Analysis of streptomycin-resistance of Escherichia coli mutants.

We previously reported about Escherichia coli transformation experiments yielding streptomycin-resistant cells carrying a C912 to T transition in a plasmid-born 16S rRNA gene. These experiments were based on results obtained with streptomycin-resistant Euglena chloroplasts bearing an equivalent mutation in the single chloroplast 16S rRNA gene. We extended this study and transformed E. coli with plasmid constructs having a mutated 16S rRNA gene at position 914 (A to C) or a double mutation at positions 912 and 888 (C to T:G to A) or a mutation in the S12 gene (Lys-42 to Thr). We tested the transformed cells before and after a screening procedure in the presence of streptomycin. We find that the plasmid-born mutations protect colonies against a short streptomycin exposure, but ribosomes carrying mutated 16S rRNA do not significantly reduce codon misreading in vitro. However, ribosomes isolated from transformed cells after the screening procedure resist misreading. These ribosomes have acquired a second mutation in the S12 protein as shown in one case by sequencing and by transformation experiments. Furthermore, we show that the A914 to C mutation prevents (strongly reduces) base methylation in the central domain of 16S rRNA.

Activation of the auditory cortex by cochlear stimulation in a deaf patient.

We have recorded cerebral electric and magnetic responses to electric stimulation of the auditory nerve in a deaf patient with multichannel cochlear prosthesis. The electric response peaked with a vertex-negative deflection at 65 ms. Clear magnetic responses, coinciding with the vertex potential, were obtained only over the hemisphere ipsilateral to the stimulation; the field pattern indicated activation of the auditory cortex within the Sylvian fissure. The results suggest modification of the central auditory pathways in this patient deaf from early childhood.

Binaural interaction in a cochlear implant patient.

Binaural interaction was demonstrated in electrically evoked brainstem responses (EBRs) of a bilaterally implanted patient. A clear binaural difference waveform (BD), consisting of a negative peak near 3.6 ms followed by a positive peak near 4.4 ms, was found by subtracting the recordings with diotic stimulation from the sum of the recordings with monotic stimulation. These results are consistent with those reported for normal subjects and suggest that neural processing in this patient might resemble those ordinarily used in binaural hearing. They strengthen the argument that EBRs in cochlear implant patients do result from activity in auditory brainstem neurons and suggest a method for aligning the positions of the intracochlear electrodes.

Treatment of endolymphatic hydrops with cochleosacculotomy. Clinical results and experimental findings.

Cochleosacculotomy was performed on 25 patients with Meniere's syndrome. Long-term relief of vertigo was obtained in 19 out of 23 (82%). Postoperatively dead ears occurred in three cases. The same operation was performed on 12 guinea pigs in which hydrops had been surgically induced by blockage of the endolymphatic duct and sac. All fistulas were healed and cochleosacculotomy did not decrease or prevent the induced endolymphatic hydrops in these animals. Although histologic confirmation of persistent fistulas in human ears is lacking, the relief of vertigo in patients may not be caused by "drainage" but, rather, by a nonspecific effect on the inner ear. Cochleosacculotomy gives results comparable with other nondestructive surgical procedures performed to suppress vertigo in Meniere's syndrome.

Intracochlear potential distribution with intracochlear and extracochlear electrical stimulation in humans.

Intracochlear potential distributions were measured from subjects implanted with the Ineraid multichannel cochlear implant. The electrode array provided direct accessibility for obtaining measurements. Different modes of stimulation were used. The findings with intracochlear monopolar stimulation seem to confirm that significant low-resistance pathways, in which currents can flow into or out of the cochlea, are located in the basal turn. The results with extracochlear stimulation only show small intracochlear potential gradients. This finding suggests that no substantial currents flow along the auditory nerve fibers when extracochlear stimulation is used. These results concur with the electrically evoked auditory brain stem responses, in that intracochlear stimulation consistently elicited auditory brain stem responses, whereas responses elicited at or near the round window by extracochlear stimulation were weak or absent.

Indication of a relation between speech perception and temporal resolution for cochlear implantees.

In order to better understand the reasons for success or failure of a cochlear implant system for various patients, it appears necessary to analyze the patients' basic psychophysical capacities in relation to speech perception. Five patients with intracochlear multichannel Ineraid implants were studied in terms of their performance on temporal analysis in relation to their perception of consonants. For temporal analysis we measured the detection of a silent gap in noise and of an interval between two clicks. For consonant perception we established a confusion matrix based on 12 consonants presented in a vowel-consonant-vowel context using the vowel /a/. The results showed a correlation between temporal resolution for two successive clicks at the most basal cochlear electrode used, and the perception of place of articulation of consonants. This finding indicates that delivering fine temporal coding can be crucial for the success of an implant and that for a given subject, optimal capacity for temporal resolution may serve as a criterion for choosing a basal electrode.

Short- and long-term results of stapedotomy and stapedectomy with a teflon-wire piston prosthesis.

We analyzed the results of 604 cases of primary stapes surgery performed between 1974 and 1997 with replacement of the stapes by a 0.6- or 0.8-mm Schuknecht Teflon-wire piston. At long-term follow-up (1 to 21 years; mean, 7 years), the residual air-bone gap was 10 dB or less in 79% of the cases. The hearing results and postoperative complications were comparable to those reported by authors who used the same evaluation criteria. Although the aim of the surgery was to perform a small stapedotomy with a narrow footplate perforation (0.8 mm), a large stapedotomy or a stapedectomy was performed in 134 cases (22.2%) because of surgical or anatomic conditions. Our results show that the larger footplate perforations allowed a better correction of the air-bone gap at the lower frequencies. The ears with larger perforations did not show a higher incidence of sensorineural hearing loss.

Differential diagnosis of xerostomia by quantitative salivary gland scintigraphy.

A new and rapid method of quantitative salivary gland scintigraphy has been developed. The uptake of pertechnetate in the glandular tissue and in a reference area in the neck are measured. The ratio between these measurements gives an index of salivary gland activity. By using this activity index, quantitative information on the functional state of the parotid and submandibular glands can be obtained. In cases of xerostomia such measurements may be particularly helpful in differentiating Sjögren's syndrome and sialosis and hence in the choice of appropriate treatment.

Auditory-nerve potentials from ear canals of patients with otologic problems.

Summary--The feasibility of making rountine measurements of human auditory-nerve potentials in an office environment is demonstrated. Using a portable device for stimulus generating and response recording, auditory-nerve potentials are recorded from subjects with normal and abnormal hearing by means of an electrode placed on the skin of the ear canal. The results can be compared with those of others obtained under laboratory conditions. Preliminary results indicate that in many instances, the nature of the hearing deficit is related to the latency and size of the click-evoked auditory-nerve potentials. The precise relationships between nerve responses and specific disease conditions are still difficult to formulate.

Recording auditory-nerve potentials as an office procedure.

Recording auditory-nerve potentials from human subjects is already a routine procedure in the laboratory. In order to bring such recording capabilities into the office of practicing otologists, a number of difficulties had to be overcome. First, a small signal averager was built and incorporated into a stimulus generating and response recording system. The entire system was made portable and self-sufficient. The effects of electrical interference and background acoustic noise were shown to be tolerable. After studies of how responses vary with electrode location, electrodes were designed to be placed on the ear canal so that no invasive procedures were necessary. Methods were found to simplify the procedure so that recordings can be made in a matter of minutes by one person working alone.

Histopathology of cochlear implants in humans.

The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.

Clinical application of auditory nerve responses recorded from the ear canal.

The practicality of recording auditory nerve responses in the routine practice of an otologist is demonstrated. Such recordings are particularly useful when the course of treatment requires a distinction between central or peripheral disorders. They are also helpful when it is difficult to obtain a valid audiogram. The electrical recordings from the auditory nerve can, in combination with standard audiological, otological and neurological examinations, present a more accurate picture of the patient's condition.

Bilateral electrical stimulation of a congenitally-deaf ear and of an acquired-deaf ear.

Two identical multichannel intracochlear prostheses were implanted in the same patient. The first prosthesis, implanted in the congenitally-deaf right ear, elicited clear sound perception but no speech recognition. After 2 years, a second prosthesis, implanted in the acquired-deaf left ear, enabled the patient to understand speech without lip-reading. Brainstem and middle-latency evoked potentials were similar with electrical stimulation of both ears and resembled those evoked by acoustic stimuli in subjects with normal hearing. Cortical electric and magnetic responses differed for right- and left-sided electrical stimulation suggesting that stimulation of the congenitally-deaf ear elicited an abnormal activation of the auditory cortex. These results suggest that only cortical responses were affected by the different histories of deafness of the ears.

Cortical activity evoked by a multichannel cochlear prosthesis.

We have recorded electric potentials and neuromagnetic fields evoked by electric stimulation of the auditory nerve in a totally deaf patient with an implanted multichannel prosthesis. The evoked electric responses were a vertex-negative deflection at about 70 ms after stimulus onset and a vertex-positive deflection at about 180 ms. Evoked magnetic responses coinciding with the vertex potential were found in the right hemisphere, ipsilateral to the stimulated ear. The equivalent source of these responses corresponds to activation of the right auditory cortex. In the left hemisphere, the magnetic responses were considerably smaller and less reliable. These results suggest an abnormality of the central auditory pathways in this patient. In the future, neuromagnetic recordings might be used preoperatively to forecast the effectiveness of the possible implantation.

Auditory nerve and brainstem responses in the newborn and in preschool children.

The practicability of recording auditory nerve and brainstem responses during early childhood is demonstrated. This paper reports our experience with two different electrode locations: ear-canal/ear-lobe and ear-lobe/vertex. The test is performed with a light portable stimulus-generating and response-recording system that can easily be brought into wards and nurseries. In most instances, the presence of responses can be assessed using ear-lobe/vertex recordings. There is seldom any need for sedation or general anaesthesia. Testing personnel can be limited to one trained technician. If responses are not detected, ear-canal/ear-lobe recording may be used to clarify the results. General anaesthesia may then be necessary and the presence of a physician will be required for the placement of the canal electrode.

First field trials with a portable CIS processor for the Ineraid multichannel cochlear implant.

The continuous interleaved sampling (CIS) strategy is a promising sound processing strategy for multichannel cochlear implants which provides immediate improvements in speech recognition when tested on Ineraid users: patients with only a few hours of experience (in laboratory testing) with the CIS strategy score better than with the Ineraid prosthesis they used since they, were implanted. The goal of this study was to evaluate the benefits that can be gained by the use of the new strategy in every day life. Two patients, implanted with the Ineraid multichannel cochlear implant, were equipped with a portable numerical processor programmed to implement a high rate CIS strategy. Their speech recognition was evaluated periodically with consonant and vowel identification tests for more than 6 months of use. Tests were also made with the Ineraid processor during the same experimental sessions and patients were regularly interviewed about their experience. Performance with the portable CIS processor was superior or equal to that obtained previously in the laboratory with the same strategy. Both patients achieved the best scores in 6 years of cochlear implant use. Qualitative reports from the patients suggest that the CIS strategy can improve "hearing" performance of cochlear implant users in many important situations of every day life. Altogether, these results hold great promises for all users of the Ineraid multichannel cochlear implant.

Relevance of otopathological findings in the treatment of dizzy patients.

Dizziness is a common symptom in disorders of the brain and the ear. In a retrospective study of 1,000 cases, dizziness is attributed to a peripheral disorder in 25%, to a CNS disorder in 46%, and to undetermined causes in 29% of the cases. Peripheral disorders can be defined in terms of histopathological changes; the most frequent is cupulolithiasis, followed by endolymphatic hydrops and vestibular neuritis. These vestibular disorders are reviewed and discussed in connection with accepted facts and current hypotheses.

Multiple myeloma presenting with external ear canal mass.

The manifestations of multiple myeloma are protean and related to bony osteolytic lesions, and to medullar and renal insufficiency. We report a patient who presented with otalgia as the inaugural symptom of multiple myeloma. Local irradiation combined with systemic chemotherapy led to the disappearance of the temporal bone mass and the accompanying symptoms. To date, 24 months after the diagnosis, the patient is still in remission. The literature on otological involvement in multiple myeloma is reviewed. Symptoms are non-specific and include hearing loss, tinnitus, dizziness, facial paralysis, and otalgia. The diagnosis of multiple myeloma should be considered in the presence of a temporal bone mass.

[Surgical treatment of Ménière's disease by sacculotomy, cochleo-sacculotomy and transtympanic aerators]. / Traitement chirurgical de la maladie de Ménière par sacculotomie, cochléo-sacculotomie et aérateurs transtympaniques.

Sixty-two patients suffering from severe Ménière's disease with invalidating vertigo attacks were treated between 1976 and 1987 by three minoir surgical procedures: sacculotomy (19), cochleo-sacculotomy (15) or a transtympanic ventilation tube (28). The results were assessed after the second post-operative year according to the criteria of the American Academy of Otolaryngology (1985). The overall success rate for vertigo control was 79% with sacculotomy, 80 with cochleo-sacculotomy and 82% with transtympanic ventilation tubes. Severe permanent hearing-losses occurred in 20% after sacculotomy and cochleo-sacculotomy. Drop-attacks were not improved. These three surgical procedures give similar results with respect to vertigo control without any vital risk. The precise mechanisme of action in these procedures is not yet well understood.

[The "Ineraid" multichannel cochlear implant]. / L'implant intra-cochléaire multicanal "Ineraid".

In Geneva from 1985 to November 1990, we have implanted 21 Ineraid TM multichannel-cochlear implants in 18 totally deaf patients. On the basis of our experience we have divided the patients in 2 categories: optimal cases and difficult cases. Optimal cases had post lingual deafness and adequate anatomical conditions for implantation. They all recovered understanding of free running speech without lip-reading. Difficult cases had ossified cochlea or pre-and-perilingual deafness: results are variable and less predictable. The cochlear implant is both an artificial sense organ and a prosthetic device. With the aid of the prothesis the patient can hear. When the processor stops functionning the patient is again totally deaf. Implanted deaf patients require life-long technical and medical support.