Normative findings of electrically evoked compound action potential measurements using the neural response telemetry of the Nucleus CI24M cochlear implant system.

One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T- and C-levels appeared to be moderate, in the range of 0.5-0.6.

The results in patients implanted with the nucleus double array cochlear implant: pitch discrimination and auditory performance.

OBJECTIVE: In patients with total or surgically inaccessible cochlear obliteration, only a reduced number of active electrodes can be inserted with standard cochlear implants, resulting in below average auditory performance. Therefore, a special implant with two electrode arrays was developed on the basis of the Nucleus 22 cochlear implant, the socalled Double Array. One electrode array with 11 active electrodes is inserted into the basal turn of the cochlea, while the second array with 10 active electrodes is inserted into the second turn. The Double Array is now available on the basis of the more advanced Nucleus 24 with 11 active electrodes on each array and two reference electrodes, one at the case and the second one an additional ball electrode, which is placed under the temporalis muscle. For device description and surgical technique see Lenarz et al. (2001). This paper presents psychophysical data on pitch discrimination and auditory performance of patients implanted with a Double Array on the basis of the Nucleus 22. STUDY DESIGN: A prospective intra-individual study using a Latin square paradigm was performed in six adult patients with obliterated cochlea who received the Nucleus 22 Double Array. After appropriate fitting and loudness balancing, patients were tested either with the basal, the apical or both electrode arrays. Apart from auditory performance tests including numbers and monosyllable word tests, pitch discrimination was determined with a defined procedure. RESULTS: When activating each array alone, auditory performance was better with the basal array than with the apical array. Both arrays together showed marked improvement compared with the basal array, indicating an additional effect of the second array. Pitch discrimination was significantly better for the electrodes in the basal turn than in the second turn, indicating differences in electrical excitation of the auditory nerve fibers. Pitch discrimination was positively correlated with auditory performance data. CONCLUSION: The additional apical array leads to significant improvement in auditory performance in patients with obliterated cochleae by increasing the number of intracochlear electrodes. Despite reduced pitch discrimination, the apical array provides important information for speech recognition. For this reason the Double Array provides a profound advantage for patients with obliterated or surgically inaccessible cochleae.

A force transducer for measuring mechanical properties of single cardiac myocytes.

We have described a transducer design capable of recording forces generated by single cardiac myocytes with sufficient temporal resolution to detect force responses to rapid length changes. Our force sensors were made from thin steel foils that act as cantilevers whose bending is monitored by reflection off a laser beam. Deflection of the laser beam is measured by a differential photodiode detector. A small, 50-micron-thick tungsten needle attached to the free end of the steel foil allowed us to glue single cardiac cells to the force transducer. The transducers have compliances of approximately 0.02 m/N and resonance frequencies between 2 and 3 kHz. The resolution is approximately 18 nN rms at a detector bandwidth of 16 kHz, so we were able to resolve 0.2% of the maximum isometric force ( approximately 12 microN) developed by a single cardiac myocyte. We have demonstrated that the transducer is well suited to analysis of mechanical properties of single ventricular myocytes, for example, the recording of isometric forces and rate constants of force redevelopment after rapid release-restretch maneuvers.

Surgical treatment of hidradenitis suppurativa of the axilla.

We review our surgical experience with hidradenitis suppurativa of the axilla at Cook County Hospital during the years 1963 to 1972. The operation for this entity described by Pollock et al has (1) reduced the length of hospitalization, (2) increased the rate of primary healing and reduced the period of secondary healing, (3) allowed a great amount of tissue to be excised, (4) permitted both axillae to be operated on at once (without incapacitating the patient), (5) avoided the need for skin grafting, and (6) has had less morbidity for those patients in whom primary healing is not achieved. We believe the method reported by Pollock et al is now the treatment of choice for this disease.