The Groningen, Nijdam and Pro vox voice prostheses (VP) are all low-pressure, indwelling voice prostheses. Although there are differences concerning the valve mechanism, they have a similar design and are therefore interchangeable, in a prospective study, 845 consecutive replacements were evaluated in 158 patients, Average device lifetime differed significantly from 13 weeks for the Provox VP and 15.8 weeks for the Groningen VP, to 19 weeks for the Nijdam device. Leakage through or around a voice prosthesis was the main replacement indication. Leakage occurred significantly more often with the Provox VP (80,2%) than with the Groningen VP (58.8%) or the Nijdam VP (55%). Increased airflow resistance as a replacement indication occurred significantly more often with the Groningen VP (45,4%) and the Nijdam VP (45.9%) than with the Provox VP (22.7%). Complications during the replacement procedure were rare and usually mild. Replacement was usually an easy outpatient procedure; general anaesthesia was only necessary in 3.0% of 845 replacements, without any significant di/fercnce between the three devices. Granulation tissue and hypertrophic scar tissue formation were the most frequent local complications. They occurred in less than 10% of our patients but were significantly more common in patients with a Nijdam VP.

In humans, the binaural interaction at the brainstem level has been studied for over 15 years. The binaural interaction component (BIC) is obtained by subtracting the summed auditory brainstem response (ABR) in the monaural stimulus mode from the ABR obtained in the binaural stimulus mode. By nature of this subtraction process, the signal-to-noise ratio of the difference waveform is poor, requiring an objective detection criterion to decide whether a significant BIC is present. In this study, the effectiveness of two analysis methods was compared. The first method is the "3 SD' method, which is based on a signal-to-noise evaluation. The second method is a template matching method, in which templates are derived from normal hearing subjects' responses and individual responses are cross-correlated with these templates. The templates were allowed to shift over a range of -0.8 to 0.8 ms in search of the maximum correlation coefficient. Thirty-nine subjects with normal hearing and five patients with a unilateral profound hearing loss participated in the study. ABRs were obtained with rarefaction and condensation clicks at a rate of 15/s and a level of 70 dB nHL. Latencies of the ABR waves I, III and V for all normal hearing subjects and for the normal ear of the patients were within the normal range. The efficiencies of both methods, defined as the number of normal hearing adults with a significant BIC plus the number of patients without a significant BIC divided by the total number of subjects, were determined. The results show that the "3 SD' method is superior to the template matching method: the efficiencies were 95% and 70% respectively, when responses to rarefaction and condensation clicks were taken together. With the "3 SD' method, a significant BIC is demonstrated in almost all normal hearing subjects (97%). However, the "3 SD' method also falsely indicated a significant BIC in one patient. These results suggest that the BIC may have clinical value in studying binaural interaction in humans.

The cases of 3 patients who had 'perilymph gushers' following stapes surgery are reported. The similarities in their clinical histories and examinations are discussed. All 3 were males and had progressive mixed deafness presenting in early childhood. Polytomography revealed anomalies in both the vestibule and internal auditory meatus in 1 patient; the stapedial reflex was unexpectedly large in all 3. Further preoperative evaluation of these features in other patients and patients affected by the X-linked deafness syndrome is indicated in order to assess the validity of the above criteria.

Three siblings with Cockayne's syndrome are reported. Sural nerve biopsies revealed segmental de- and remyelination with onion-bulb formation. Disturbed visual and brain-stem auditory evoked responses indicated demyelination of the central nervous system. The peripheral and central myelinopathy increased with age, suggesting a progressive disorder. Our observations support the theory of Cockayne's syndrome being a leukodystrophy.

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