Methodological problems in the determination of homolateral stapedius reflex threshold

Generally, a bilateral symmetry of the acoustic stapedius reflex is assumed. But a homolaterally higher sensitivity has been described. We examined 71 patients with complete unilateral deafness. With a TDH 39 headphone, stimuli of intensities up to 133 dB were conveyed to the deaf ear. A fairly accurate estimate of the normal homolateral threshold is obtained by correcting for the cross-hearing loss and by mathematical consideration of the relative probabilities of the positive and negative cases. Methodology-specific influences are discussed and a correction made for them. The homolateral reflex threshold is 9–14 dB lower than the contralateral reflex threshold.

Résumé

On suppose souvent qu'il existe une symétrie bilatérale du réflexe stapédien acoustique; cependant, une plus grande sensibilité homolatérale a été décrite par Møller et par Borg. Nous avons examiné 71 patients ayant une cophose unilatérale. Le stimulus (intensités allant jusqu'à 133 dB) fut donné à l'oreille sourde à l'aide d'un casque d'écoute TDH 39. Après avoir effectué une correction tenant compte de la perte dans l'audition croisée et des probabilités relatives des cas positifs et négatifs, nous avons pu déterminer avec une précision satisfaisante le seuil homolatéral du réflexe. Les influences méthodologiques spécifiques sont discutées et une correction est faite. Le seuil du réflexe homolatéral est plus bas (9–14 dB) que le seuil contralatéral.     

The effects of childhood otitis media on the acoustic reflex threshold at age 15

Previous research has found that childhood otitis media leads to elevated adulthood acoustic reflex thresholds because of worsened audiometric thresholds in the stimulation ear, and abnormality of the tympanic membrane in the ear from which acoustic reflexes were measured. To confirm and expand this finding, our research utilized longitudinal data from 631 general-population-sampled children assessed between ages 5 and 15. Otitis media was assessed to age 9, audiometric thresholds were measured at age 11, and otoscopy and acoustic reflex thresholds testing were performed at age 15. Our findings support the earlier research, in that acoustic reflex threshold was higher in those with the worst experience of childhood otitis media. However, this was directly mediated not by audiometric threshold in the ear to which the stimulus was delivered, but by the amount of tympanic membrane abnormality in both the stimulus and probe ears. This appeared to have an effect independent of audiometric threshold. Furthermore, only those who suffered the worst, persistent, binaural childhood otitis media showed raised acoustic reflex thresholds.     

Automatic Tympanometry in Clinical Practice

The probe tone of an impedance bridge has a direct effect on the results of tympanometry. The frequency of the probe tone should be close to the resonant frequency of the middle ear. Of three electro-acoustic bridges using three different probe tones, i.e. 800, 625 and 220 Hz, the one using 800 Hz provided the most indentifiable tympanographic pattern incases with ossicular discontinuity. Five different types of tympanograms could be indentified when an 800 Hz tone is used

The stapedius reflex thresholds, on the other hand, show only minor differences with different probe tone frequencies

Important clinical information can be obtained by combining the type of tympanogram with the results of stapedius reflex measurements     

Latency Measures of the Acoustic Reflex: Normal Versus Sensorineural

An ordered series of latency measures of the acoustic reflex was obtained on 23 normal-hearing and 23 sensorineural hearing-impaired subjects. Five parameters from each reflex recording were defined and measured. Statistical analysis revealed no difference between the two groups for the contraction or initial portion of the response. However, following the cessation of the stimulus, the sensorineural group demonstrated a significantly longer relaxation time     

Assessment of the efferent auditory system in children with suspected auditory processing disorder: the Middle ear muscle reflex and contralateral inhibition of OAEs

Objective: To determine whether children aged 7 to 12?years with listening difficulties show objective evidence for efferent auditory function based on measurements of medial olivo-cochlear and middle ear muscle reflexes.

Design: Click-evoked otoacoustic emissions recorded with and without contralateral broadband noise and ipsilateral and contralateral tonal (1000, 2000?Hz) middle ear muscle reflex thresholds were examined.

Study sample: 29 children diagnosed with suspected auditory processing disorder (APD) and a control group of 34 typically developing children participated in this study.

Results: Children with suspected APD had poorer performance on auditory processing tests than the control group. Middle ear muscle reflex thresholds were significantly higher at 2000?Hz in the suspected APD group for contralateral stimulation. MOC inhibition effects did not differ between APD and control groups.

Conclusions: This research supports earlier studies showing altered acoustic reflexes in children with APD. No group differences were found for the MOC reflex measures, consistent with some earlier studies in children with APD.     

A reappraisal of the salpingo-pharyngeus muscle

Summary Closure of the eustachian tube has been studied as a function of the salpingo-pharyngeus muscle. The muscle was dissected in ten cadavers and examined histologically. Its elastic fibres and anatomic relations especially during swallowing, together with other data, all confirm that the muscle is active at rest and relaxes during deglutition.     

The Role Of Electro-Physiological Tests in the Diagnosis of Non-Organic Hearing Loss

Today it is possible, by the use of newly developed tests, to diagnose cases of non-organic hearing loss with reasonable certainty. Having once decided that there may be non-organic elements, it is useful to supplement routine pure-tone and speech audiometry with a neurophysiological test like an ERA by means of which the auditory threshold can be established without the patients subjective judgement. A hearing loss which is apparent by routine pure-tone audiometry, but which is not evident after ERA is almost certainly non-organic, although confirmation of this state of affairs by other reliable tests is advisable. Measurement of the acoustic reflex thresholds and delayed speech feedback tests are both useful in this respect and rarely cause any confusion, except in some cases of true hearing loss in strongly recruiting ears.     

Influence of Tonic Reflex Activities on the Slow Auditory Evoked Potential

Possible influences of tonic reflex activities on the slow auditory evoked potential were investigated. For this purpose, the slow auditory evoked potential was picked up in 18 volunteers with normal hearing in relaxed position and in postures corresponding to reflex-induced positions and in 15 patients with cerebral palsy (CP) in tonic reflex pat-terns. No influence on latency for N₁₂₀ and P₂₁₅ due to postures could be observed' Latency within CP patients was age-dependent.

The effect of the reflex-inhibiting pattern (RIP) – the pattern inhibiting tonic reflex activity in CP patients as far as possible – on potential amplitude was different in the two groups. The effect of RIP in CP patients was comparable to the relaxed position in volunteers. This difference points toward an influence of tonic reflex activity on the slow auditory evoked potential.     

Single-unit characteristics in the auditory midbrain of the immobilized grassfrog

The anuran auditory midbrain of the grassfrog (Rana temporaria L.) was studied by a combined spectro-temporal analysis of sound preceding neural events. From the spectro-temporal sensitivities (STS) estimates of best frequencies (BF) and latencies (LT) were derived. Several types of STSs were observed: monomodal excitatory STSs comprised about half of the cases. Bimodal excitatory STSs, i.e. STSs with two discrete excitation regions, were observed in about 25%. Trimodal and broadly tuned STSs comprised about 5%. The remaining 20% of the STSs were characterized by inhibitory phenomena such as pure inhibition, sideband inhibition and post-activation inhibition. The distribution of best frequencies matches the frequency spectrum of the animal's vocalizations. A relative absence of monomodal units was noted in the mid frequency range. The distribution of latencies was bimodal over the range 7-108 ms. For each unit 6 functional parameters were determined; besides BF and LT these were: form of the STS (i.e. monomodality versus multimodality), spontaneous activity, binaural interaction, and firing mode (i.e. sustained versus transient) upon continuous noises stimulation. In addition, two structural parameters were considered: location in the torus and action potential waveform. Large correlations appeared between LT and action potential waveform, and between BF and binaural interaction type. Tonotopy was not found. A comparison was made between results from this study with a previous study on lightly anesthetized grassfrogs, using the same stimulus paradigms (D.J. Hermes et al. (1981): Hearing Res. 5, 147-178; D.J. Hermes et al. (1982): Hearing Res. 6, 103-126). Spontaneous activity, inhibitory phenomena and complex STSs were common using immobilization, whereas these have hardly been observed using anesthesia. Furthermore, interdependencies between the neural characteristics are substantially weaker for the immobilized preparation.     

Growth and spread of squamous cell carcinoma of the floor of the mouth

Summary Forty-eight specimens of carcinoma of the floor of the mouth were analyzed histologically by step serial sections. Five tumors were so-called superficial spreading carcinomas with large fields of cancerous mucosa, while 43 specimens showed advanced vertical growth into adjacent structures. Three different routes of invasion could be defined. The region of the sublingual gland was the main pathway in 23 cases. The space between the intrinsic muscles of the tongue and the genioglossus muscle was the main direction of infiltration for 14 tumors. Only 6 specimens showed direct invasion into the intrinsic tongue muscles. There was a good correlation between tumor thickness and the occurrence of metastases. Twenty-six patients (54%) showed metastases in regional lymph nodes and 13 patients with submandibular metastases already had developed metastases along the jugular vein. Unilateral or bilateral functional neck dissections remained the standard treatment procedure for all cases with depths of invasion over 5 mm. To avoid local tumor recurrences, patterns of invasion have to be considered. Soft tissue structures like the sublingual gland, intrinsic tongue muscles, genioglosssus muscle and geniohyoid muscle have to be resected routinely. Management of the mandible should be conservative if radiological and clinical investigations are negative. Correspondence to: H. Steinhart     

Choice of a tone-pip envelope for frequency-specific threshold evaluations by means of the middle-latency response: normally hearing subjects and slope of sensorineural hearing loss

The effects of stimulus rise-fall and plateau times on the middle-latency response (MLR) waveform (Na-Pa amplitude and Pa latency) were investigated in 14 normally hearing subjects and an objective MLR threshold was evaluated at low and middle frequencies in ten normally hearing subjects and ten patients with slope of sensorineural hearing loss, using a selected stimulus-envelope time. After analyzing the effects of envelope times on the MLR waveform and the spectra of tone-pips, it was found that a rise-fall time of 4 ms with a plateau of 2 ms (4–2–4) is an acceptable compromise between a synchronous discharge and frequency specificity for estimating the MLR threshold. The MLR threshold produced by 4–2–4 tone-pips approximated the psychoacoustic threshold at low and middle frequencies in the normal and hearing impaired subjects. This demonstrates the clinical usefulness of the MLR in estimating low- and middle-frequency thresholds.     

Audiological chronological findings in children with congenital anomalies of the central nervous system

Objective

To determine the frequency of hearing impairment in children with congenital anomalies of the central nervous system (CNS) by using detailed audiological evaluation methods.

Methods

The patients were 78 children with congenital anomalies of the CNS with a mean age of 29.5 months. They had been observed for a mean period of 38.5 months. Hearing levels were evaluated behavioral observation audiometry (BOA), visual reinforcement audiometry (VRA) and distortion product otoacoustic emissions (DPOAEs) were performed. Auditory brainstem responses (ABRs) and computed tomography (CT) scans of the temporal bone were performed in the cases in which the minimum response levels (MRLs) were above 30 dBHL. All cases were assessed in terms of developmental age.

Results

A total of 14.1% (11/78) of the children with congenital anomalies of the CNS were initially diagnosed with bilateral sensorineural hearing loss (SNHL). However, the hearing levels of nine of them improved by the time of the last diagnosis. Therefore, the patients with bilateral SNHL were only 2.6% (2/78) of the total patients with congenital anomalies of the CNS at last diagnoses. As shown by our results, many children with bilateral SNHL at initial diagnosis showed improved ABR thresholds and behavioral hearing thresholds with age. In this series, the use of hearing aids was arranged for six patients. However, four patients stopped using hearing aids when their hearing threshold levels improved. In two cases, there were no changes in hearing levels and the children continued using hearing aids.

Conclusion

Our results suggest that hearing level recovery can occur in some children with CNS anomalies. Confirmation of hearing loss in children with congenital anomalies of the CNS takes a long time. There are improvements in hearing loss during the observation period. Therefore periodic assessment of hearing is important.     

Oral microbiota and host innate immune response in bisphosphonate-related osteonecrosis of the jaw

Bacterial biofilms have emerged as potential critical triggers in the pathogenesis of bisphosphonate（BP）-related osteonecrosis of the jaw（ONJ） or BRONJ. BRONJ lesions have shown to be heavily colonized by oral bacteria, most of these difficult to cultivate and presents many clinical challenges. The purpose of this study was to characterize the bacterial diversity in BRONJ lesions and to determine host immune response. We examined tissue specimens from three cohorts（n530）; patients with periodontal disease without a history of BP therapy（Control, n510）, patients with periodontal disease having history of BP therapy but without ONJ（BP, n55） and patients with BRONJ（BRONJ, n515）. Denaturing gradient gel electrophoresis of polymerase chain reaction（PCR）-amplified 16 S r RNA gene fragments revealed less bacterial diversity in BRONJ than BP and Control cohorts. Sequence analysis detected six phyla with predominant affiliation to Firmicutes in BRONJ（71.6%）, BP（70.3%） and Control（59.1%）. Significant differences（P,0.05） in genera were observed, between Control/BP, Control/BRONJ and BP/BRONJ cohorts. Enzyme-linked immunosorbent assay（ELISA）results indicated that the levels of myeloperoxidase were significantly lower, whereas interleukin-6 and tumor necrosis factor-alpha levels were moderately elevated in BRONJ patients as compared to Controls. PCR array showed significant changes in BRONJ patients with downregulation of host genes, such as nucleotide-binding oligomerization domain containing protein 2, and cathepsin G, the key modulators for antibacterial response and upregulation of secretory leukocyte protease inhibitor, proteinase 3 and conserved helix–loop–helix ubiquitous kinase. The results suggest that colonization of unique bacterial communities coupled with deficient innate immune response is likely to impact the pathogenesis of ONJ.     

Diagnostic Significance of the Electrocochleogram in Clinical Audiometry

In order to understand fully the diagnostic significance of electorcochleography (E. Co. G.) in clinical audiology, the present study was designed to cover 3 problems concerning (1) objective threshold audiometry by E. Co. G., (2) objective bone-conduction audiometry by E. Co. G., and (3) objective differential audiometry of sensory-neural hearing loss by E. Co. G.

The compound action potential (AP) of the cochlear nerve was used as an indicator for this purpose. It was recorded simultaneously from both ears of the same subject with a promontory electrode or a meatal skin electrode by means of an average response computer.

Acoustic signals such as clicks or 3 different tone-pips with center frequencies of 2 000, 4 000, and 8 000 Hz, were given to the subject by both air-conduction and bone-conduction.

Five different electric indices were determined from the AP measurements as measures of neurophysiological activity of the cochlea, i. e., (1) the threshold of the AP, (2) the input-output function of N₁, (3) the increments of the N₁ amplitude, (4) the intensity-latency relation of N₁, and (5) the wave form of the AP. These results lead to the following conclusions

(1) The promontory-recorded AP thresholds were in an excellent agreement statistically not only with the subjective thresholds for the same stimuli but also with the clinical hearing thresholds shown on the audiogram.

(2) The promontory-recorded AP provided significantly more precise and reliable data on E. Co. G. as compared with the meatal skin surface-recorded AP. The difference between the AP thresholds and the subjective thresholds, on the average, was + 0.2 dB, subjective more sensitive, for the promontory recording, and + 17.8 dB, subjective more sensitive, for the meatal skin surface recording. But the choice of electrodes must be according to what is required of the E. Co. G.

(3) The bone-conduction AP measurements could be carried out with the promontory electrode. There was a relatively good agreement between the bone-conduction AP thresholds and the bone-conduction subjective thresholds, but the agreement was worse than that for the air-conduction AP measurements.

(4) An air-bone gap was determined objectively from the input-output and intensity-latency relations of the bone-conduction AP compared to those of the air-conduction AP. The promontory-recorded AP measurements by bone-conduction should be very helpful in estimating objectively the degree of an air-bone gap.

(5) There were some interesting correlations between the changes in the electric indices of the AP measurements and the patterns of subtractive loss. Some patterns of subtractive loss seemed to be specified by various combinations of the threshold elevation of the AP, the 'H curve' type of input-output relation, the reduction in the maximum amplitude of N₁, and the distortion of the AP wave form.

(6) A distinctive pattern of the distorted AP wave form appeared in Ménière's disease. The depression and recovery of the AP was closely correlated with the course of audiological and vestibular symptoms of this disease.

(7) On the basis of observations on the AP measurements for sensorineural hearing loss, 3 conceptual populations of sensory units are hypothesized, i.e., (a) the more sensitive population of sensory units capable of discharging well-synchronized impulses with lower thresholds, (b) the less sensitive population of sensory units capable of discharging well-synchronized impulses with higher thresholds, and (c) the more sensitive population of sensory units capable of discharging less well-synchronized or dispersed impulses with lower thresholds.

Finally, some serious problems confronting the routing clinical use of E. Co. G. are discussed, and the current status of E. Co. G. is described. It seems reasonable to speculate that E. Co. G., combined with electric response audiometry, will serve as the most practical method of objective differential audiometry as well as of objective threshold audiometry.     

Threshold of the Early Components of the Averaged Electroencephalic Response Determined with Tone Pips and Clicks During Drug-Induced Sleep

The early components of the averaged electroencephalic response (AER) were elicited from eight adults by narrow-spectrum tone pips centered at 250, 1 000, and 4 000 Hz, and by wide-band clicks. Brief naps were induced with secobarbital. Stimuli at 0, 10, 20, and 30 dB above behavioral threshold were presented in random order for each frequency. Control conditions in which no acoustic stimuli were presented were also employed. Responses were stored on magnetic tape and later scored independently on a yes-no basis by two judges who employed predetermined response criteria. Threshold for hearing (50-percent response) as measured with the early components was 20 dB sensation level (SL) for 250 Hz tone pips, and at 10 dB SL for 1 000 and 4 000 Hz tone pips and clicks. Thus, threshold estimated with the early components of the AER from sleeping adults closely approximated their behavioral threshold     

Long-term administration of magnesium after acoustic trauma caused by gunshot noise in guinea pigs

In a previous study we observed that a 7-day post-trauma magnesium treatment significantly reduced auditory threshold shifts measured 7 days after gunshot noise exposure. However this improvement was only temporary, suggesting that it could be potentially beneficial to prolong this treatment. The aim of the present study was to evaluate the efficacy of a long-term (1 month) magnesium treatment after an impulse noise trauma, in comparison with either a 7-day magnesium treatment, an administration of methylprednisolone (conventional treatment), or a placebo (NaCl). Guinea pigs were exposed to impulse noise (three blank gunshots, 170 dB SPL peak). They received one of the four treatments, 1 h after the noise exposure. Auditory function was explored by recording the auditory brainstem response (ABR) and measuring the distortion product otoacoustic emissions (DPOAE) over a 3-month recovery period after the gunshot exposure. The functional hearing study was supplemented by a histological analysis. The results showed that a 1-month treatment with magnesium was the most effective treatment in terms of hair cell preservation. The DPOAE confirmed this effectiveness. Methylprednisolone accelerated recovery but its final efficacy remained moderate. It is probable that magnesium acts on the later metabolic processes that occur after noise exposure. Multiple mechanisms could be involved: calcium antagonism, anti-ischaemic effect or NMDA channel blockage. Regardless of the specific mechanism, a 1-month treatment with magnesium clearly attenuates NIHL, and presents the advantage of being safe for use in humans.     

Practical model description of peripheral neural excitation in cochlear implant recipients: 3. ECAP during bursts and loudness as function of burst duration

In this, the third paper of the series, the loudness of low-rate bursts of electrical pulses was measured as a function of the burst duration, in subjects implanted with the Nucleus^® 24 cochlear implant system (three with straight and two with Contour™ electrode arrays). In order to help distinguish between the contributions of peripheral and more central effects, the ECAP was recorded to the individual pulses comprising the bursts, using the Neural Response Telemetry™ (NRT™) system. At a pulse rate of 250 pulses/s, the ECAP amplitude did not decrease greatly during the bursts: the mean reduction factor was 0.89. The time-constant for summation of the loudness contributions from the pulses comprising a burst was found to be larger than that associated with normal hearing. In addition, the first pulse of a pulse train was found to contribute much more to the overall loudness than did the subsequent pulses, although a corresponding difference was not observed in the ECAP recordings. These results establish a necessary connection between the essentially single-pulse model, developed in the fourth and fifth papers of the series, and the psychophysical data for pulse bursts, but they also have broader implications.     

Practical model description of peripheral neural excitation in cochlear implant recipients: 1. Growth of loudness and ECAP amplitude with current

This is the first in a series of five papers, presenting the development of a practical mathematical model that describes excitation of the auditory nerve by electrical stimulation from a cochlear implant. Here are presented methods and basic data for the subjects, who were implanted with the Nucleus^® 24 cochlear implant system (three with straight and three with Contour™ electrode arrays), required as background for all papers. The growth of subjective loudness with stimulus current was studied, for low-rate pulse bursts and for single pulses. The growth of the amplitude of the compound action potential (ECAP) was recorded using the Neural Response Telemetry™ (NRT™) system. An approximately linear relationship was demonstrated between ECAP amplitude and burst loudness, although this failed at the lower end of the dynamic range, to an extent that varied with subject and stimulated electrode. Single-pulse stimuli were audible below ECAP threshold, demonstrating that the audibility of burst stimuli at such low currents was not due solely to temporal loudness summation. An approximate function was established relating the curvature of the burst loudness growth function to the maximum comfortable level (MCL). Loudness at threshold was quantified, as a percentage of loudness at MCL. The relationship between loudness and ECAP growth functions, the curvature versus MCL function and the loudness associated with threshold are relevant to the development of a mathematical model of electrically evoked auditory nerve excitation.