e)prolongada viabilidad, f) satisfactoria recirculación, g)satisfactorio caudal sanguíneo efectivo, h)apropiados clearences, i)ausencia de hemólisis, trombosis e infección.

Alternativa de acceso vascular para diálisis / Alternative for vascular access for dialysis

El paciente que en la actualidad ingresa a hemodiálisis tiene una prolongada perspectiva de vida. Sin embargo, dicha expectativa se reducirá notablemente si se tuiliza la vasculatura sin una estrategia racional. Una situación común es la de aquellos pacientes renales crónicos que evidencian "falta de arterias" apropiadas para canulación arteriovenosa. Esto se aprecia con cierta frecuencia en diabéticos, obesos. arterioscleróticos, enfermos con esclerodemia y en la miloidosis...Con el uso de catéteres profundos colocados quirúgicamente en yugular o en safena interna se logra: a)no requerimiento de venas de miembros superiores ni arterias, b)uso inmediato, c)simplicidad de colocación quirúrgica, d)utilidad aún con severa hipotensión, e)prolongada viabilidad, f) satisfactoria recirculación, g)satisfactorio caudal sanguíneo efectivo, h)apropiados clearences, i)ausencia de hemólisis, trombosis e infección. (AU)

Electrocochleography and symptoms of inner ear dysfunction.

We examined the relationship between electrocochleographic test results and symptoms associated with Meniere's disease-endolymphatic hydrops (MD-ELH). Extratympanic electrocochleography (ECochG) was performed on 55 consecutive patients (110 ears) suspected of having MD-ELH, and the results compared with the clinical symptoms of the patients on the day of recording. Referring symptoms included sensorineural hearing loss, aural fullness or pressure, tinnitus, vertigo, and all combinations of these four. There was a statistically significant difference between ECochG findings when symptoms were absent compared with when one or more symptoms were present. Furthermore, the presence of hearing loss combined with aural fullness or pressure was the strongest predictor of a positive ECochG, as characterized by an enlarged summating potential action potential amplitude ratio.