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B J Gantz

Publications and source records attributed to B J Gantz.

At least 91 records · Page 5Linked to original sources
PubMed1987

Hearing results after cholesteatoma surgery: the Iowa experience.

This study compared the hearing outcome of canal-up and canal-down mastoidectomies for removal of cholesteatoma in 455 ears. An intact canal wall procedure was performed in 92 patients while the remainder (N = 363) underwent a canal-down operation. The hearing results for both procedures are dependent on the presence of the stapes superstructure. When the stapes superstructure was intact, 52% of the patients with canal-up operations had an air-bone gap of less than 20 dB. The corresponding figure for canal-down cases was 37%. When there was no stapes superstructure, 54% of the canal-up cases and 19% of the canal-down cases obtained a similar ABG closure. Preserving the posterior external auditory canal wall results in slightly better hearing function. However, when the stapes superstructure is intact, the difference in hearing function is not remarkable, and must be weighed against the potential for residual disease or recurrence associated with canal-up procedures.

Auditory Threshold↗
PubMed1986

Previous experience as a confounding factor in comparing cochlear-implant processing schemes.

It is of great importance to compare the relative merits of different cochlear-implant speech-processing strategies. Some groups have compared different strategies within single subjects, but usually the subject has prior experience with one strategy, and no allowance is made for this prior experience. We show in the present study that this is inappropriate. We tested one subject using the Melbourne (Cochlear Corp.) multichannel implant with the device set to process sounds in two different ways. In the first processing scheme, the device functioned normally, extracting information about voicing frequency, amplitude and second-formant frequency. This information activated the 21-channel device, determining pulse rate, pulse amplitude and electrode position (respectively). In the second processing scheme, a single electrode (with the largest dynamic range) was activated. This electrode coded overall amplitude and voicing frequency. The subject was tested on an audiovisual test of a 14-choice consonant recognition in the form /iCi/ over a period of over 4 months. During this time the subject used the 21-channel processor outside of the laboratory. Upon initial connection, there was little difference between the results obtained with the two schemes when tested in sound alone or in sound plus vision. However, after about 4 months, scores obtained with the 21-channel processor in sound plus vision were superior to the scores obtained with the one channel. This advantage came from a superiority in the features of voicing and nasality, but not place. Scores for sound-alone conditions between the two processing schemes remained similar for the 4-month period.(ABSTRACT TRUNCATED AT 250 WORDS)

Auditory Threshold↗
PubMed1985

Transient sensorineural hearing loss after overuse of portable headphone cassette radios.

Noise-induced sensorineural hearing loss has been associated with industry for many years. One conservative estimate suggests that 10 million Americans may have industry-related, noise-induced hearing loss. Acoustic trauma from any source, whether associated with work or recreations, is detrimental to hearing. The Occupational Safety and Health Administration has set industrial standards for noise levels, with current standards limiting noise exposure to 95 dBA for 2 hours daily. To date, however, there are no recreational standards. Many portable headphone cassette radios produce peak outputs of more than 100 dBA. Temporary threshold shifts could result from listening levels near the maximum output. Permanent sensorineural loss may result with repeated exposure. A pilot study was conducted in which 16 volunteers listened to headphone sets for 3 hours at their usual maximum level. Six volunteers showed transient shifts of 10 dB, and one volunteer showed a transient shift of approximately 30 dB. These shifts returned to normal within 24 hours. As expected, transient shifts frequently occur with recreational use. Therefore, recreational warnings and standards should be established.

Auditory Fatigue↗
PubMed1985

Iowa cochlear implant clinical project: results with two single-channel cochlear implants and one multi-channel cochlear implant.

Cochlear implants have become a realistic alternative for the management of profoundly deaf patients. A variety of implants with differing electrode designs and coding strategies have been developed by nine major implant centers around the world. Each center has their "star" patient, but objective comparisons between these different implant designs are unavailable. In order to determine the performance characteristics of the present generation of cochlear implants, comparison data are vital. We have developed an independent center where uniform objective comparisons of different cochlear implants can be performed longitudinally. This report will present results of nine patients implanted with three different cochlear implant prostheses. Four patients have been implanted with the Los Angeles (House) single-channel implant, three patients have received the Vienna (Hochmair) single-channel intracochlear device, and two patients have been implanted with the Melbourne (Clark) 21-channel unit. All patients have had 11 months or more of experience with their cochlear prostheses. The results of a comprehensive audiologic battery which includes audiovisual and environmental tasks are presented. All implants provide significant improvement in speechreading and sound awareness. The findings to date suggest that there is strong correlation between top-down cognitive processing (as reflected by lip reading skills) and performance with cochlear implants.

Adult↗
PubMed1985

Cochlear implant comparisons.

The implantation of an electrode into the cochlea of profoundly hearing-impaired adults now promises to be a viable alternative for rehabilitation. In this article we describe six different kinds of cochlear implants, the single-channel devices developed in Los Angeles, Stanford, and Vienna, and the multichannel devices developed in Melbourne, San Francisco, and Utah. We then present results from our own patients implanted with the Los Angeles, Vienna, and Melbourne cochlear implants. All systems provide information about environmental sounds and prosody, which can improve lip-reading ability. Only our patients implanted with the Melbourne system have been able to recognize words in unknown sentences, although others have reported such spectacular performance with single-channel devices. We stress the importance of recorded tests, of material that is unfamiliar to the patient, and of avoiding multiple presentations of the test material.

Audiometry, Speech↗
PubMed1985

Intraoperative facial nerve monitoring.

Intraoperative evoked electromyography is an effective tool for use in locating the position of a normal facial nerve or the site of a nerve conduction block in acute facial paralysis. The technique of intraoperative evoked electromyography is described. Intraoperative stimulation of the facial nerve is a more accurate method of identifying a nerve conduction block than the site-of-lesion Schirmer's test.

Electric Stimulation↗
PubMed1984

Initial Iowa results with the multichannel cochlear implant from Melbourne.

Two subjects who use the Melbourne multichannel cochlear implant were studied. Live-voice word, consonant, and vowel recognition tests, and a speech-tracking task were administered at regular intervals during the first 90 days after implantation. Results indicated 30-50% correct recognition of vowels (given 9 alternatives) and about 30-60% correct recognition of consonants (given 12 alternatives). Speech tracking showed from two to three times faster rates with the implant and vision compared to a vision-alone condition. After 3-4 months of implant experience, a number of recorded tests from the Minimal Auditory Capabilities battery and the Iowa Cochlear-Implant tests were then administered. These results indicated about 80% recognition of everyday sounds in a five-choice closed-set condition and about 50% recognition of everyday sounds in an open-set condition. The subjects were 50% correct at identifying the accented words in a sentence and about 50% correct at determining the number of syllables in a word. One subject was unable to recognize a sentence as a statement or a question. Background noise (+10 dB S/N) reduced their performance on a four-choice spondee test to chance. Both subjects were able to identify a sound as either a voice or a modulated noise at 95% correct, and both could recognize speaker sex at 95% correct. Neither could discriminate whether two (successive) sentences were spoken by the same speaker or by two different speakers. Remarkably, one subject identified 45% and the other 85% of the words in sentences that were preceded by a contextual picture using sound alone. One subject identified 13% of the words in sentences in sound alone even without contextual information.

Adult↗
PubMed1984

Preliminary assessment of the Los Angeles, Vienna and Melbourne cochlear implants.

We tested four patients using the single-channel cochlear implant from Los Angeles, three patients using the single-channel cochlear implant from Vienna, and two patients using the multichannel cochlear implant from Melbourne. Tests from the MAC battery and the Iowa Cochlear Implant Battery were used. Most patients were able to identify some environmental sounds. Three of the patients had difficulty distinguishing between male and female voices, and three could not distinguish between a noise and a voice. All patients had difficulty discriminating between unknown speakers of the same sex. A four-choice spondee test in noise showed that all patients suffered drastically from background noise. In all cases there was an improvement in lipreading ability with the implant. On a sentence test with a contextual cue seven patients got some words with sound alone. Results obtained with the multichannel implant are superior on several tasks, but we have tested too few patients to allow us any firm conclusions.

Auditory Perception↗
PubMed1983

Modified transotic approach to the cerebellopontile angle.

A modification of the transotic approach to the cerebellopontile angle involves complete removal of the otic capsule bone, obliteration of the middle ear cleft, and removal of the posterior external auditory canal wall, while leaving the fallopian canal intact. The major advantage of this technique is that it allows more direct visualization of the most vulnerable portion of the facial nerve medial to the anterior wall of the internal auditory canal during acoustic tumor removal.

Cerebellopontine Angle↗
PubMed1982

Differential diagnosis and management of the dizzy patient.

Much diagnostic confusion arises from the fact that dizziness is a vague symptom with multiple individual interpretations. A systematic approach to eliciting a history from a dizzy patient is presented, differential diagnoses of vertigo are delineated, and appropriate treatment for peripheral labyrinthine disorders is suggested.

Cerebellar Neoplasms↗
PubMed1982

Ultrastructural evaluation of biochemical events of bone resorption in human chronic otitis media.

Bone resorption is a significant component of chronic inflammatory ear disease. Bone is a unique tissue requiring both demineralization and collagen degradation for breakdown. Mineral removal probably occurs prior to collagen destruction. A localized change in pH may be one of the mechanisms that induces demineralization. Localized accumulations of lysosomal acid hydrolases could provide the acidic environment necessary for mineral removal. The present study utilizes the electron microscope to localize the lysosomal enzyme acid phosphatase in specimens removed from patients with chronic otitis media. Areas of localized bone resorption exhibited mononuclear inflammatory cells attached to the resorption margin. These cells contained abundant acid phosphatase, as did isolated fibroblasts within the zone of inflammation at the resorption margin. Extra cellular acid phosphatase was seen in these areas. Within the bone, osteocytes adjacent to resorption displayed increased cytoplasmic organelle patterns and contained the acid phosphatase reaction. The localization of destructive enzymes in mononuclear inflammatory cells and osteocytes explains the bony destructive changes observed in human chronic otitis media in the absence of multinucleated osteoclasts.

Acid Phosphatase↗
PubMedDate not supplied

Intraoperative evoked electromyography in Bell's palsy.

The technique of intraoperative evoked electromyography is described in detail. Direct intraoperative stimulation of the exposed facial nerve identified the sites of nerve impulse conduction blocks in 16 of 18 patients who needed decompression for Bell' s palsy. In order to determine the site of impulse conduction block the test must be performed before 100 per cent nerve degeneration occurs. The lesions extended only a few millimeters and were found to be proximal to the geniculate ganglion in 15 (94 per cent) of these patients. Schirmer's test correctly identified the sites of the lesions in only 61 per cent of the patients. To locate the precise site of the lesion inducing a conduction block in Bell's palsy, intraoperative evoked electromyography must be used. The limited extent of the blocked motor fibers indicates that segmental rather than total intratemporal decompression is needed in Bell's palsy.

Electromyography↗
PubMedDate not supplied

Cartilage reconstruction of the scutum defects in canal wall up mastoidectomies.

PURPOSE: This study was performed to evaluate whether cartilage reconstruction of scutal wall defects diminishes retraction pocket and recurrent cholesteatoma, as compared with no cartilage reconstruction of the scutal defect. MATERIALS AND METHODS: A retrospective chart review from 1980 to 1993 was performed on all patients undergoing a canal wall up mastoidectomy. These procedures were done in a large teaching hospital where some surgeons reconstructed with cartilage and others did not. The recurrence rate of cholesteatoma and retraction pockets, as well as the need for further surgery, was assessed. RESULTS: There were 103 canal wall up mastoidectomies performed, and 84 patients were available for long term follow-up. Of these, 52 were not reconstructed with cartilage, whereas 32 were reconstructed with cartilage. Of the 52 patients not reconstructed, 47% did not develop retraction pockets. Of the 53% who did develop a retraction pocket, only one third required further surgery, and the others were managed in the office. Of the 32 patients that were reconstructed with cartilage, 66% did not develop further retractions. Of the 34% who did develop a retraction pocket, one third required further surgery. In both groups, those who did require further surgery did have recurrent cholesteatoma as well. CONCLUSION: It would appear that reconstruction of scutal wall defects after canal wall up mastoidectomies with cartilage may be of some benefit in preventing further retraction pockets and thus the recurrence of cholesteatoma.

Adult↗
PubMedDate not supplied

MR evaluation of acoustic schwannoma with fractional contrast doses.

OBJECTIVE: To investigate the utility of lower contrast medium doses for the detection and conspicuity of acoustic schwannomas. MATERIALS AND METHODS: The L/B (L, lesion; B, background) ratios or lesion contrast of 17 pathologically proven acoustic schwannomas studied with a standard dose (0.1 mmol/kg) of gadopentetate dimeglumine was measured. In addition, 22 patients with acoustic schwannomas were studied prospectively with fractional doses using the incremental dose technique. Each patient received an initial bolus injection of one-eight the standard dose (0.0125 mmol/kg) followed by an injection of one-eighth, one-fourth, and one-half the standard dose at 5 min intervals to achieve a cumulative dose of one-fourth, one-half and full dose, respectively. Imaging was performed immediately after each injection. RESULTS: Standard dose--The L/B ratios of pathologically proven acoustic schwannomas to mastoid air cells ranged from 14.8 to 41.2 (mean +/- SEM, 28.0 +/- 1.95), which were approximately 17 times more than those of intraparenchymal lesions. Fractional cumulative dose--Qualitative visual analysis demonstrated that all acoustic schwannomas showed apparent enhancement at one-fourth dose. Intense enhancement was noted at one-half and full dose. Quantitative analysis demonstrated the mean L/B ratios between the acoustic schwannomas and mastoid air cells of the precontrast and one-eighth, one-fourth, one-half, and full dose studies were 8.33 +/- 0.52, 11.21 +/- 0.75, 13.02 +/- 0.83, 15.38 +/- 0.98, and 18.03 +/- 1.36, respectively. CONCLUSION: The L/B ratios or lesion contrast of acoustic schwannomas at various fractional contrast medium doses was significantly higher compared with that of intraparenchymal lesions. Thus, the standard contrast medium dose may not be necessary for detection of acoustic schwannomas, and a fractional dose may be sufficient. Although the optimal fractional dose remains to be determined, one-half of the standard dose (0.05 mmol/kg) appears to be sufficient because of intense enhancement at this dose.

Contrast Media↗
PubMedDate not supplied

Epidermal Langerhans cells in cholesteatoma.

The function of the epithelial component of a cholesteatoma has been the subject of intense research. The epithelium does not appear to have proteolytic enzyme activity, yet when it is present, increased amounts of bone resorption occur. Recent evidence suggests that epidermal Langerhans cells within epithelium have an immunologic alerting function. These cells were identified in normal tympanic membranes, canal skin, and cholesteatoma. The Langerhans cells in cholesteatoma displayed morphologic features similar to a contact hypersensitivity state. Langerhans cells within the epithelial matrix of the cholesteatoma may be responsible for generating and maintaining the chronic inflammatory reaction which induces bone resorption in this disease.

Cell Count↗
PubMedDate not supplied

Electroneurographic evaluation of the facial nerve. Method and technical problems.

Electroneurography (ENoG) is emerging as a useful clinical tool in evaluation of acute facial nerve paralysis. The method of test performance can have an influence on the test results. This paper describes in detail the method used to perform ENoG at the University of Zurich. The variables that affect the results and methods of avoiding technical problems are emphasized. If ENoG is to be used clinically, the examination should be performed in a manner similar to that described in reports from this institution.

Action Potentials↗