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Biomedical subjects

M S Robinette

Publications and source records attributed to M S Robinette.

17 recordsLinked to original sources
PubMed2000

Auditory brainstem response and magnetic resonance imaging for acoustic neuromas: costs by prevalence.

OBJECTIVE: To compare hypothetical costs for identification of acoustic tumors when using magnetic resonance imaging with gadolinium Gd 64 (MRI-(64)Gd) as a sole diagnostic test and when using auditory brainstem response (ABR) testing followed by MRI-( 64)Gd (ABR + MRI-(64)Gd) for those with positive ABR findings. PATIENTS AND METHODS: Retrospective review of the medical records of 75 patients having surgically confirmed acoustic neuromas to categorize them into 3 subgroups relative to their risk of having a cerebellopontine angle tumor based on history, symptoms, and routine pure-tone and speech audiometric findings. Hypothetical costs associated with identification of patients with acoustic neuroma in each subgroup were calculated for MRI-(64)Gd alone and ABR + MRI-( 64)Gd. Auditory brainstem response sensitivity and specificity data for the 75 patients with acoustic neuroma and 75 patients without a tumor matched for hearing loss were applied to the hypothetical subgroups. Tumor size was considered also. SETTING: Tertiary care center. MAIN OUTCOME MEASURE: Comparison of costs for MRI-(64)Gd and ABR + MRI-(64)Gd. RESULTS: Fouteen patients with acoustic neuroma were assigned to the high-risk category (30% probability); 45 were in the intermediate-risk category (5% probability); and 16 were in the low-risk category (1% probability). Auditory brainstem response testing correctly identified 100% of the large tumors (>2.0 cm), 93% of the medium-sized tumors (1.1-2.0 cm), and 82% of the small tumors (<1.0 cm). The hypothetical costs for identifying 14 patients with acoustic neuroma among 47 patients in the high-risk category using MRI-(64)Gd would be $70,500; ABR + MRI-(64)Gd costs for the 13 patients identified by ABR would be $39,600. Hypothetically 900 patients would be tested to identify the 45 acoustic neuromas in the intermediate-risk category. Magnetic resonance imaging with (64)Gd screening would reach $1.35 million for this sample. Auditory brainstem response testing and MRI-(64)Gd would be $486,000, but 4 acoustic neuromas would be missed. For the low-risk subgroup MRI-6(4)Gd screening of 1600 patients to identify 16 acoustic neuromas would total $2.4 million; ABR + MRI-(64)Gd to identify 15 of them would be $787,500. In this sample of 75 acoustic neuromas, large tumors were more prevalent in the low-risk subgroup than in the high- or intermediate-risk subgroups. CONCLUSIONS: Decisions regarding assessment of patients at risk for acoustic neuromas must be made on a case-by-case basis. Use of ABR + MRI-( 64)Gd allows considerable savings when patients are in the intermediate- or low-risk subgroups. New MRI and ABR testing techniques offer promise for reducing costs.

Cerebellar Neoplasms↗
PubMed1997

Nonsurgical factors predictive of postoperative hearing for patients with vestibular schwannoma.

OBJECTIVE: The purposes of the study were to determine whether preoperative cochlear reserve as measured by evoked otoacoustic emissions (EOAE) as well as other hearing variables often associated with hearing preservation are correlated with hearing preservation after tumor removal and to determine whether any hearing variables are independent of tumor size as a predictor of hearing preservation. STUDY DESIGN: Preoperative audiologic data for 104 patients having vestibular nerve schwannomas removed via a retrosigmoid surgical approach were reviewed and subjected to factor analysis. SETTING: All patients were seen at the Mayo Clinic, Rochester, Minnesota. PATIENTS: The patient sample was divided into two groups based on hearing thresholds after surgery. Group I consisted of 73 ears without hearing preservation. The remaining 31 ears, group II, had preserved hearing (defined as average postoperative pure-tone thresholds < or = 85-dB HL for 0.5, 1, 2, and 3 kHz). MAIN OUTCOME MEASURES: Variables not predictive of hearing preservation were age, gender, tumor laterality, and cochlear reserve (EOAE). Variables predictive of hearing preservation were small tumor size, pure-tone hearing sensitivity, speech reception thresholds, word recognition scores, integrity of cochlear nerve (acoustic reflex thresholds, and auditory brain stem response [ABR] waveforms). RESULTS: A multivariate logistic regression analysis showed that only word recognition scores at 40-dB sensation level were independent of tumor size as a predictor of hearing preservation.

Acoustic Stimulation↗
PubMed1996

Effect of temperature elevation on rabbit cochlear function as measured by distortion-product otoacoustic emissions.

Low-intensity laser stapedotomy has been shown to produce temperature elevations of 3 degrees to 4 degrees C within the cochlea. This study investigates the effect of temperature elevations in this range on cochlear outer hair cell function by use of distortion-product otoacoustic emissions in rabbits. Using esophageal temperature monitoring, we compared 2f1-f2 distortion-product otoacoustic emissions over a range of frequencies (1806 to 8691 Hz) at rabbit normothermia, normothermia plus 3 degrees C, and normothermia after passive cooling. Cochlear temperature was found to exceed changes in esophageal temperature by as much as 1.2 degrees C. We found that a maximum of 3 degrees C elevation in esophageal temperature did not permanently impair outer hair cell function in the rabbit cochlea. Results of this study suggest that moderate changes in cochlear temperature, such as those produced by low-intensity CO2 and holmium-yttrium aluminum garnet lasers, may not produce irreversible thermal damage to the cochlear outer hair cells.

Animals↗
PubMed1995

Otoacoustic emissions in sudden unilateral hearing loss associated with multiple sclerosis.

Sudden unilateral hearing loss may result from etiologies affecting cochlea, eighth nerve, or more central auditory tracts. Two case studies are presented in which the measurement of otoacoustic emissions helped rule out outer hair cell cochlear pathology. In both cases, the final diagnosis was sudden unilateral hearing loss associated with multiple sclerosis (MS). For one case, the sudden hearing loss was the first clinically recognized presenting sign of MS.

Acoustic Stimulation↗
PubMed1989

Influence of dietary magnesium on the amplitude of wave V of the auditory brainstem response.

Thirty-six weanling guinea pigs were fed either a low (600 ppm) or normal (3000 ppm) diet of magnesium for 8 weeks. One half of each diet group received intramuscular injections of magnesium-depleting drugs, furosemide and gentamicin. The other half were controls and received equal intramuscular injections of saline. Auditory brainstem responses were obtained from all animals before and after 8 weeks of treatment of diet and drugs to examine the effects of treatment upon hearing and auditory brainstem function. A three-way analysis of variance of dietary magnesium, by drug and by sex, showed no significant differences in auditory brainstem wave V thresholds, wave V latencies, or interpeak wave I-V latencies between the control and experimental groups. The low magnesium diet group, which received drugs, had significantly greater wave V auditory brainstem response amplitudes. Results can be explained on the basis of magnesium influencing the uptake of calcium into both the hair cells and associated brainstem pathways.

Animals↗
PubMed1988

Use of adaptive digital signal processing to improve speech communication for normally hearing and hearing-impaired subjects.

A two microphone adaptive digital noise cancellation technique was used to improve word-recognition ability of normally hearing and hearing-impaired subjects in the presence of varying amounts of multitalker speech babble noise and speech spectrum noise. Signal-to-noise ratios varied from -8 dB to +12 dB in 4 dB increments. The adaptive noise cancellation technique resulted in reducing both the speech babble and speech spectrum noises 18 to 22 dB. This reduction in noise resulted in average improvements in word recognition, at the poorest signal-to-noise ratios, ranging from 37% to 50% for the normally hearing subjects and 27% to 40% for the hearing-impaired subjects. Improvements in word recognition in the presence of speech babble noise as a result of adaptive filtering were just as large or larger than improvements found in the presence of speech spectrum noise. The amount of improvement of word-recognition scores was most pronounced at the least favorable signal-to-noise ratios.

Adaptation, Psychological↗
PubMed1987

Application of adaptive digital signal processing to speech enhancement for the hearing impaired.

A major complaint of individuals with normal hearing and hearing impairments is a reduced ability to understand speech in a noisy environment. This paper describes the concept of adaptive noise cancelling for removing noise from corrupted speech signals. Application of adaptive digital signal processing has long been known and is described from a historical as well as technical perspective. The Widrow-Hoff LMS (least mean square) algorithm developed in 1959 forms the introduction to modern adaptive signal processing. This method uses a "primary" input which consists of the desired speech signal corrupted with noise and a second "reference" signal which is used to estimate the primary noise signal. By subtracting the adaptively filtered estimate of the noise, the desired speech signal is obtained. Recent developments in the field as they relate to noise cancellation are described. These developments include more computationally efficient algorithms as well as algorithms that exhibit improved learning performance. A second method for removing noise from speech, for use when no independent reference for the noise exists, is referred to as single channel noise suppression. Both adaptive and spectral subtraction techniques have been applied to this problem--often with the result of decreased speech intelligibility. Current techniques applied to this problem are described, including signal processing techniques that offer promise in the noise suppression application.

Acoustics↗
PubMed1987

Improvement in speech intelligibility in noise employing an adaptive filter with normal and hearing-impaired subjects.

It is well known that communication in noisy environments with reverberation present is a difficult problem to solve, particularly for the hearing-impaired listener. Two-microphone noise cancelling using an LMS adaptive filter in real time was used to process speech recorded in the presence of speech-spectrum noise at six different signal-to-noise ratios, -8, -4, 0, 4, 8, and 12 dB. Twelve normal-hearing and 11 sensorineural hearing-impaired subjects were tested. Results indicated mean improvement of 37.34 percent for the 12 normal-hearing subjects and 38.3 percent for 5 of the sensorineural hearing-impaired subjects. Individual data for the 5 remaining hearing-impaired subjects revealed severe speech intelligibility deficits when noise and reverberation contaminated the speech signal. It is proposed that rehabilitative audiological assessments include evaluation of an individual's ability to cope with reverberation and noise.

Acoustics↗
PubMed1981

The effects of alcohol on the acoustic Reflex Relaxation Index.

Normal-hearing young adults (6 M, 5 F) ingested 1.5 ml alcohol per Kg body weight over 90 min (blood alcohol level then being 0.104 +/- 0.016%), then tested for contralateral acoustic reflex (AR) threshold using an otoadmittance meter, and given the acoustic Reflex Relaxation Index (RRI) test of Norris, Stelmachowicz and Taylor. Each stimulus for the RRI was a 4-sec train of pulses at a level 10 db above AR threshold at .5, 1, or 2 kc/s, with equivalent on-time of 166.7 msec and off-time of 200 msec. AR responses were displayed on an X-Y recorder. RRI was taken as the percentage of total relation of the AR during off-times. The AR relaxed relatively more during off-times, and the RRI consequently significantly increased, in the alcohol vs the control condition, mean differences in RRI score in percent being 5.0, 12,9, and 21.3% for .5, 1, and 2 kc/s, respectively. Group mean RRI at all 3 frequencies under alcohol was close to the cut-off score suggested as "normal" by the test originators, but in 6 of the 11 Ss RRI interpretation by that criterion changed from "normal" to "not normal" under alcohol at one or more frequencies. There are unresolved differences in the effect of specific temporal stimulus patterning on RRI. Caution is recommended in interpreting RRI in the clinic as suggestive of sensorineural hearing impairment if S is at the time under the influence of a CNS depressant.

Adult↗
PubMed1978

Influence of alcohol on the acoustic reflex and temporary threshold shift.

Blood alcohol levels between 0.09% and 0.15% were found to reduce the protective action of the acoustic reflex in five human subjects with normal hearing. Specifically, acoustic reflex thresholds were raised, reflex magnitude decreased, and temporary threshold shift increased under alcohol conditions. Stimuli consisted of a narrowband noise (500 to 1,000 Hz) and a 500-Hz pure tone. Measurements were made at blood alcohol concentrations from 0.05% to 0.15%. Temporary threshold shift at 1,000 Hz was determined three minutes after a ten minute exposure of narrowband noise at -5, +5, and +20 dB relative to the subject's prealcohol acoustic reflex threshold.

Adult↗
PubMedDate not supplied

Effect of eye closure, mental concentration, and nonauditory sensory stimulation on the threshold and magnitude of the acoustic reflex.

Acoustic reflex threshold and magnitude were measured for normal-hearing subjects in four experiments under conditions of: (1) tight and relaxed eyelid closure; (2) eyes open and closed in light, focusing on a spot, reading, and solving a visual maze; (3) tactile stimulation; and (4) performing a mental task. Measurements were susceptance change in millimhos for a 220 Hz probe tone. A 1000 Hz pure-tone and broadband noise presented contralaterally were the stimuli. All factors affected reflex results. Eyelid closure enhanced reflex responses with tight closure involving voluntary muscle tension having a greater effect than relaxed closure. Both passive and active visual tasks suppressed the reflex. The mental task resulted in suppression of both reflex threshold and magnitude. Vibrotactile stimulation also resulted in a suppressed reflex. Changes were more pronounced with broadband noise as the reflex eliciting stimulus. Clinical implications are discussed.

Adult↗
PubMedDate not supplied

Alcohol and the acoustic reflex: effects of stimulus spectrum, subject variability, and sex.

Acoustic reflex thresholds were measured for eighteen young adults (9 men and 9 women) at four different blood alcohol levels: 0.00%, ascending 0.10%, 0.15% (peak level), and descending 0.10%. Reflex-eliciting stimuli consisted of three narrow-band noises (300 to 600, 600 to 1200, and 1200 to 2400 Hz) and three broad band noises (white noise, recorded rock music, and recorded factory noise). Prealcohol reflex thresholds were found to be significantly more sensitive than all postalcohol reflex thresholds for all stimuli, and broad-band stimuli demonstrated greater threshold shifts than did narrow-band stimuli. Significant sex differences were not observed for any blood alcohol level. Between subject variability was high, with 10 subjects showing little or no reflex threshold change and the other 8 subjects showing dramatic threshold changes.

Adult↗
PubMedDate not supplied

Effects of the visual modality on acoustic reflex magnitude.

Acoustic reflex magnitude for nine normal hearing subjects was measured with eyes opened and closed under three visual modality conditions: (1) in darkness; (2) in light without the ability to focus; and (3) in light with the ability to focus. Reflex magnitude decreased with eyes open for all three visual modality conditions; however, greater magnitude reduction occurred when the eyes were able to focus. Magnitude reduction for the three visual conditions was: 7% in darkness; 11% without visual focusing; and 20% with visual focusing. Additional data presented suggests reflex magnitude changes occur when eyes are held open with visual stimulation as a variable.

Accommodation, Ocular↗