Effects of total cochlear haircell loss on integrity of cochlear nucleus. A quantitative study

In cochleas of chincillas treated with amikacin, cochlear sensory cells were totally destroyed in all new-born animals. In animals treated as adults some occasional haircells remained in apical turns. In the neonatally treated animals, the resulting auditory deprivation significantly affected the volume of the ventral cochlear nucleus and large-dark spherical cell area. The density of large-dark spherical cells increased significantly from normal in both neonatally and adult treated groups. Our results suggest that the VCN is more dependent on auditory stimulation for proper development than the DCN. In adult chinchillas treated with amikacin there was a significant change in large-dark spherical cell density without a change in total cell numbers or large-dark spherical cell area volume. Our study indicates that the mature cochlear nucleus is much more resistant to the effects of auditory deprivation than the developing cochlear nucleus and that the maintenance of the mature auditory system is not as dependent on auditory stimulation. Studies such as this examining the morphological effects of profound cochlear deafness on higher levels of the auditory system are essential in cochlear implant research.

The effects of long and short term profound deafness on the responses of inferior colliculus to electrical stimulation of the cochlea

It is widely assumed that adequate sensory stimulation is important for the proper post-natal development of the central nervous system, particularly during certain critical or sensitive periods in development. To examine the functional effects of long-term profound deafness on the development of the auditory system, the response properties of neurons in the inferior colliculus (IC) to electrical stimulation of the cochlea were investigated in chinchillas (i) deaf from birth and (ii) deafened as adults. In animals deafened as adults there was a 50% reduction in the number of neurons activated by electrical stimulation of the cochlea, compared with studies in normal controls. In contrast, very few or no responses could be elicited from IC of animals made deaf from birth. The results imply that lack of neural activity in the ascending auditory pathways from an early stage of development results in an inactivation of IC neurons. It is not clear if such inactivity is temporary or permanent.

Morphological changes to the cochlea in an animal model of profound deafness

We have used systemic application of the ototoxic drug amikacin, to induce total cochlear haircell loss in the chinchilla, in order to create an animal model of profound deafness. We have produced models of both neonatal deafness (by treatment of new-born pups), as well as of acquired total hearing loss (by treatment of mature animals). We present a description of our techniques for producing cochlear lesions and for evoked potential monitoring of the resulting threshold elevations. We also give a qualitative description of cochlear haircell damage as viewed by scanning electron microscopy, and a quantitative assessment of the spiral ganglion cell survival after total haircell loss.

Acoustic analysis of voice in cochlear implant recipients with post-meningitic hearing loss

The objective of this study was to evaluate the critical time period between the onset of sensorineural hearing loss and cochlear implantation with respect to normal voice production in children with post-meningitic hearing loss. Acoustic measures of voice production were obtained from ten paediatric cochlear implant recipients with post-meningitic hearing loss. Acoustic measures were obtained utilising the Multi-Dimensional Voice Program and Computerized Speech Laboratory (Kay Elemetrics Corp.). Measures were based on sustained phonation of the vowel /a/. Acoustic parameters included fundamental frequency, short- and long-term frequency perturbation, and short- and long-term amplitude perturbation. Measures of fundamental frequency and short-term frequency and amplitude perturbation were comparable to values of children with normal hearing. Long-term control of frequency was within normal limits for subjects with a period of auditory deprivation of less than four months. Measures of long-term amplitude perturbation were normal for all patients except those with cochlear ossification. Early restoration of auditory feedback with cochlear implantation, the absence of cochlear ossification, residual aided hearing following meningitis, and auditory-verbal therapy were identified as factors in preserving the long-term control of frequency and amplitude in the setting of post-meningitic hearing loss.

Effects of chronic cochlear damage on threshold and frequency tuning of neurons in AI auditory cortex

We describe the effects of long-term cochlear lesions on the frequency response properties of AI cortical neurons in the cat. Young animals were treated with amikacin to produce bilateral, basal to mid-turn cochlear lesions. After 12-24 months the response properties of single neurons or small unit clusters in primary auditory cortex were recorded in anesthetized animals. Responses to stimulus frequency and intensity were mapped in detail and frequency threshold curves (FTCs) and Q10dB values were derived. Subsequent to recording experiments, scanning electron microscopy of the sensory epithelium was used to characterize the degree and extent of the cochlear damage. In normal control animals, Q10dB values were, on average, lower than those derived by others from cochlear nerve fibre recordings in the same species. In amikacin-treated animals, deterioration was evident in the threshold and tuning properties of cortical neurons, particularly in those cells whose input originated in damaged cochlear regions. Often, neurons associated with 'normal' cochlear areas (as assessed by scanning microscopy) also had poor frequency tuning compared with controls. As an animal model of sensorineural hearing loss, we consider the cat with long-term cochlear lesions to be more appropriate than animals with acute or short-term pathology. We also suggest that in making physiological-psychophysical correlations, neural responses from the central auditory system (e.g. cortex) should perhaps be given more consideration than data derived at the cochlear level.

The effects of crossed olivocochlear bundle section on transient evoked otoacoustic emissions

The purpose of this study was to investigate the effect of sectioning the crossed olivocochlear bundle (COCB) on transient evoked otoacoustic emissions (TEOAEs) in anesthetized adult chinchillas. Of particular interest is the role of cochlear efferents to the outer haircells (OHCs) and how they control mechanisms responsible for otoacoustic emissions. Specifically the experiment addressed whether a tonic level of inhibitory control is reduced by COCB section. The nonlinear component of TEOAEs was measured before and after COCB section. Analysis was made of the 1, 2, 3, 4, and 5 kHz frequency components and of the total emission, as quantified by fast Fourier transform (FFT) of the raw (time domain) response. After COCB section, the amplitude of the total response and of the 2, 3, 4, and 5 kHz components increased whereas the amplitude of the 1 kHz component decreased. The results indicate that COCB section reduces inhibitory control of the OHC mechanisms responsible for nonlinear TEOAE generation. It is not clear whether the nerve section eliminates a spontaneous level of activity in COCB efferents, or whether it results in the interruption of a stimulus-evoked feedback loop.

Neurone response latency in the inferior colliculus in relation to the auditory brainstem responses (ABR) in the guinea pig

In order to determine the possible source of the later vertex positive waves of the guinea pig auditory brainstem response (ABR), we have measured field potentials on the surface and at depths through inferior colliculus whilst making concurrent recordings of single unit responses (using identical broadband click stimuli). We find neurones, restricted to the antero-ventral inferior colliculus, with characteristic frequencies in excess of 12 kHz which have well synchronized onset responses short enough (c. 5 ms) to contribute to the P5 wave of the ABR.

Cytoarchitecture of cochlear nucleus in the chinchilla

The morphology of the cochlear nucleus in the normal, adult chinchilla, as demonstrated by Nissl staining, was examined. The cytoarchitecture was determined from sections viewed at the light microscope level. The chinchilla cochlear nucleus was found to possess most of the features reported in other mammalian cochlear nuclei. It could easily be divided into dorsal and ventral components due to an intervening layer of granule cells, and most cell types previously reported in mammals were also found in the chinchilla cochlear nucleus. A distinct distribution pattern of cell types exists within each part.

Some otological differences between pigmented and albino-type guinea pigs

Cochlear action potential thresholds across frequency (AP audiograms) and AP tuning curves were compared in albino (Dunkin-Hartley) guinea pigs and normal pigmented animals. AP audiograms were very similar; on average the albinos had AP thresholds 2-3 dB lower at 2 kHz and below compared with the pigmented guinea pig. AP tuning curves at 16 kHz were, on average, significantly less sharply tuned in the albino, but similar at 8, 4, and 2 kHz. Although we find only small differences in these measures of normal cochlear function, other evidence in the literature suggests that in auditory research the use of "albino" guinea pigs is best avoided.

An immunohistochemical and electron microscopic study of extra-renal basement membranes in dogs with Samoyed hereditary glomerulopathy

Samoyed hereditary glomerulopathy (SHG) in dogs has been employed as a model for human hereditary nephritis (HN), since affected dogs and patients show splitting of glomerular capillary basement membranes by electron microscopy (EM) and absent staining of glomerular capillaries for Goodpasture antigen (GPA) by immunofluorescence (IF). EM and IF were used to examine basement membranes (BM) in skin, lung, choroid plexus, lens, retina, and inner ear in SHG. By EM, BM in these tissues appeared similar in affected male, carrier female, and unaffected dogs. By IF, GPA could be detected only in lens capsule, internal limiting membrane of retina and basilar membrane of inner ear of unaffected and carrier female dogs, but not in affected male dogs. However, eye abnormalities and hearing loss were not present in any dogs, in contrast to their frequent occurrence in human HN. Our findings on extra-renal BM in SHG suggest that GPA is not required to maintain normal vision or hearing in affected male dogs and permit a greater understanding of the pathogenesis of human HN.

Psychometric properties of component and global measures of structured interview assessed type A behavior in a population sample

Structured interview (SI) assessments of global and component Type A behavior were conducted in a general population sample of 903 respondents. Correlations among all the measures were positive and significant. A factor analysis revealed that the common component variance was explained by a single underlying factor. Interrater reliabilities were approximately 0.5 to 0.7 for the individual components and 0.8 for both the SI global Type A and a second global measure that was assigned independently by assessors who did the component scoring. Prediction of the SI-assessed global measure from the components accounted for 56% of the variance, and prediction of the second global measure from the components accounted for about 83% of the variance. Implications of the psychometric properties of the SI component and global measures of Type A behavior for future research are discussed.

Developing criteria for ordering common ancillary services

This article describes the process utilized to develop criteria for appropriately ordering five ancillary services frequently performed in hospitals: 1) arterial blood gases, 2) electrocardiograms (ECGs), 3) serum electrolytes, 4) chest x-rays, and 5) complete blood counts (CBCs). The development of each set of criteria involved an initial consultant, a panel of six additional regional expert consultants, and three national reviewers. Each criteria set was developed through a process involving seven steps: 1) an initial working draft, 2) revisions at an initial meeting of the regional experts, 3) revisions at a second meeting of the regional experts, 4) written comments from the regional experts, 5) written comments from national reviewers, 6) additional written comments from regional experts, and 7) application of the criteria to cases in a community hospital. The change in item content was measured between steps and agreement with individual items was measured at steps 2, 3, and 4. The results indicate that appreciable change in content occurred with each step except step 4. Agreement started fairly high and was over 90% by step 4. The discussion considers the utility of each developmental step, factors affecting the utility of the criteria, the extent to which the results can be generalized, and the need for more research to identify optimal processes for the development of criteria to evaluate quality of care.

The use of a temporary extracochlear electrode in preoperative testing of permanent implant candidates

This paper describes hearing and speech perception in 9 post-lingually deaf adults fitted with a temporary single electrode, surgically positioned close to the round window niche. After baseline testing, unaided and aided binaurally with the high-power Phonic Ear PE 845, each subject was admitted to hospital for a period of 7 days. During each test session, stimuli were presented directly to the electrode lead by means of an isolation unit. Current thresholds, upper tolerable limits and gap detection were measured for various acoustical waveforms and stimulus frequencies. A laryngograph was used to test the discrimination of prelinguistic and suprasegmental speech features. The results indicated that the prosthesis could provide acoustic sensations of loudness, pitch and duration that changed with stimulus waveform, level of current and frequency, and a gap threshold less than 50 msec. Lipreading appeared to be a necessary adjunct for consonant discrimination.

A comparison of compound action potential and cochlear microphonic two-tone suppression in the guinea pig

Cochlear microphonics (CM) and compound action potentials (AP) were recorded simultaneously with differential electrodes in the basal turn of the guinea pig cochlea. When CM two-tone suppression (2TS) curves were compared to AP simultaneous masking curves, good correspondence was observed between CM and AP suppression effects. The relationship between the 10 dB bandwidths of CM and AP 2TS curves remained constant for each animal despite differences between animals resulting from natural variations. Under pathological conditions (acute cochlear hypoxia) both CM and AP two-tone suppression effects were greatly reduced or disappeared. These results can be taken as evidence that CM suppression and AP suppression are the products of a common underlying mechanism.

Psychosocial adjustment to and control of diabetes mellitus: differences by disease type and treatment

The relationship of diabetic patients' psychosocial adjustment to disease type, treatment mode, and indexes of control was examined in a representative community population. The psychometric properties of the Diabetes Educational Profile (DEP) and its application to psychosocial research in diabetes were also investigated. Findings support the reliability and validity of the DEP. Various measures of psychosocial adjustment were related to diabetes control but the specific relationships depended on the particular aspect of adjustment, the specific measure of diabetes control, and the type of disease and treatment. The findings suggest that analyses that aggregate dissimilar patient groups are subject to misinterpretation due to ecological masking and supressor effects. The results indicate that clinicians and researchers must recognize that patients with different disease types and treatment modes have different norms for psychological adjustment and diabetes control. Further, the particular aspects of psychosocial adjustment associated with diabetes control differ across patient groups.

Arterial blood supply to the auditory cortex of the chinchilla

Utilizing optical imaging we identified and named the arteries that supply the primary auditory cortex in the chinchilla (Chinchilla laniger). The primary auditory cortex is located 2-3 mm caudal to the medial cerebral artery and is supplied by it. Using corrosion casts and scanning electron microscopy we visualized the capillary networks in the auditory cortex and found regional variations in the densities of the capillary bed. We hypothesize that the uneven capillary densities observed in the auditory cortex correspond to neurologically more active areas.

Effects of glycerol on cochlear frequency selectivity in patients with Menière's disease

During transtympanic electrocochleography, action potential (AP) tuning curves were derived as a measure of cochlear frequency selectivity. In 18 out of 21 patients with symptoms of Menière's disease, a poor frequency selectivity was observed. In 12 subjects the effects on frequency selectivity of oral glycerol were measured, and in 5 patients AP tuning curves indicated an improvement in sharpness of tuning by a factor of 1.5-2.5. These changes started approximately 30 min after oral glycerol administration. In 2 subjects there was a deterioration in AP tuning. In 5 patients no significant changes were observed.

Motion sickness. Helping patients tolerate the ups and downs

The sensory conflict theory provides a useful framework for understanding motion sickness. Few modifications of this model have been proposed since its publication. The weak link in the study of motion sickness has been the failure to delineate the anatomic structures that correspond to the model's components. Effective pharmacotherapy is available for treatment of motion sickness. The choice should be based on the need to provide prophylaxis for or treatment of symptoms and on the side effect profile of the drug.

Total ablation of cochlear haircells by perilymphatic perfusion with water

Inner and outer haircells are destroyed within one day following perfusion of the perilymphatic spaces with water, otherwise the structural integrity of the cochlea and the organ of Corti are preserved. This technique is a reliable method to create an acute unilateral deafness model for investigations of auditory function.

Heart failure: clinical problem and management issues

Heart failure (HF) often presents as dyspnea either with exertion and/or recumbency. Patients also experience dependent swelling and fatigue. Measurement of the left ventricular ejection fraction (LVEF) identifies HF patients who may respond to pharmacologic therapy and/or electrophysiologic device implantation. Angiotension converting enzyme inhibitors, beta blockers, and aldosterone inhibitors can significantly lower the mortality and morbidity of HF in patients with an LVEF less than 35%. Cardiac defibrillators and biventricular pacemakers can also improve outcomes in selected patients with a decreased LVEF. The authors provide a guide for therapeutic decisions based on the inclusion criteria of the major clinical trials.

Development and validation of an A3 problem-solving assessment tool and self-instructional package for teachers of quality improvement in healthcare

PURPOSE

A3 problem solving is part of the Lean management approach to quality improvement (QI). However, few tools are available to assess A3 problem-solving skills. The authors sought to develop an assessment tool for problem-solving A3s with an accompanying self-instruction package and to test agreement in assessments made by individuals who teach A3 problem solving.

METHODS

After reviewing relevant literature, the authors developed an A3 assessment tool and self-instruction package over five improvement cycles. Lean experts and individuals from two institutions with QI proficiency and experience teaching QI provided iterative feedback on the materials. Tests of inter-rater agreement were conducted in cycles 3, 4 and 5. The final assessment tool was tested in a study involving 12 raters assessing 23 items on six A3s that were modified to enable testing a range of scores.

RESULTS

The intraclass correlation coefficient (ICC) for overall assessment of an A3 (rater's mean on 23 items per A3 compared across 12 raters and 6 A3s) was 0.89 (95% CI 0.75 to 0.98), indicating excellent reliability. For the 20 items with appreciable variation in scores across A3s, ICCs ranged from 0.41 to 0.97, indicating fair to excellent reliability. Raters from two institutions scored items similarly (mean ratings of 2.10 and 2.13, p=0.57). Physicians provided marginally higher ratings than QI professionals (mean ratings of 2.17 and 2.00, p=0.003). Raters averaged completing the self-instruction package in 1.5 hours, then rated six A3s in 2.0 hours.

CONCLUSION

This study provides evidence of the reliability of a tool to assess healthcare QI project proposals that use the A3 problem-solving approach. The tool also demonstrated evidence of measurement, content and construct validity. QI educators and practitioners can use the free online materials to assess learners' A3s, provide formative and summative feedback on QI project proposals and enhance their teaching.

Suppression by tones of the click evoked compound action potential in the normal and pathological guinea-pig cochlea and in man

The compound action potential (AP) to a broad-hand click stimulus, recorded from the round window in guinea-pigs and from the promotory in humans, was suppressed by a tonal stimulus. The degree of suppression depended upon the relative levels of the click and masking tones and upon the tone frequency. Using a fixed 50% suppression criterion, the tone-on-click masking revealed that for near threshold click levels a relatively narrow population of nerve fibres contributed to the AP. Both for threshold and suprathreshold clicks the population of neurones contributing to the AP was centred at the minimum of the AP audiogram with no shift toward higher frequency as the click level was raised. The shape of the response area revealed by tone-on-click masking is similar to that shown by tone-on-tone masking. Application of the tone-on-click masking technique to Kanamycin poisoned guinea-pigs and to humans with cochlear lesions indicated that useful information about residual hearing could be obtained even at very low frequencies.

Issues in the development, dissemination, and effect of an evidence-based guideline for managing sore throat in adults

BACKGROUND

In October 1995 the University of Michigan Healthcare System initiated a program to develop and implement guidelines for primary care in an effort to improve the quality and cost-effectiveness of care for common conditions associated with wide variations in clinical practice. One of these conditions was Group A beta-hemolytic streptococcus (GABHS), present in 5% to 20% of adults complaining of sore throat.

METHODS

A draft guideline was developed on the basis of a theoretical model of sore throat management, local data, and research evidence. The guideline was revised to reflect physicians' beliefs and practices regarding sore throat management. Guideline recommendations depended only on the number of clinical signs experienced by the patient and included testing only if it was likely to provide additional information about the probability of GABHS. Data on pre- and postdissemination data on patients presenting with sore throat were collected.

RESULTS

When physicians believed testing or antibiotics were unnecessary, only 7% of patients demanded screening and only 6% of patients wanted antibiotics. Physician beliefs about a patient's need for testing agreed with guideline recommendations in 63% of patients both before and after guideline dissemination.

DISCUSSION

Disseminating locally modified, evidence-based guidelines may not be sufficient to produce practice changes. If the guideline had been followed, the amount of testing would have been reduced by 17% and the appropriateness of testing improved for 32% of sore throat patients. The results indicate the need for implementation efforts that go beyond presenting evidence, even when that evidence is from both the literature and the local practice setting.

Improving HEDIS measurement: linking managed care organization and health system ambulatory care data

This article describes one health system's efforts to improve HEDIS measurement by integrating claims information from its managed care organization with data from its medical center's automated billing, scheduling, and clinical information systems. The authors discuss problems encountered while establishing an integrated measurement process and offer suggestions for others considering such an approach.

Loudness recruitment: contributing mechanisms as revealed by cochlear AP measures in man

A measure of the (average) rate of discharge versus intensity function of cochlear fibers can be obtained from cochlear-evoked compound action potentials using a tone-on-tone forward masking technique. The rationale for the method is presented. This technique was used to investigate, indirectly, cochlear fiber responses in human subjects, both with normal hearing and with deafness of cochlear origin and showing signs of loudness recruitment. In animals with pathologic cochleas, and change in rate of fiber discharge with intensity is more rapid than in normal animals. The present study confirms that this also is the case in human cochlear pathology and suggests that this abnormal steepening of rate versus intensity functions contributes to the phenomenon of loudness recruitment.