Comparison of two cochlear implantation techniques and their effects on the preservation of residual hearing. Is the surgical approach of any importance?

The goal of this work was to review the pre-and postsurgical auditory thresholds of two surgical implantation techniques, namely the mastoidectomy with posterior tympanotomy approach (MPTA) and suprameatal approach (SMA), to determine whether there is a difference in the degree of preservation of residual hearing. In a series of 430 consecutive implanted patients 227 patients had measurable pre-operative hearing thresholds at 250, 500, and 1,000 Hz. These patients were divided into two groups according to the surgical technique that was used for implantation. The SMA approach was followed for 84 patients in Amsterdam, whereas the MPTA technique was adhered to 143 patients in Maastricht. The outcome variables of interest were alteration of pre-and postoperative auditory thresholds after cochlear implantation. Complete or partial preservation of residual hearing was obtained in 21.4 and 21.7% in the SMA and MPTA group, respectively. No statistical differences could be found between the SMA and MPTA group (p = 0.96; Chi-square test). The SMA technique is correlated with a similar degree of hearing loss after cochlear implantation compared to the MPTA technique. However, both techniques were not able to conserve a measurable amount of hearing in patients with a substantial degree of residual hearing. Therefore, both surgical techniques need to be refined for patients in which residual acoustical hearing is pursued.

Measuring spectral and temporal resolution simultaneously: a comparison between two tests.

OBJECTIVE: Spectral- and temporal-resolution tests are seldom used in clinical practice despite their proven relevance for patients' speech understanding in noise and expected importance for hearing-aid fitting. The aim here was to investigate and compare two clinically applicable tests ('tone test' and 'sweep test') that measure both spectral and temporal resolution simultaneously. DESIGN: Experiments were conducted monaurally via headphones. After examining test-retest reliabilities and learning effects we compared results from tone and sweep tests to results from conventional spectral and temporal-resolution tests and to speech perception in noise scores. STUDY SAMPLE: A group of five normal-hearing listeners (aged 18-42 years, median 19) and 15 (sensorineurally) hearing-impaired listeners (aged 20-68 years, median 56). RESULTS: It was found that the tone test corresponded much better to the conventional methods than the sweep test. Relating spectral and temporal-resolution results to speech perception in noise scores showed that the tone test seems to be slightly more relevant for speech perception than the sweep test. CONCLUSIONS: It can be concluded that the tone test (after modifications we suggest, based on our findings) is a fast and reliable test that is suitable for measuring spectral and temporal resolution in a clinical setting.

Interactive fitting of multiple algorithms implemented in the same digital hearing aid.

The main purpose of this study is to examine the applicability of an adaptive and interactive optimization strategy to fine-tune three hearing-aid algorithms simultaneously: dynamic compression, temporal signal enhancement, and noise reduction. The optimal combination of these three algorithms was determined by a multidirectional pattern search with an adaptive step size. Additionally, we applied a round-robin procedure to validate the results of the optimization procedure. For both procedures the listeners were asked to compare two consecutive, differently processed sentences in continuous and fluctuating background noises on speech intelligibility. Ten hearing-impaired and four normal-hearing subjects participated. The reliability and consistency of the multidirectional pattern search was low, especially for the fluctuating noise condition. The results of the round-robin procedure did not correspond closely with the pattern search results. These findings suggest that the current implementation of a multidirectional optimization procedure has not yet proven to be applicable for the necessary individual fine tuning of complex signal processing strategies, when the objective is to maximize speech intelligibility.