Hearing threshold estimation by auditory steady state responses (ASSR) in children

Hearing threshold identification in very young children is always problematic and challenging. Electrophysiological testing such as auditory brainstem responses (ABR) is still considered the most reliable technique for defining the hearing threshold. However, over recent years there has been increasing evidence to support the role of auditory steady-state response (ASSR). Retrospective study. Forty-two children, age range 3-189 months, were evaluated for a total of 83 ears. All patients were affected by sensorineural hearing loss (thresholds ≥ 40 dB HL according to a click-ABR assessment). All patients underwent ABRs, ASSR and pure tone audiometry (PTA), with the latter performed according to the child’s mental and physical development. Subjects were divided into two groups: A and B. The latter performed all hearing investigations at the same time as they were older than subjects in group A, and it was then possible to achieve electrophysiological and PTA tests in close temporal sequence. There was no significant difference between the threshold levels identified at the frequencies tested (0.25, 0.5, 1, 2 and 4 kHz), by PTA, ABR and ASSR between the two groups (Mann Whitney U test, p < 0.05). Moreover, for group A, there was no significant difference between the ASSR and ABR thresholds when the children were very young and the PTA thresholds subsequently identified at a later stage. Our results show that ASSR can be considered an effective procedure and a reliable test, particularly when predicting hearing threshold in very young children at lower frequencies (including 0.5 kHz).

Are systemic oral steroids effective for sensorineural hearing loss in bullous myringitis? Considerations from a preliminary study

BACKGROUND

It is common in clinical practice to administer systemic steroids to treat sensorineural hearing loss due to bullous myringitis (BM). Nonetheless, there is currently no definitive evidence that steroid therapy is effective and appropriate for BM.

OBJECTIVE

The aim of this study was to assess the effectiveness of systemic steroid therapy for treating BM.

PATIENTS AND METHODS

This prospective study included 23 patients affected by BM with sensorineural hearing loss (median age, 45.8 years). The subjects were divided into two groups: Group A received only systemic antibiotic treatment and Group B received systemic antibiotics plus systemic steroid treatment.

RESULTS AND CONCLUSIONS

There were no differences between the groups in terms of the sensorineural hearing loss recovery. Both treatments were effective, suggesting that administration of oral steroids in combination with antibiotics did not confer an advantage in terms of sensorineural hearing loss recovery rate in the tested population.

Acute mastoiditis in children: the "Ferrara" experience

OBJECTIVE

This study aims to investigate the clinical features and outcomes of acute mastoiditis in children referred to the ENT/Audiology Department of the University of Ferrara from January 1994 to December 2005. It also aims to discuss risk factors and to find predictors for surgery.

METHODS

A retrospective study on case sheets of children with an acute mastoiditis diagnosis was carried out. Fifty-five cases fulfilled the inclusion criteria: they presented otoscopical evidence of acute otitis media and inflammatory findings of the mastoid area such as post-auricular swelling, redness or tenderness, protrusion of the auricle and/or radiological findings.

RESULTS

Twenty-six patients were only treated with antibiotic therapy, tympanocentesis alone was performed in 11 cases; in 5, a ventilation tube was positioned. Mastoidectomy was performed in 13 patients. The group who underwent mastoidectomy had a median hospital stay of 15 days (5-54), in this group were found the following complications: 1 meningitis, 1 meningo-encephalitis, 1 lateral and sigmoid sinus thrombosis, 1 facial palsy.

CONCLUSION

the incidence of otomastoiditis does not seem to be decreasing, on the contrary, in some countries, it seems to be on the increase. Our experience cannot confirm a real increase of the incidence but we noted periodic variations during the time of observation. It is important, that careful attention is paid to the clinical assessment of children who are 2-years old or under, as they seem to be more exposed to the risk of clinical complications; therefore, it is highly recommended that the otologist and the paediatrician collaborate closely.

Hearing in the elderly: a population study

An epidemiological study comparing speech audiometry with self-assessed hearing disability and an analysis of other factors influencing the quality of life was conducted. In the Veneto region (Italy), a representative sample of 2700 independently living individuals of 65 years of age and older was selected for the study. All participants were administered a comprehensive questionnaire and a brief examination at their home, including a general physical examination, speech audiometry, Sanders' Speech Disability test, part I and III, Mini Mental State Examination, CES-D scale for depression, visual acuity, self-reported diseases and physical function. Auditory function was worst in the older individuals: auditory performance was within acceptable limits up to the 75-79 age group, while it rapidly deteriorates in the older groups. This trend is consistent with self-reported auditory disability (Sanders' test). A detailed analysis of the type of errors made in the speech audiometry was conducted for each subject. Speech audiometry is a good indicator of real hearing difficulties faced by the elderly, and it might be preferred to pure-tone audiometry, since hearing deficits with age are not always limited to an increased detection threshold, but include other aspects of hearing such as distortion of sounds, comprehension of speech and noise discrimination.

Cisplatin ototoxicity in the Sprague Dawley rat evaluated by distortion product otoacoustic emissions

The present study has evaluated the use of distortion product otoacoustic emission (DPOAE) responses in the detection of cisplatin-induced ototoxicity in a Sprague Dawley rat animal model. The cisplatin was administered as a 16 mg/kg, dose introduced by a slow 30-min intraperitoneal infusion. Data from three DP-gram protocols, DPOAE input-output responses at 8 kHz, and auditory brainstem responses (ABRs) at 8, 12 and 16 kHz were collected before and 72 h after treatment. The post-treatment ABRs at 16 kHz showed the greatest mean threshold shift of 33.6 dB. The post-treatment DP-gram data showed significant reduction of the signal to noise ratios in the majority of the frequencies tested, across all tested protocols. The data suggest that the most sensitive DPOAE procedure for the early detection of the cisplatin-induced ototoxic damage is the DPOAE I/O protocol. Morphological analyses indicated that the inner hair cells remained intact, while several types of alterations were observed in the arrangement of the stereocilia in the outer hair cells.

[Loudness scaling for narrow band noise and speech signal]

A group of normal-hearing subjects underwent an experimental procedure to obtain estimates of loudness for two narrow band noises, centered at 0.25 and 3 kHz respectively, and meaningful unfiltered speech signals (sentences). Stimuli consisted of 12 intensity levels, spaced equally over the dynamic auditory range. The subjects were asked to associate each level of intensity to one 7 loudness categories. The loudness growth for a noise bands is defined by an exponential function. The loudness growth for the speech signal is better approximated by a linear function. However the mean intensity/loudness function shows two steep portions at the low and high intensities and these are separated by a shallow tract between 55 and 75 dB SPL. The loudness growth for meaningful speech signals--differing from the typical exponential function shown by noise stimuli--seems to confirm the contribution of factors that depend on central auditory organization, most likely operated by the perceptive auditory continuity attributes and the semantic content of the speech signals.

Clinical applicability of transient evoked otoacoustic emissions: identification and classification of hearing loss

The study aimed at the development of a clinically applicable methodology that could: (1) discriminate transient evoked otoacoustic emission (TEOAE) recordings from normal hearing or hearing impaired individuals; (2) classify the nature of the hearing loss as conductive or as cochlear, and (3) define clear-cut TEOAE clinical criteria. A classification algorithm based on a multivariate discriminant analysis of fast Fourier transform data from recordings evoked by click stimuli of 50 +/- 2, 62 +/- 2, 68 +/- 2 and 80 +/- 2 dB SPL was used to discriminate 302 normal subjects from 383 subjects suffering from mild to moderate hearing losses. The best discriminant model (QDF80) produced a sensitivity of 93.8% and a specificity of 79.4%. When extra correlation criteria were serially applied to the classification outcome, the specificity was increased to 85.3%, but the sensitivity was marginally decreased to 91.7%. The classification of the correctly identified hearing-impaired cases yielded 93.8% identification of conductive and 75.1% identification of cochlear cases. A sensitivity analysis of the misclassified hearing-impaired cases suggested that the TEOAE spectra are well correlated with the 2-kHz but poorly correlated with the 4-kHz octave frequency.

Audiometric patterns of genetic non-syndromal sensorineural hearing loss

Sixty-five families with non-syndromal sensorineural hearing loss (NS-SNHL) of genetic aetiology were subtyped according to Gorlin et al. Individual audiogram shapes were also classified in order to detect inter- and intra-familial variations. In 48 families with an Autosomal Dominant (AD) inherited form, 26 exhibited the features of (high-frequency) progressive NS-SNHL, 12 those of mid-frequency NS-SNHL, 5 were affected by congenital low-frequency NS-SNHL; 1 kindred showed a progressive low-frequency pattern and another 1 a unilateral NS-SNHL; only 3 kindreds were affected by severe congenital NS-SNHL. Autosomal Recessive (AR) inherited forms were composed of 9 kindreds with severe congenital NS-SNHL, and 7 with moderate congenital NS-SNHL. One X-linked form was identified. AD- and AR-inherited NS-SNHL differed significantly both in severity of hearing impairment and in audiogram shapes. With few exceptions, in each family classified according to Gorlin, most of the affected subjects shared the same audiogram profile. Intrinsic progression of the disease versus ageing was studied in the larger subtype of individuals with the high-frequency loss. Gorlin's classification still remains the best system to classify NS-SNHL, and can provide a broad base to separate a very heterogeneous group of disorders. Results obtained in gene mapping in single large human families or in homologous gene search could be tested in our families. For some of them, namely those with high frequency progressive and low-frequency NS-SNHL, testing should already be feasible.

[Influence of a CNS pathology on the electrocochleography response]

This study analyzed 73 electrocochleographic recordings made in children with a normal hearing threshold, selected retrospectively from 1563 recordings made between 1973 and 1990. The aim of the study was to check the original findings for any correlation between the various response parameters which might be indicative of a pathological condition. Compound action potential (AP) latency and amplitude, presynaptic summation potential (SP) and cochlear microphonic (CM) amplitudes and AP rapid adaptation behavior were calculated and recordings were associated with clinical information on aetiologic diagnosis, otoscopic examination, impedance measurement data and the finding of any central nervous system (CNS) pathology. The trend of the amplitudes as a function of the intensity of all three potentials (input-output functions), CM and SP in particular, demonstrated unexpected scattered values especially towards the high intensities. This was found correlated to the presence of CNS pathology. The comparison between the two groups (with vs without CNS pathology) with the aid of the Student's t-test proved statically significant, especially for CM and SP amplitudes while rather less so for AP amplitude. In particular, all CM and SP amplitude values outside the confidence intervals (calculated as 95% of normal cases) revealed CNS pathology. It has been suggested that the influence of the CNS on cochlear function is due to a disturbed function of the olicocochlear bundle, which is known to have an inhibitory effect on cochlear dynamics; furthermore, there is also proof that it can be activated regardless of any ipso-and/or contra-lateral acoustic stimulation. The effects observed on the electrocochleography in cases with CNS disorders would thus be explained by an interruption of the olivocochlear bundle at the CNS level or a disruption of the CNS mechanism capable of controlling its activation.

[Hemangiopericytoma of parapharyngeal space]

The parapharyngeal space is a rare site of parapharyngeal neoplasms: their diagnosis and therapeutic treatment offer peculiar challenges. Parapharyngeal tumours may be primary, metastatic or diffused with regaed continuity. They are mostly benign (mixed, neurogenic, vascular tumours, etc.) rather than malignant neoplasms (adenocystic carcinoma, adenocarcinoma, lymphoma, etc.). In order to diagnosis parapharyngeal tumours differentially it is important to consider very rare type of neoplasms such as hemangiopericytomas. In this paper the Authors describe a case of hemangiopericytoma of the parapharyngeal space indicating the main diagnosis procedures, especially CT scan, Magnetic resonance and angiography. They discuss pathological aspects with particular regard to the differential diagnosis between benign and malignant tumour of this kind as well as prognoses. The Authors also describe surgical treatment in relation to particular parapharyngeal localization.

Ultrastructural analysis of the chorda tympani nerve in facial paralysis from different etiologies

Twelve chorda tympani segments, removed from as many patients (7 females, 5 males) affected by otosclerosis (3, as controls) and from either idiopathic (4), or traumatic (3) or herpetic (2) facial paralysis, were examined by a transmission electron microscope, in order to verify chordal ultrastructural changes, the gravity of neural damage in the various types of facial paralysis and the role played by chorda tympani on the etiopathogenesis of the idiopathic form. The segments were obtained, while performing a stapedectomy in otosclerotic patients and, in facial palsy, while performing chordal neurotomy or direct decompression of the II and III portio of the VII nerve. The obtained data showed no noteworthy alterations concerning myelinated and unmyelinated nerve fibers and chordae stroma in otosclerotic patients, confirming their reliability as controls. In facial paralysis, both normal ultrastructures and alterations were noticed, even though polymorphic: unravelling and dissociation of the lamellae sheaths up to a point of degeneration with a more or less complete resorption of myelin, accumulation of dense bodies and electron-dense formation, particularly in unmyelinated fibers, vacuoles in myelinated fibers, intracytoplasmic vacuoles in Schwann cells and, in herpetic forms, an occasional presence of inflammatory cells. Such results demonstrate that, in any type of facial paralysis, the ultrastructure of the chorda tympani is constantly involved, probably due to main trunk involvement. In the idiopathic forms the alterations of the chorda look like to degenerative alterations caused by traumato-ischemic events, rather than to cytopathic lesions induced by herpetic virus.(ABSTRACT TRUNCATED AT 250 WORDS)

[Invasive nasosinusal aspergillosis in an immunocompetent patient]

The authors describe a case of invasive nasosinusal aspergillosis in an immunocompetent patient. After a careful bibliographic review, they emphasize that in the present case the diagnosis was made by means of fungal culture as the clinical picture, imaging techniques and histopathological findings were aspecific. The pathogenetic agent resulted Aspergillus tamarii which belongs to the Aspergillus flavus group and is one of the most unusual agents in literature. The treatment of choice, in the invasive form, is surgery that should be as radical as possible followed by a medical therapy. In the present case, after two-phase radical surgery on all the paranasal sinuses, medical treatment with traconazole was employed with excellent local results at a follow-up of one year.

Observations on the ABR I-V interval in a clinical sample of elderly patients

ABR I-V interval in elderly patients, analysed by multiple regression analysis, was found to be dependent on hearing threshold slope and sex, while the contribution of age and hearing loss was not significant. Since these results partly disagree with other reports which demonstrate that I-V interval is significantly related to age and hearing threshold, caution is suggested in inferring general conclusions on age effects, if data are drawn from clinical samples.

Plexiform neurofibroma of the cervical portion of the vagus nerve

The authors describe a rare case of plexiform neurofibroma of the cervical portion of the vagus nerve, and discuss its aetiopathogenesis, clinical, histological and therapeutic features, emphasizing the difference from other benign tumours of the vagus nerve. The clinical characteristics of the mass, ultrasound tomography, CT scanning and digital subtraction angiography were useful in defining its extension and relationships with the surrounding structures. Surgery is the treatment of choice. After mentioning the most commonly employed surgical approaches, they emphasize the advantages of the lateral-cervical approach which allows a wide exposure of the possible sites of origin of the tumour and its complete removal. Finally they stress the need of an accurate histological and immunohistochemical examination in order to differentiate neurofibromas from neurilemmomas.

Cochlear and neural dysfunction in acoustic neuroma: can they be separately revealed by auditory brain-stem wave V latency?

Cochlear and retrocochlear lesions may be differentiated by a diagnostic index (D5), which is derived from the patient's auditory brain-stem wave V latency and pure-tone hearing threshold at 2 to 4 kHz. The D5 values obtained from 49 cases of acoustic neuroma (AN) have been shown to share some properties with D5 values of patients with cochlear hearing loss (280 cases), indicating a lesser prolongation of wave V latency in cases with pronounced hearing loss. Assuming this finding is indicative of some degree of cochlear impairment concomitant to the neural dysfunction, AN data were corrected in an attempt to remove the effects of cochlear impairment. The resulting D5 values could reflect the delay in wave V solely due to the neural dysfunction. A significant relationship between these D5 values and tumour size seems to support this hypothesis.

[Considerations on analysis time duration in a posturographic study in normal subjects]

In order to evaluate the importance of analysis time on posturographic parameters (average X, Y and R, Sway Path, Sway Area, Ellipse Area) both with eyes open and closed, 24 normal subjects were examined for an overall period of 60 seconds. Mean +/- 1 SD values of each parameter were obtained for each time interval (0-20, 20-40, 40-60 sec.) into which the overall period was divided. With the eyes open, the parameters for each time interval did not differ significantly and they were always lower than those obtained with the eyes closed. On the other hand, with the eyes closed, there was a significant reduction in the various parameters as analysis time progressed. In 4 out of 24 subjects an inverse behaviour was detected. The authors conclude that the open-eye analysis time could be limited to 20 sec while, due to changes observed in the various posturographic parameters, closed-eye analysis time should be extended to 60 seconds. The analysis time may prove important in identifying peripheral or central vestibular pathologies since it may be that some of them induce earlier alterations of posturographic parameters while in other pathologies such changes are observed later on.

[Our experience with mandibular fractures]

The authors relate on their own experience concerning etiology, diagnosis and treatment of mandibular fractures. 320 patients (252 males and 68 females) aged between 6 and 82 years with posttraumatic fractures of the mandible, 188 with a single and 132 with multiple fractures, underwent surgical and/or orthopedic treatment. Interosseous wiring and seldom application of metallic plates were the preferred techniques when surgery was performed. Intermaxillary fixation was carried out when the orthopedic treatment was needed. Often both methods were associated. In 10% of the condylar fractures the condyle has been removed. Functional results were excellent and no serious complications could be observed. In 11% of the cases with condylar fractures some limitation of the mandibular movements could be observed, while when condyles were not involved malocclusion could be observed in 3% of the cases. The authors discuss upon etiology, by comparing their own with other experiences, upon diagnosis, which does not seem difficult if adequate radiological investigations are carried out; finally they relate briefly on the advantages and disadvantages of the different surgical and non surgical techniques. Based on their experience they conclude that interosseous wiring and, in selected cases, the application of metallic plates, using an external approach, mostly associated with intermaxillary fixation, represent a safe and adequate treatment for almost every fracture of the mandible.

40-Hz steady-state responses in newborns and in children

The authors investigated the 40-Hz steady-state responses (SSR) in 32 full-term newborns and in 10 normal children (5-8 years old), using 500-Hz tone bursts. The 40-Hz SSR threshold is located at about 50 and 30 dB nHL in newborns and older children, respectively. The latencies of both P1 and N1 waves decreased significantly with age, while the amplitudes increased. No significant latency and amplitude intersex differences have been observed. Moreover, with age, the 40-Hz SSR became more stable, their test-retest replicability improved, and P1-N1 wave occurrence increased. The authors finally discuss the possible underlying mechanisms of these findings and conclude that the 40-Hz SSR are difficult to obtain and are scarcely reliable in defining the low-frequency threshold in newborns. The stability and reliability of the responses increase with age, and the electrophysiological and behavioral thresholds to low-frequency stimuli tend to overlap.

[Influence of static stimulation of cervical and otolithic receptors on posturographic parameters]

In the present work 30 normal adult subjects (20 males, 10 females; age range 25-40 years) having no signs or symptoms of vestibular involvement were studied in order to verify whether posturographic parameters could be influenced by the static stimulation of cervical and otolithic receptors. The posturographic evaluation was carried out using a stabilometric platform (Bertec) with the subject standing and the head in one of the following positions: median position, turned left (45 degrees), turned right (45 degrees), tilted left (40 degrees), tilted right (40 degrees), with eyes both opened and closed. The data obtained indicate that wide standard deviations exist in the observed parameters and no significant changes were observed with the head turned either to the right or left nor with the head tilted in either direction. Moreover, the posturographic data obtained with eyes open were slightly reduced in comparison to those obtained with the eyes closed. One can, thus, conclude that neither cervical nor otolithic inputs influence posturographic parameters under static conditions, while visual inputs modify significantly posturographic data, except the coordinates of the foot center of pressure.

[Ultrastructural aspects of cholesteatoma of the middle ear]

Middle ear cholesteatomas were intraoperatively obtained from 6 male patients and studied under light (L.M.), transmission (T.E.M.) and scanning (S.E.M.) electron microscopy. Cholesteatoma proved to be formed by keratinizing squamous epithelium, or matrix, and by connective tissue, chorion or perimatrix. With regard to the matrix, a progressive differentiation of cells belonging to the stratum germinativum could be observed towards spinosum, granulosum and corneum cells with formation of keratinized lamellae. Moreover, keratinocytes and Langerhans cells were found in the stratum spinosum. The perimatrix consisted of granulation tissue, or inflamed subepithelial connective tissue displaying inflammatory cells. Furthermore, the advancing front of cholesteatoma proved to be formed by lymphocytes and plasma cells, partially covered by respiratory type epithelium.

[Quantitative abnormalities in nystagmus induced by caloric stimulation in multiple sclerosis]

Vestibular nystagmus induced by caloric stimulation (20 degrees and 44 degrees C) was evaluated in terms of duration, frequency and slow phase velocity in 80 patients suffering from clinically defined multiple sclerosis. Criteria of abnormality were established with reference to 3 confidence levels from normative data of a 15-subject control group. Abnormal data representative of vestibular hypo- and hyperreflexia were found ranging between 27 and 53% depending on different parameters and diagnostic criteria. Significant differences in occurrence of nystagmus abnormalities became evident by analyzing 6 different windows of the vestibular response. Different distributions of hypo- and hyperreflexia were observed in relation to the time-course of the normal cumulative response curve, as well as to different stimulus temperatures. For each subject the abnormal data of the 2 stimulated ears X 2 caloric stimulations X 6 analysis windows were cumulated, yielding an overall outcome of pathological results in 66% to 90% of the patients, depending on the different diagnostic criteria.

Radioisotopic method for nasal mucociliary function evaluation

In 13 healthy young adults, nasal mucociliary transport velocity was measured by means of albumine microsphere labeled with Tc99m as a tracer. M + ISD of clearance velocity values and of the half time radioactivity (T1/2) resulted to be respectively 1.02 + 0.22 cm/min and 1.07 + 0.24 min. A significant correlation (P less than 0.05) between half time clearance (T1/2) values of the radioactive particles and the mucociliary velocity ones could be detected, making T1/2 a reliable and rapidly obtainable parameter for determining nasal mucociliary function. Advantages and disadvantages of the different techniques are discussed.

The behaviour of wave V latency in cochlear hearing loss

The audiological approach to the early diagnosis of cerebellopontine angle tumours (APC) is based mainly on ABR. In present work, wave V latency has been studied in two groups of patients: 308 cochlear cases and 74 retrocochlear cases (APC surgically confirmed tumours), in order to increase the sensitivity and specificity of the diagnostic indexes I-V, IT5 and Delta V. Wave V latencies have been evaluated in relation to hearing loss at 2-4 kHz and audiometric profile. Both these factors show a highly significant positive correlation with the latency, which consequently increases proportionally to hearing loss and high-frequency audiometric loss. A multiple regression analysis was therefore used to analyse the effects from the two variables, and a correction factor was calculated to compensate the latency values for hearing loss and threshold configuration. The effects of such a correction on the clinical results consist mainly of a reduction in the rate of cochlear false-negative results, which corresponds to improving the ABR specificity.

Microbial flora of surface versus core tonsillar cultures in recurrent tonsillitis in children

Surface and 'core' tonsillar specimens were collected from 60 children, between 2 and 14 years of age, suffering from recurrent tonsillitis, in order to establish the reliability of surface tonsillar swabbing technique and to define the most frequently involved aerobic and anaerobic microorganisms. From the qualitative point of view, the same mixed aerobic and anaerobic flora were obtained in both samples thus demonstrating the reliability of the surface swabbing technique. From the quantitative point of view, 187 microorganisms, 129 (69.2%) aerobes and 58 (30.8%) anaerobes were isolated from surface cultures while 184, 109 (59.2%) aerobes and 75 (40.8%) anaerobes from the core cultures, thus demonstrating a greater number of anaerobes in the core of the tonsil. The most common isolated aerobic microorganisms were the alpha- and beta-hemolytic Streptococci, the Neisseriae and the Staphylococcus aureus; the predominant anaerobic ones were the Fusobacterium nucleatum, the Bacteroides sp. and the Veillonella parvula. The isolated staphylococcus aureus and the bacteroides sp. were all beta-lactamase producers.

40-Hz auditory event-related potential in normal adults

40-Hz event-related potentials (AERP) in response to 0.5-, 1-, 2- and 4-kHz tone pips were studied in 45 subjects (18 males and 27 females) in order to assess their reliability and threshold in normal adults and to study the effects of stimulus frequency and intensity on their latency and amplitude. In all subjects well-formed and reproducible 40-Hz AERP were detected, thus showing a good reliability of 40-Hz AERP to tone pips. The response was always detectable within 15 dB nHL intensity level and showed a sequence of positive (P1, P2 and P3) and negative (N1, N2 and N3) waves. It has also been observed that the latency of the first component following the acoustic stimulus decreased at increasing stimulus frequency and intensity, while the amplitude of the whole response increased upon increasing stimulus intensity. It can be suggested that the 40-Hz AERP to tone pips may represent a useful tool in assessing auditory threshold in the low-frequency range.

Auditory brainstem responses in noise-induced permanent hearing loss

Fifty-four patients (108 ears) with presumed noise-induced hearing loss, were subjected to tonal and speech audiometry, impedance tests and measurements of auditory brainstem responses (ABR), in order to check for possible retrocochlear involvement. ABR data indicated that latency values of waves I, III and V, as well as III-I, V-III and V-I intervals fell within the normal range in all cases (M +/- 2 SD), even for fast repetition rates (51 stim/s). Poor waveform resolution of early components, particularly of wave I, was found in 12 ears (11.1%) and a total absence of evoked potentials not always related to the hearing loss, occurred in 5 ears (4.6%).

Effects of sex on auditory brainstem responses in infancy and early childhood

The effects of sex on I-III, III-V and I-V interwave intervals and I, III, V ABR waves latency values have been studied in 171 normal children born at term, 94 males and 77 females, aged between 2 and 720 days. The obtained data confirm that latency values decrease progressively with age, and show that there is a statistically significant difference in wave III and V latency values and in III-V and I-V intervals between males and females. Moreover, these differences seem to increase with age. The authors also discuss the possible underlying mechanisms and claim that even in infancy, sex-related variability should be taken into account.

Effects of high-pass filtering on the waveform and threshold of auditory brainstem responses to tone pips

The authors answer to the comments on their paper 'Auditory Brainstem Responses to middle-and low-frequency tone pips' by Dr. Paul Kileny. Physical characteristics of the stimuli employed, waveform and latency variations using different high-pass filtering (50 and 200 Hz) are discussed.

Middle-latency auditory components in response to clicks and low- and middle-frequency tone pips (0.5-1 kHz)

Middle-latency auditory components (MLC) in response to clicks and tone pips have been recorded in 20 normal subjects, aged between 26 and 32 years, in order to verify their reliability in response to frequency-specific stimuli (0.5 and 1kHz). The results indicate a good reliability of MLC obtained when using tone pips. The responses show the conventionally labeled Po, Na, Nb, Pb waves. The latencies of these waves tend to be greater than those of the corresponding waves elicited by clicks and their amplitudes are smaller. This is probably due to an asynchrony of the responses. The Po and Pa waves are the most resistant to decreasing stimulus intensity, as both are clearly detectable down to 20 dB nHL, but Po is the best threshold index because at 20 dB it has a more clear-cut shape than Pa. According to the latency values obtained for MLC elicited by both clicks and tone pips, the Po wave is probably generated at the inferior colliculus level. The latency shift towards the click-elicited Jewett wave V is mainly due to the different filter settings employed. The morphology of MLC elicited by tone pips is less affected by changes in stimulus frequency than that of corresponding auditory brainstem responses. Thus, MLC are a reliable indicator for defining low- and middle-frequency auditory thresholds.

Auditory brainstem responses to middle- and low-frequency tone pips

Auditory brainstem responses (ABR) evoked by clicks allow a threshold evaluation for the high-frequency range (2-4 kHz) but not for middle and low frequencies (0.5-1 kHz). In 19 normally hearing subjects aged between 24 and 40 years. ABRs have been recorded using clicks and 0.5- and 1-kHz tone pips, with durations of 6 and 3 ms, respectively, and rise-decay times of 3 and 1.5 ms. The input signal was filtered by a passband filter of 20-5 000 Hz. Parameters of tracings elicited by the different kinds of stimuli are compared. Tone-pip ABR morphology does not show the conventional seven peaks but a single large vertex-positive wave. On the ascending branch high-frequency potentials, probably corresponding to the I, II, III and IV-V click-evoked peaks, were visible in some cases, but they rapidly disappeared as the stimulus intensity was decreased. Their 2.3-3 ms greater mean latency values are presumably related to the rise times of the stimuli employed. In terms of bioelectric generators, this large vertex-positive peak probably corresponds to the Jewett V wave. It probably represents a generalized asynchronous dendritic activity. Thus it is possible to obtain ABRs to middle- and low-frequency stimuli. Mean amplitude values of the slow wave are considerably higher than those of the Jewett V wave, but standard deviations are also larger. The positive wave has been identified in response to 1-kHz tone pips in 100% of cases at 30 dB nHL and in 52% of cases at 20 dB, while for 0.5-kHz tone pips in 73.7% of cases at 30 dB and in 57% at 20 dB. On the whole the threshold is located between 15 and 30 dB nHL.

Reference values and characteristics of brain stem audiometry in neonates and children

ABR (Auditory Brainstem Response) delivering the acoustic stimulus both through a headphone (PHN) and in free field (FF), have been recorded in 59 "normal" children divided into four age-related groups: (1) 22 children born at a gestational age ranging between the 36th and the 41st week; (2) 12 with ages ranging from 1 to 6 months; (3) 15 with ages ranging from 6 to 12 months; (4) 10 with ages ranging from 12 to 36 months. Peak latency values obtained with FF technique have been corrected by calculating the delay due to the distance between the loudspeaker and the tested ears (2.04 ms). When using this correction, no statistically significant differences were found between latency values of peaks JI and JV recorded using the two technique. While JI latency values of various groups do not differ significantly, groups 2--and especially group 1--JV latency values are statistically different from those of the 3rd and 4th group. This observation was confirmed by JV--JI interval values. JV wave in neonates (group 1), using PHN technique, is detectable at 60 dB p.e. SPL (82%) while in all other groups at 60 dB this wave is clearly detectable in all children (100%). Using FF technique, JV wave is still visible at 60 dB in 78% of the neonates (group 1) and in almost all children of the other groups. Considering ABR waveform, using PHN technique, in the first two groups only three waves are visible and the first one disappears at about 80 dB, while the typical 4--5 waves of normal adult tracings are detectable since 8--12 months of age. FF tracings instead show three peaks in all groups, the first (JI) being less evident when compared with the one obtained using PHN technique. JV amplitude values observed in FF are higher than those obtained delivering the stimulus through the headphone.