Biomedical subjects

J D Durrant

Publications and source records attributed to J D Durrant.

At least 19 recordsLinked to original sources

PubMed1999

Accuracy of hearing aid use time as reported by experienced hearing aid wearers.

OBJECTIVE: The purpose of this study was to investigate the relationship between the amount of time that a person reports wearing his or her hearing aid and the actual time that the hearing aid is worn. Although use time data are used in the analysis and interpretation of investigations concerned with auditory perceptual learning and with user satisfaction, the accuracy of self-reported use time has not been fully investigated. DESIGN: The experimental and control group were fit with a hearing aid that has the capability of storing use time data for later analysis. The experimental group was told that the self-reported use time would be verified with a computer analysis of the hearing aid that provides the actual use time. The control group was not informed of the use time validation procedure. The agreement between self-reported and actual use time was compared statistically between groups (knowledge of validation versus no knowledge of validation). RESULTS: The experimental group provided accurate self-reported use time whereas the control group showed a significant difference between actual use time and self-reported use time. CONCLUSIONS: The results may assist in the interpretation of results of previous investigations that have depended on self-reported use time and in the design of future investigations. For the clinician, the results indicate that relying on a patient's self-reported hearing aid use time for documentation of satisfaction or signal processing preference may be misleading.

Aged↗

PubMed1999

Somatosensory cuing of head-only rotational testing.

Head-only rotational testing (HORT) is a method of assessing the vestibulo-ocular reflex (VOR) that can be performed at the bedside with inexpensive, transportable equipment. Previous studies of HORT using auditory cuing have suggested that test results are in large part independent of the method by which a subject's head is moved, that is, active versus passive. However, many subjects have difficulty moving their head at rotational frequencies of 3 Hz or greater. In an attempt to overcome this difficulty, and to learn more about HORT, we explored the possibility of providing subjects with a somatosensory, rather than an auditory cue for head movement. Somatosensory, cues were provided either by applying gentle pressure against a tightly-fitted headband or by lightly tapping on the shoulders. Our results with young, healthy subjects indicate that somatosensory cuing is an efficacious means of inducing periodic head rotation and that HORT results are unaffected by the type of cue provided. We conclude that somatosensory rather than auditory cuing may be the preferred method of performing HORT.

Adult↗

PubMed1998

Are inner or outer hair cells the source of summating potentials recorded from the round window?

The relative contribution of inner hair cells (IHCs) and outer hair cells (OHCs) to the production of the summating potential (SP) is unresolved in the literature. Since OHCs in the base of the cochlea have been reported to produce little dc receptor potential except at very high sound pressure levels [I. J. Russell and P. M. Sellick, J. Physiol (London) 284, 261-290 (1983)], the IHCs appear to be the dominant source of the SP. However, results of intracochlear recordings are conflicting, although deriving from measurements in different turns of the cochlea [e.g., I. J. Russell and P. M. Sellick, J. Physiol. (London) 284, 261-290 (1983) versus P. Dallos and M. A. Cheatham, Sensory Transduction (1992)]. To determine which type of hair cells is the dominant source of the SP recorded at the round window, we used carboplatin to selectively destroy IHCs or a combination of IHCs and OHCs in the chinchilla. Related work, using measurements of distortion product otoacoustic emissions and cochlear potentials to assess the functional status of the OHCs served to validate this animal model [Trautwein et al., Hearing Res. 96(1-2), 71-82 (1996)]. The SP, cochlear microphonic (CM), and compound action potential (CAP) were recorded from the round window, and cochleograms were determined using well-established histological methods. The results were reasonably distinctive among three groups of ears--control (from untreated normal chinchillas), IHC-loss (extensive IHC loss with minor or no loss of OHCs), and IHC-OHC loss (total IHC loss plus extensive loss of OHCs over the basal half of the cochlea). Ears of chinchillas in the IHC loss group had a decrease of over 50% in SP output compared to control ears with the exact reduction depending somewhat upon the stimulus conditions. Ears in the IHC + OHC loss group, nevertheless, showed even further reduction in SP output which was clearly attributable to destruction of OHCs in the cochlear base. It was concluded that, although the IHCs are responsible for a greater contribution of dc-receptor potential to the SP recorded at the round window, a significant contribution is made by the OHCs, as well. The results suggest, specifically, that the round window "sees" SP output roughly in inverse proportion to the IHC:OHC. Lastly, the complexity of SP production, as recorded from the round window, precludes a completely straightforward interpretation of the SP:CAP in clinical ECochG.

Acoustic Stimulation↗

PubMed1998

Managing hearing loss in a patient with Alzheimer disease.

This case study reports the management of hearing loss in a patient with Alzheimer disease (AD) living at home with a spouse care giver. The report highlights the interaction between symptoms associated with AD and hearing loss and the lack of data regarding remediation of hearing loss in this population. Specifically, the case illustrates the modifications in evaluation and verification of the hearing aid fitting that may be advisable when working with patients with AD. The data for this patient illustrate some novel measurement techniques that may assist the professional in documenting the impact of treatment in this population.

Aged↗

PubMed1997

Evaluation of the nonorganic hearing loss suspect.

OBJECTIVE: To examine the utility of distortion-product otoacoustic emissions (DPOAEs) in the assessment of the nonorganic suspect because DPOAE analysis constitutes an objective test of hair-cell function that yields audiometriclike data. STUDY DESIGN: Retrospective study of clinical findings. SETTING: Audiology outpatient clinic of our university's medical center. PATIENTS: The study cohort comprised 30 patients who presented with a profile of suspicion for nonorganic hearing loss. Most cases were found, with the aid of DPOAE testing, to be nonorganic or to have nonorganic overlays to organic hearing loss. INTERVENTIONS: Interventions were diagnostic only. MAIN OUTCOME MEASURES: Observed audiometric findings and changes thereof. RESULTS: Statistically significant decreases in thresholds occurred in subgroups of those cases deemed to be truly nonorganic in origin. CONCLUSIONS: Especially considering test efficiency, the results support the inclusion of DPOAE analysis in the diagnostic management of the suspect-nonorganic patient.

Acoustic Stimulation↗

PubMed1996

Development of cochlear active mechanisms in humans differs between gender.

Despite onset of function early during the third term of gestation, the human auditory system demonstrates continued maturation, thought previously to occur primarily at the neural level. The electromotile properties of outer hair cells appear to contribute substantially to hearing sensitivity and frequency selectivity and lead to the generation of otoacoustic emissions (OAEs). This report demonstrates continued development of cochlear active mechanisms (i.e. end-organ level) after onset of cochlear function, as reflected by OAEs. Significant gender differences also are reported, corresponding to recently observed intersex differences in cochlear length and precursory to gender differences observed in the adult.

Cochlea↗

PubMed1996

Panic, agoraphobia, and vestibular dysfunction.

OBJECTIVE: Otoneurological abnormalities have been reported in panic disorder. The purpose of this investigation was to determine the prevalence of such findings in panic disorder with and without agoraphobia and to discern whether vestibular dysfunction was associated with specific symptoms. METHOD: Clinical audiological and vestibular tests were administered to 30 patients with uncomplicated panic disorder (without agoraphobia or with only mild agoraphobia), 29 patients with panic disorder with moderate to severe agoraphobia, 27 patients with anxiety but no history of panic attacks, 13 patients with depressive disorders but no history of anxiety or panic attacks, and 45 normal comparison subjects. Evaluators were blind to subjects' diagnostic group. Quantitative measures of subjects' discomfort with space and motion and of the frequency of certain symptoms between and during panic attacks were obtained. Anxiety state levels were measured during the vestibular tests. RESULTS: Vestibular abnormalities were common in all the groups but most prevalent in the patients with panic disorder with moderate to severe agoraphobia. Vestibular dysfunction was associated with space and motion discomfort and with frequency of vestibular symptoms between, but not during, panic attacks. There were no major differences between the two panic groups in anxiety levels during vestibular testing. There were no significant differences between groups on the audiological component of the test battery. Exploratory data analysis indicated that the constellation of vestibular tests most specific for agoraphobia was one indicating compensated peripheral vestibular dysfunction. CONCLUSIONS: Subclinical vestibular dysfunction, as identified by clinical tests, may contribute to the phenomenology of panic disorder, particularly to the development of agoraphobia in panic disorder patients.

Adult↗

PubMed1996

Localizing retrocochlear hearing loss.

PURPOSE: The origin of acute/sudden hearing loss is multifactorial. The association of vestibular symptoms does not necessarily isolate the pathologic condition to the inner ear. The audiogram provides a screen for differentiating conductive from sensorineural loss but often fails to provide more localizing information. METHODS: Three unusual patients with a variety of retrocochlear presentations of hearing loss are presented. Along with conventional auditory brainstem response (ABR) testing, newer auditory tests, including otoacoustic emissions and three-dimensional ABR analysis, can facilitate site-of-lesion testing. Magnetic resonance imaging (MRI) also provides graphic documentation for sources of retrocochlear hearing loss. RESULTS: One patient had gamma-knife treatment of an arteriovenous malformation, incurring a localised lesion to the inferior colliculus contralateral to the side of hearing loss. This effectively eliminated wave V, as confirmed by three-dimensional ABR analysis. A second patient with human immunodeficiency virus developed sudden complete hearing loss with retained otoacoustic emissions, confirming a retrocochlear lesion. A third patient with acute otitis media with sudden hearing loss and vertigo had an abnormal ABR and "mass lesion" on MRI. Hearing subsequently returned to normal, as did a repeated scan. CONCLUSIONS: The unique aspects of each case of retrocochlear hearing loss and the applied auditory electrophysiologic tests are reviewed.

Adult↗

PubMed1996

The efficacy of tympanic electrocochleography in the diagnosis of endolymphatic hydrops.

Electrocochleography (ECoG), an objective electrophysiologic test, is useful in the clinical diagnosis of endolymphatic hydrops. The purpose of this study was further to define the role of ECoG in the diagnosis of this disease. A retrospective chart review of 100 patients undergoing tympanic ECoG was undertaken comparing symptoms, degree of hearing loss, duration of disease, and diagnosis with ECoG results. The apparent sensitivity and specificity of ECoG in the diagnosis of endolymphatic hydrops were determined to be 57% and 94%, respectively. Three of 30 positive ECoG results were falsely positive. Fluctuating hearing loss and the degree of hearing loss (< 40 dB) and duration of disease (< 48 months) were statistically significant in predicting positive ECoG results. We conclude that a positive ECoG result is helpful in objectively confirming the disease. However, a negative result does not rule out hydrops.

Adult↗

PubMed1995

Middle ear effects secondary to nasogastric intubation.

A study was conducted of the status of the middle ear in neurologically impaired patients requiring extended nasogastric tube (NGT) feeding. Ninety percent of the study patients with NGTs demonstrated abnormal middle ear function via immittance testing; whereas, 8.5% and 0% of the clinical and normal control samples, respectively, had abnormal findings. These results support the need to conscientiously observe the middle ear status of patients requiring long-term NGT feedings. A plan for monitoring middle ear function in these patients is suggested.

Acoustic Impedance Tests↗

PubMed1994

3CLT ABR analyses in a human subject with unilateral extirpation of the inferior colliculus.

Reported are the results of analyses of three-channel Lissajous trajectories (3CLTs) of the auditory brain stem responses (ABRs) in a human subject in whom a focal lesion of the brain stem was caused by stereotactic radiosurgery, the 'gamma knife'. The surgery caused total destruction of the right inferior colliculus. The results, using multiple measures for defining ABR components, confirm findings from more conventional 2-channel recordings which, in turn, suggested the presence of an intact wave IV but a negligible, if not totally absent, wave V with stimulation of the left (contralateral) ear. The results thus support theories that wave V is generated by crossed pathways and that wave IV is an independent wave generated by the lateral lemniscus. Since magnetic resonance imaging suggested no destruction of tissue below the inferior colliculus, the findings also support theories of wave V generation at or rostral to the inferior colliculus. In practical terms, the results demonstrate the value of multichannel recordings of the ABR in component identification and in interpreting ABR abnormalities.

Adult↗

PubMed1994

Comparison of earphone radiation recorded from hearing impaired subjects and a resistor network simulator.

Electromagnetic radiation emitted by earphones is a potential source of contamination of auditory evoked potentials, particularly when long-duration stimuli are used to evoke the response. One practical solution to this problem would be to estimate the magnitude and characteristics of this earphone radiation so that an appropriate choice of earphone is made. With this aim, earphone radiation measures obtained from a resistor network simulator laid out over the dimensions of an average head were compared with those obtained from three hearing impaired subjects to determine the efficacy of the simulator in estimating the magnitude of this radiation. Results indicated a close agreement between these measures suggesting that the simulator measures are realistic. It was shown that the earphone radiation (i) increases linearly with stimulus intensity; (ii) varies systematically as a function of recording configuration; and (iii) recorded in the simulator can be used to subtract out earphone radiation contaminating evoked responses recorded from subjects using unshielded earphones. Based on these results it was concluded that the simulator provides a practical means to simulate real recordings, at least for the purposes of estimating stimulus artifact that may contaminate auditory evoked potentials to sustained stimuli.

Cochlea↗

PubMed1993

Observations on temporal aspects of bone-conduction clicks: real head measurements.

To further elucidate nuances of bone-conduction (BC) stimulation, particularly as they may pertain to BC-elicited auditory brainstem responses (ABRs), real head measurements were made of vibratory responses to BC clicks. A miniature accelerometer was held firmly against the skull near a bone vibrator applied to the mastoid, to the opposite mastoid, and to the forehead. Measurements also were made with the vibrator applied to the forehead and the accelerometer placed on a mastoid. The measured vibrations were compared among conditions within and across subjects. The results demonstrate that vibration picked up in the immediate vicinity of the vibrator, roughly mimics the temporal and spectral characteristics of the click observed on an artificial mastoid. However, probing at sites remote to the bone vibrator suggested the introduction of a propagation-like delay as well as low-pass filtering. These findings support observations of previous researchers who demonstrated phase differences between vibrations recorded at different points on the skull, further demonstrating the complexities of skull vibration. Latency differences of ABR responses obtained with forehead versus mastoid placements, for example, cannot be attributed merely to the difference in efficiency between sites of stimulation demonstrated audiometrically. While the real head observations do not permit determination of the actual vibratory lag at the cochlea, they do permit the deduction that a comparable onset delay occurs in BC as in air-conduction stimulation via supra-aural earphones.

Acoustic Stimulation↗

PubMed1992

Correlations of neuroanatomical measures to auditory brain stem response latencies.

Magnetic resonance imaging (MRI) was used to obtain measures presumed to scale the dimensions of the lower auditory pathway in humans for the purpose of further defining the relationship between length of the auditory pathway and auditory brain stem response (ABR) latencies. Specifically, measurements of soft tissue structures, that is, the eighth nerve and brain stem, were made for comparison with skull dimensions and ABR latencies. It was hypothesized that the brain stem dimensions covary significantly with skull dimensions and that the ABR parameters covary with both skull and brain stem dimensions. In general, only weak correlations were obtained with coefficients failing to reach statistical significance for most comparisons. These findings suggest that variance in ABR latencies cannot be attributed completely to variance in brain stem dimensions and raise suspicion that skull dimensions do not directly reflect brain stem dimensions.

Acoustic Impedance Tests↗

PubMed1992

The frequency-following response and the onset response: evaluation of frequency specificity using a forward-masking paradigm.

The onset and frequency-following response (FFR) components of the auditory brain stem response were investigated using a tone on tone forward-masking paradigm, as an alternate strategy to simultaneous masking, in an effort to further clarify the issue of place specificity of these components when elicited by a low-frequency stimulus (500 Hz tone burst). The results of this preliminary investigation suggest that both the onset and FFR components yield frequency-specific information, that is, they reflect activity along a limited apicalward region of the cochlea, but both are biased somewhat basalward to the place of the probe frequency. Also, of the two, the FFR is the relatively more place-specific response.

Acoustic Impedance Tests↗

PubMed1991

Analog model of human click-elicited SP and effects of high-pass filtering.

Recent advances in electrode design have helped to rekindle clinical interests in noninvasive electrocochleography--to enhance auditory brain stem response (ABR) recordings (namely, wave I) and to screen Meniere's disease. The salient feature of the response in suspected cases of endolymphatic hydrops is an unusually large summating potential (SP). Since the SP is a DC potential, conventional wisdom suggests the use of relatively low cutoff frequencies (i.e., long-time constants) for recording, but this may degrade the recording due to the presence of excessive low-frequency noise. However, the click-elicited SP also is a transient of relatively short duration, considering the characteristics of the click. This may permit more liberal high-pass filtering with acceptable wave-form distortion. This is a report of findings obtained using an analog model for SP generation and recordings from normal subjects using an electrode placed directly on the tympanic membrane. Responses were obtained using various low-frequency cutoffs. Cutoffs up to 30 Hz caused little distortion. Even in the face of considerable distortion at the highest cutoffs (100 and 300 Hz), the SP remained detectable and the SP:AP essentially unchanged. Therefore, higher filter settings may be used in recording the SP than commonly assumed, although the decreased amplitudes of the component potentials may not be tolerable under all clinical test conditions.

Adult↗

PubMed1991

On the origin of wave II of the auditory brain stem evoked response.

The generators of the several components of the auditory brain stem evoked response (ABR) have yet to be completely identified. However, there is compelling evidence to suggest specific generators for waves I and II, namely the distal and proximal portions of the auditory nerve, respectively. Although there is no question concerning the origin of wave I, there remains some uncertainty as to whether or not wave II arises entirely from the auditory nerve. The purpose of this study was to examine the behavior of wave II, as recorded via vertical versus horizontal derivations, in an effort to determine if wave II in both derivations is equally affected by stimulus manipulations (i.e., as would be presumed from a single generator theory). ABR recordings were obtained from normal-hearing young adults using vertical (hairline-to-ipsilateral mastoid and hairline-to-contralateral mastoid) and horizontal (mastoid-to-mastoid) derivations of responses to clicks presented at a variety of stimulus levels (40-80 dB nHL) and rates (19.9-59.9/sec.). The results indicate a shorter latency for wave II recorded in the horizontal derivation (wave IIa), compared to the vertical derivation (wave IIb). Also, wave IIa was found to be more susceptible to increased stimulus rate and exhibited a different latency behavior than wave IIb. These findings seem difficult to reconcile on the basis of a single generator for waves IIa and IIb.

Acoustic Stimulation↗

PubMed1991

Evaluation of three strategies for fitting hearing aids binaurally.

Three strategies for evaluating optimum frequency shaping and noise reduction in binaural digital hearing aids were compared in a repeated-measures design, using a new preference-based prescriptive fitting method. These strategies consisted of using preferred frequency shaping and noise reduction values binaurally: (1) based on monaural testing; (2) based on separate evaluations of each ear; and (3) based on evaluation of a second ear while subjects wore an aid programmed with the preferred values in the first ear. Individually preferred characteristics were programmed for 17 hearing-impaired subjects, most of whom exhibited symmetrical sensorineural hearing loss. Each subject was administered intelligibility estimation and midplane localization measurements in the laboratory, as well as a questionnaire survey based on situational listening in the real world. No statistically significant differences in preferences for either frequency shaping or noise reduction were found for the three fitting strategies, suggesting that monaural testing is sufficient in symmetrical cases to provide information for binaural fitting. Related to this finding, differences across binaural conditions were minimal for both intelligibility estimation and localization results. A significant improvement in localization performance under binaural conditions over monaural listening, however, was documented by both the laboratory and the real world data. A strong overall preference for binaural over monaural amplification was also documented under real world conditions.

Adult↗