Rolf-D. Battmer

Benefits of bilateral electrical stimulation with the nucleus cochlear implant in adults: 6-month postoperative results.

Objective: To evaluate the benefits of bilateral electrical stimulation for hearing-impaired adult subjects using the Nucleus 24 cochlear implant in a multicenter study, and to compare and quantify performance on speech perception measures in quiet and in noise and localization ability for unilateral and bilateral cochlear implant use. Design: Repeated single subject measures were carried out for each subject, with each subject serving as their own control. Assessment of unilateral and bilateral listening conditions for performance on tests of speech comprehension and sound localization were performed. Speech comprehension measures were performed in quiet at 0 degree azimuth and in the presence of background noise simultaneously presented from the same speaker and spatially separated by 90 degrees, at S+45°N45° and at S−45°N+45°. Test materials included Freiburger monosyllabic words, Oldenburger sentences, and the Hochmair-Schulz-Moser sentences. Tests of localization were performed in the horizontal plane with 12 speaker locations 30 degrees apart using a shortened sentence stimulus from the Hochmair-Schulz-Moser sentences at two possible presentation levels of 55 and 70 dB sound pressure level for assessment of directionality. The binaural advantage provided by bilateral stimulation was calculated with respect to each ear separately, classified as either the better or poorer performing ear for each speech material in quiet and in noise test conditions. For localization of sound, the binaural advantage was compared with left and right ears separately. Paired comparisons for performance data in all conditions were carried out by considering measurements for each subject in different conditions as paired observations and applying the Student’s t test to determine the statistical difference between the data sets. Setting: Tertiary referral centers with a cochlear implant program. Patients: Thirty-seven profoundly hearing-impaired adults were enrolled in the study, 22 simultaneously and 15 sequentially bilaterally implanted. All patients received the Nucleus 24 cochlear implant and used the Nucleus SPrint or ESPrit 3G speech processor, with the vast majority using the ACE speech coding strategy. Results: For spatially separated speech in noise conditions, an interaural performance advantage for the ear closest to the speech source (i.e., with a superior signal to noise ratio) compared with that for the ear closest to the noise source (i.e., with an inferior signal to noise ratio) is consistently demonstrated regardless of whether it is the better or poorer performing ear closest to the speech signal. This is referred to as a significant binaural head-shadow benefit, resulting in a mean improvement between −10 dB and −11.4 dB in the critical signal to noise ratio required for 50% speech comprehension for the Olden-burger sentences and a mean improvement in the maximum score of 42% to 55% for the ear closest to the speech signal over the ear farthest away for the Hochmair-Schulz-Moser sentences. Bilateral stimulation is always observed to provide a performance advantage over the unilateral listening condition for either ear when ipsilateral to the noise source. In addition, as demonstrated by approximately half the subjects tested in noise with the Hochmair-Schulz-Moser sentences, a performance advantage of bilateral stimulation may be observed over the better ear alone when positioned ipsilateral to the speech signal, which is referred to as a binaural squelch effect. On average, for the group, this resulted in a statistically significant improvement in speech comprehension scores of 8% in the bilateral listening condition compared with the scores for the better ear alone. Through assessment of comprehension of coincidental speech in noise and speech in quiet, a significant benefit of binaural redundancy was noted for the group for Oldenburger sentence scores in noise and in quiet compared with unilateral scores for either ear and for the Freiburger monosyllabic words in quiet in comparison with the better ear alone scores. Binaural stimulation also led to a significant improvement in localization ability over either monaural condition, with the root mean square degrees of error reduced by 38 degrees compared with that observed for unilateral stimulation. Conclusion: Similar to what has been observed for bilateral acoustic stimulation in the past, bilateral electrical stimulation provides the foundation for the potential advantages of the head-shadow effect, providing a binaural head-shadow benefit and binaural auditory processing such as binaural redundancy and binaural squelch effects, all of which combine to lead to improved speech comprehension over unilateral listening conditions. The combination of improved speech comprehension and improved localization ability made available through bilateral electrical stimulation provides the necessary foundation to further assist the hearing-impaired listener to better cope with communication in the everyday listening situation both in noise and in quiet.

Electrically Elicited Stapedius Reflex in Cochlear Implant Patients

Electrically elicited stapedius reflexes were examined in 25 deaf patients who had received a 22-channel Clark/NUCLEUS cochlear implant. Using an apical, a medial and a basal electrode pair, different stimulation positions within the cochlea and different stimulation modes were examined. For threshold determination, 10 reflexes were averaged with reflexes recorded on the nonoperated side. Reflexes were elicited in 19 of the 25 patients (76%); a saturation of reflex amplitude could be recorded in 14 (56%) subjects. In two additional cases, a reflex could be obtained by increasing the bipolar stimulation width (changing the stimulation mode). In comparison with different stimulation positions within the cochlea, the stimulation of apical electrodes produced more distinctive reflexes and required lower current levels. An increase in the bipolar stimulation width also decreased the intensity required for stapedius reflex threshold. Our data suggest that stapedius reflex evaluation may be a useful tool for speech processor fitting.

A review of device failure in more than 23 years of clinical experience of a cochlear implant program with more than 3,400 implantees.

Background: During the last 25 years, the cochlear implant (CI), an active implantable assistive hearing device designed to provide electrical stimulation to the inner ear of the profoundly hearing-impaired individual, has been provided to more than 150,000 recipients worldwide. More recently, implants have been placed in young children as young as 6 months old. With the expectation of lifelong implant use, as with all active implantable medical devices, CI device failure is an inherent risk. Comprehensive, transparent, and comparable information on the incidence of device failure is essential to support individual CI candidate decisions and that of those responsible for the CI program. Methods: An examination and analysis of our internal electronic database for more than 23 years of CI implant procedures in 3,417 recipients were performed. The cause and incidence of device failure per model and implant type were reported as cumulative survival rates (CSRs). Results: Our experience shows that at 6 years postimplant, there are significant differences in percent CSR and failure modes between implant CI models and CI brands for children and adult CI users. Typically, the percent CSR has increased for successive generations of implant models but not without exception. Failure modes are most commonly related to impact, electronic dysfunction, or leakage. After device failure, explant-reimplant is a safe and acceptable treatment option. Conclusion: Percent CSR for CI devices at comparable postimplant time intervals varies, and as such, this information should continue to be carefully and systematically monitored and used by clinicians during counseling to support decisions by CI candidates, CI programs, and assist manufacturers in future developments.

An integrity test battery for the Nucleus Mini 22 Cochlear Implant System.

The probability of system failures increases as the number of cochlear implants increases throughout the world. Whether a malfunction is a technical or physiological problem remains to be defined, particularly in very young children, while a psychogenic hearing disorder after implantation must not be excluded in adults. The battery of objective measurements used clinically at the Medizinische Hochschule, Hannover has provided useful diagnostic information for distinguishing possible causes of failure. In a normally functioning device, an electrical signal equivalent to the biphasic rectangular stimulation pulse can be recorded by measuring skin potentials from surface electrodes placed on the mastoid of the implant side and the forehead. The signal from the stimulated implanted electrodes is derived by applying a constant pulse rate. Signal averaging is not necessary. If no signals are observed, a non-functioning device should be suspected. If the device works normally, function of the auditory pathways can be examined by recording the electrically elicited stapedius reflex or electrically evoked brain-stem responses. In our experience with more than 450 cochlear implant patients, eight internal device failures occurred, while an additional three patients had either reduced or no hearing sensations due to a disorder of the auditory pathways.

The brain stem response SN10, its frequency selectivity, and its value in classifying neural hearing lesions

ZusammenfassungDie Komponente P6 der Hirnstammreizantwort ist nur auf das Hören im Hochtonbereich ≥2 kHz zu beziehen, läßt sich aber bis an die Hörschwelle verfolgen. Die Hirnrindenreizantwort N90 dagegen ist frequenzspezifisch, bis an die subjektive Hörschwelle heran jedoch kaum zu erfassen. Die langsame Hirnstammkomponente SN10 (Davis und Hirsh 1979) soll unbeeinflußt durch medikamentösen Schlaf Auskunft auch über das Hörvermögen im Tief- und Mittelfrequenzbereich geben und wäre damit eine ideale Ergänzung zur schnellen Komponente P6.An einem Kollektiv von Normalhörenden und Innenohrkranken mit unterschiedlichen Frequenzgängen wurden die Hirnstammreizantworten P6 und SN10 simultan abgeleitet. Als Reiz verwendeten wir Tonpips frequenzunabhängiger An- und Abstiegsflanke von je 2 ms und einem Plateau von ebenfalls 2 ms. Die Schwelle der SN10-Reizantwort liegt im Mittel um ∼ 10 dB über der subjektiven Hörschwelle. Die Konstanz der Latenzen entspricht derjenigen von P6. Die Frequenzspezifität dieser relativ langsamen Hirnstammreizantwort ließ sich durch Vergleich der P6- und SN10-Reizantworten mit dem Verlauf der subjektiven Hörschwelle belegen.Die topodiagnostische Bedeutung der Komponente SN10 in Verbindung mit der Hirnstammreizantwort P6 und der Hirnrindenreizantwort N90 wird an einem Fall neuraler Hörstörung aufgezeigt.SummaryThe component P6 of the brain stem is only to be related to the hearing ability in the high tone range of ≥2 kHz, but it can be traced up to the hearing threshold. The cortex response N90, on the other hand, is frequency-specific, but it can hardly be recorded up to the subjective hearing threshold. The slow brain stem response SN10 (Davis and Hirsh 1979), unaffected by medicamented sleep, shall give information about hearing ability in the low and medium frequency range and may thus be an ideal complement to the fast response P6.In a number of normal hearing people and patients with sensorial hearing impairment of different frequency characteristics the brain stem responses P6 and SN10 were simultaneously recorded. As stimuli we used tone pips of a rise and fall time independent of frequency of about 2 ms and with a plateau of 2 ms as well. The mean threshold of the SN10 response is about 10 dB above the subjective hearing threshold. The constancy of the latencies corresponds to that of P6. The frequency selectivity of this relatively slow brain stem response is proved by comparing the P6 and SN10 responses with the course of the subjective hearing threshold.The topodiagnostic significance of the wave SN10 in connection with the brain stem response P6 and the cortical response N90 is shown in a case of neural hearing impairment.

Storage of audiometric data — Online — with a small computer

ZusammenfassungMit Hilfe eines Audiometers, das über einen zusätzlichen seriellen Ausgang verfügt, eines Rechners (DEC PDP 11/03) sowie eines Eingabe- und Sichtgerätes (DEC VT 55) lassen sich audiometrische Meßdaten on-line speichern, digital ordnen und diagraphisch wiedergeben. Die Eingabe kann man auf dem Display jederzeit kontrollieren und wie ein Audiogramm lesen. Für die Übertragung ist jeweils lediglich die Betätigung eines Knopfes am Audiometer notwendig. Ton- und Sprachaudiogramm erscheinen auf dem Display in getrennten Diagrammen; unter der Tonschwelle sind außerdem die Ergebnisse des SISI- und des Lüscher-Tests sowie die Stapediusreflexschwelle vermerkt, innerhalb des Tonschwellenaudiogramms die Meßpunkte des Fowler- und des Langenbeck-Tests. Für zusätzliche Befunde stehen drei Zeilen Bemerkungen zur Verfügung; sie werden über die Tastatur des Sichtgerätes eingegeben.Wahlweise kann eine rechnergesteuerte Vertäubungshilfe genutzt werden; unabhängig davon werden auch die Überhörwerte und die genutzten Geräuschlautstärken gespeichert.Die Papierdokumentation kann in Form einer Hardcopy oder gegebenenfalls als vierfarbiger Plotterausdruck erfolgen. Statistische Zusammenstellungen sind ohne weitere Aufbereitung möglich.SummaryFor online storage of audiometric measuring data we use an audiometer with serial operating output, a computer (DEC PDP 11/03), and a graphic terminal (DEC VT 55). The data can be controlled at any given time on the display and read like an audiogram. To transmit the data it is mainly only necessary to activate one button on the audiometer in addition.Pure tone and speech audiograms appear on the display in separate diagrams; in addition, beneath the pure tone threshold the results of the suprathreshold tests and the impedance measurement are indicated. For additional observations three lines are left available. If desired, a computer-supported masking aid can be used; independent of this, cross-heard values and applied masking noise intensities are stored.Paper documentations can achieve success as a hardcopy or as a four-coloured plotter print. Statistical groupings are possible without further processing.

Zum diagnostischen Wert der ipsilateral ausgelösten Impedanzänderung des Trommelfells

SummaryThe ipsilateral registration of impedance change is necessary in case of unilateral cochlear or retrocochlear disease with middle ear impairment of the other ear and, therefore, impossibility of contralateral evocation of the reflex. If contralateral evocation fails, moreover, it will be useful in order to clarify, whether the evocation did not succeed or the registration at the contralateral ear; thus enabling a differentiation between lesions of the reflexes afferent and efferent way.In ipsilateral impedance-change-measurements it should be distinguished between an increase of the acoustic impedance (— as searched for — turn to the right at the balancemeter), and a decrease of it (turn to the left at the balancemeter).The “turns of the left” at ipsilateral evocation occur without latency and only at SPL 100 db or more. They can be observed in patients suffering from otosclerosis, complete deafness and in dissected temporal bones as well. This acoustic-mechanical effect rises at high sound pressures from the non-linearity of the sound-field, which produces an extra pressure unbalancing the pressure before and behind the tympanic membrane. This effect may interfere with the real reflex-response, but only at more than 100 db SPL; however, it must be distinguished from the proper response in order not to find the reflex falsely positiv.In three clinical examples (two patients with multiple sclerosis, one patient with cerebello-pontine angle lesion), the absence of ipsilateral impedance reflexes (isolated or additional) is demonstrated.

Simultaneous recording of fast and slow auditory evoked potentials (Slow-Fast-Simultaneous-ERA, SFS-ERA)

SummaryIn order to reduce measurement time we have used part of the interstimulus interval of the slow cortical responses to record fast brain stem responses. For this purpose we reconstructed a programmable audiometer and preamplifier which are controlled by a computer. These, with 1/4 ms-click and tone-burst stimulation simultaneously gained fast and slow responses, not only give a frequency-related view of the threshold and the kind of hearing loss — because of amplitude and latency —, but also in some cases — because of differences between both responses — give ideas of the possible location of the hearing impairment through the auditory pathways. The audiological value of this new method is discussed and explained by giving examples of two interesting cases, one central-neural hearing loss and one questionable aggravation.

The automatic tone decay test as part of dynamic measurement of threshold

ZusammenfassungWeil nur die dynamische Registrierung der Tonschwelle Auskunft geben kann über pathologische Adaptation bzw. Hörermüdung und über die Aggravation, wurde auch der Schwellenschwundtest automatisiert. Dies gelang durch Umbau des Grason-Stadler-Békésy-Audiometers und inzwischen auch durch die Entwicklung eines speziellen Gerätes aus integrierten Schaltkreisen. Registriert wird mit einem handelsüblichen x-y-Schreiber, der zugleich für die Impedanzmessung verwendbar ist. Der Patient reguliert beim automatischen Schwellenschwundtest selbsttätig die Lautstärke immer nur so weit herauf, daß der Ton wieder gehört wird; zwischenzeitlich bleibt die Lautstärke konstant. So entstehen flache (Adaptations-) bzw. steile (Hörermüdungs-)Kurven, die mit der Békésy-Dauertonkurve korrelieren, deren Separation aber über die der Dauertonkurve eventuell hinausgeht. Der Schwellenschwundtest ist — im Gegensatz zu allen überschwelligen Tests — in seiner Aussage unabhängig vom Ausmaß des bestehenden Hörverlustes; er kann deshalb Auskunft geben über die Art der Hörstörung, wenn die Routine-Hörschwelle noch der Norm entspricht.SummaryOnly dynamic recording of the tone threshold can give information on pathologic adaptation, auditory fatigue, and aggravation. We have therefore automated the tone decay test. This was achieved by modifying the Grason-Stadler audiometer E 800 and, concurrently, by developing a special device with integrated circuits for this purpose. The print-out is made by a commercial x-y-recorder which is also used for recording the impedance test results. During the automatic tone decay test the patient himself increases the intensity of the tone only until he can hear the tone again, the intensity of the tone otherwise remaining constant. Thus, we obtain either a flat (adaptation) or a sharply declining (auditory fatigue) curve which correlates with the Békésy continuous tone curve, but may show a distinctive separation. The tone decay test is — in contrast to all other suprathreshold tests — independent of the amount of hearing loss. It can therefore give information on the kind of hearing impairment for normal short duration thresholds as well.