Recent results with the MED-EL COMBI 40+ cochlear implant and TEMPO+ behind-the-ear processor. (Original Article).

Abstract

Cochlear implantation is a viable treatment for patients with severe to profound hearing loss. We report the results of speech perception tests (numbers, monosyllables, and sentence tests) achieved with MED-EL's COMBI 40+ (C40+) cochlear implant after 12 months of use. These findings, which were taken from a larger German study, were similar to those of other studies of the C40+ implant. We also compared the differences in speech perception observed with the CIS PRO+ body-worn speech processor and the newer TEMPO+ behind-the-ear speech processor. Although these results were similar with respect to most of the measured parameters, the TEMPO+ processor had a distinct advantage during tests in noise.

Introduction

Cochlear implant surgery is now recognized as the standard treatment for severely to profoundly hearing-impaired adults and children. (1-8) Since 1996, >6,000 MED-EL COMBI 40+ (C40+) cochlear implants have been placed in patients at more than 260 clinics in 54 countries. In the United States, the federal Food and Drug Administration approved the use of this device in both adults and children in August 2001.

The C40+ is a 12-channel cochlear implant that features high-rate pulsatile stimulation. Symmetric biphasic current pulses can be generated up to a maximum repetition rate of 18,180 pulses per second. Stimulation signals are delivered via a monopolar intracochlear multichannel electrode. (9) The C40+ has replaced the company's earlier product, the COMBI 40 (C40) eight-channel implant.

The C40+ has been investigated in studies in many countries, and speech perception results have been promising. For example, a study of three cases in Russia revealed that C40+ users experienced appreciable progress in hearing during speech discrimination tasks, as well as an improvement in speech production. (10) A study in Vienna demonstrated that C40+ users were experiencing a continuous improvement in speech perception 3 years following implantation. (7) The same Viennese team also compared speech perception scores in noise among C40+ users with those achieved by a similar group of hearing aid users and found that the implant users recorded higher scores. (11) In that study, all C40+ users obtained substantial benefit from their implants in noise, even at a signal-to-noise ratio of 15 dB.

The aforementioned studies were conducted on patients who used the body-worn CIS PRO+ speech processor. In 1998, MED-EL introduced a new speech processor: the TEMPO+ (figure 1). This was the firm's first ear-level speech processor capable of using high-rate stimulation (18,180 pulses/sec), continuous interleaved sampling (CIS+), and the Hilbert transformation for envelope extraction. The TEMPO+ processor also allows for an upward extension of the analyzed frequency range (200 to 10,000 Hz), (12) which has been shown to improve consonant understanding in quiet. (13,14) The function of the Hilbert transformation is to improve sound quality by allowing for a more accurate determination of the signal envelope providing loudness-over-time and pitch information. (15,16)

Initial studies showed that patients who used the TEMPO+ had significantly higher Freiburger monosyllable word scores than did those who used the CIS PRO+. (12) TEMPO+ users also reported a significantly greater improvement in telephone use over time, sound quality, and their ability to enjoy music. In a subjective questionnaire, the vast majority of patients reported that speech understanding with the TEMPO+ was equal to or better than that experienced with CIS PRO+, and they rated the sound quality of the TEMPO+ as higher.

In this article, we report the results of a study of the C40+ implant. We also compare initial results among those patients who switched from using the CIS PRO+ to the TEMPO+ speech processor.

Patients and methods

Patients. A total of 42 patients--22 men and 20 women, aged 20 to 72 years (mean: 52 yr, 9 mo)--were available for assessment at 12 months. Their duration of deafness ranged from 1 month to 31 years (mean: 8 yr, 7 mo). Of this group, 22 patients had progressive hearing loss, five had sudden hearing loss, and one had hereditary hearing loss. Other etiologies included otosclerosis (4 patients), meningitis (2 patients), sepsis (1 patient), and skull fracture (1 patient). The other six patients had hearing loss of unknown etiology.

Methods. Testing was conducted at German-language cochlear implant clinics in Austria, Germany, Switzerland, and Italy. A battery of tests was used to assess speech recognition. The Freiburger numbers test and the Freiburger monosyllables test were recorded on and played from a Westra CD No. 1. The HSM (Hochmair-Desoyer/Schulz/Moser) sentence test, (17) played on a compact. disc, was used under five CCITT noise conditions--in quiet and at 15, 10, 5, and 0 dB--to assess auditory skills under conditions that more resemble everyday listening situations. All tests were conducted in a random order.

Statistical analysis. The comparison of the CIS PRO+ and TEMPO+ results had to be made on a somewhat superficial level because the number of new TEMPO+ users was still too small to allow for a valid statistical analysis.

Results

Preoperatively, all patients underwent a baseline assessment of their hearing, and all were then assigned a baseline score of 0. After 12 months, results were tabulated for all C40+ users as a group (table). Furthermore, results were also classified according to the type of speech processor each patient used. Overall, there appeared to be little difference in test scores between the two speech processor groups, although there did appear to be some advantage in favor of the TEMPO+ during tests in noise (figure 2). Even at a very difficult signal-to-noise ratio of 0 dB, the TEMPO+ users scored 6.8% higher than did the CIS PRO+ users.

Discussion

In earlier 12-month studies of the C40 (the predecessor of the C40+), mean speech understanding (monosyllables) scores in quiet ranged from 40.7 to 54.5%. (5,18) Our analysis found that the mean percentage of correct answers among patients who used the C40+ for 12 months was slightly higher at 58.0% (table). Likewise, the mean sentence recognition score in silence seemed to be slightly higher among C40+ users (94.9%) than among C40 users (89.0%), (5) but a definitive conclusion cannot be drawn because the data available for this comparison were too limited. In another study comparing the C40+ with the C40 (an extensive data analysis involving more than 120 patients), no essential difference in speech recognition in quiet was noted between the two groups. (19) Nevertheless, the C40+ has two unequivocal advantages over the C40. The C40+ has more channels (12 vs 8), which allows for greater flexibility in programming. It also has a thinner ceramic case, which makes it far more suitable for young and very young c hildren.

Our comparison of the CIS PRO+ and TEMPO+ speech processors found that differences were minimal, except in increasingly difficult noise conditions, where the TEMPO+ was more effective. However, further data are needed to support these findings because they might have been influenced by the extended frequency range and the Hubert transformation used in the CIS+ speech coding strategy.

[FIGURE 2 OMITTED]

Table

Speech perception tests results (%)

                          Cochlear implant         Speech processor

Test                       All C40+ users   CIS PRO+ users  TEMPO+ users

Freiburger numbers              94.9             94.9           95.0
Freiburger monosyllables        58.0             58.1           57.3
HSM in quiet (*)                76.9             76.6           78.9
HSM at 15 dB SNR (+)            55.6             55.5           56.4
HSM at 10 dB SNR                38.2             35.4           55.2
HSM at 5 dB SNR                 14.4             12.8           19.3
HSM at 0 dB SNR                  4.6              3.6           10.4

(*)HSM = Hochmair-Desoyer/Schulz/Moser sentence test.

(+)Signal-to-noise ratio.

Acknowledgments

Test administration and data collection were carried out by personnel at the clinics listed here, and we sincerely thank them for their valuable assistance. Austria: Universitatsklinik fur Hals-Nasen-Ohren-Heilkunde, Wien; Klinik fUr Hals-Nasen-Ohren-Heilkunde, Landeskrankenanstalten, Salzburg. Germany: Klinik fur Kommunikationsstorungen, Mainz; Klinik rechts der lsar, Munchen Klinikum Grosshadern, Munchen Universitats-Hals-Nasen-Ohren-Klinik, Wurzburg; Klinik fur Hals-Nasen-Ohren-Heilkunde, Tubingen; Klinik fur Hals-Nasen-Ohren-Heilkunde, Magdeburg; Klinik fur Hals-Nasen-Obren-Heilkunde, Dresden; Klinik fur Hals-Nasen-Ohren-Heilkunde, Bochum; Klinik fur Hals-Nasen-Ohren-Heilkunde, Frankfurt. Switzerland: Universitats-HNO-Klinik, Bern; Inselspital, Bern; Klinik fur Hals-Nasen-Ohren-Heilkunde, Luzern. Italy: Klinik fur Hals-Nasen-Ohren-Heilkunde, Bozen.

References

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From the Clinical Research Department, MED-EL, Innsbruck, Austria.

Reprint requests: Ilona Anderson, Clinical Research Department, MED-EL, Furstenweg 77, Innsbruck 6020, Austria. Phone: [phone]; fax: [phone]; e-mail: i.anderson@ medel.com