Evolution of Italian Universal Newborn Hearing Screening Programs.

BACKGROUND: The aim of this study was to evaluate the state of implementation of the Universal Newborn Hearing Screening Programs in Italy and to determine the effect that an ad hoc legislation may have on the percentage of infants screened for detection of hearing impairment in nurseries. MATERIAL AND METHODS: Italian Newborn Hearing Screening data were obtained during four national surveys (years 2003, 2006, 2008, and 2011). The screening rates obtained by the Regions which adopted or did not adopt a legislation to increase the newborns' coverage were compared. RESULTS: In 2011, the average coverage rate was 78.3%, but in 12 out of 20 Regions it exceeded 95%. Coverage rate was greater in Regions that implemented an ad hoc legislation compared to Regions that did not. As a matter of fact, Regions which passed the legislation screened more than 95% of infants, whereas Regions without legislation reported a mean screening rate of nearly 67% of newborns. CONCLUSION: Current results seem to confirm that a specific legislation might have a decisive effect on the increase of rate of coverage of newborn hearing screenings.

Influence of cochlear implant-like operating conditions on wavelet speech processing.

This study assessed the influence of 'non-ideal' operating conditions typical of cochlear implants (CIs) on the behavior of the wavelet transform (WT) when used to process speech. Particular attention was given to the effect of limited stimulation rate and limited number of channels, typical of CI speech processing, on the performance of the WT. Computer simulations and psychoacoustic recognition tests of WT-processed speech were implemented. The crucial role played by the 'non-ideal' operating conditions on WT speech processing was put in evidence. Psychoacoustic recognition tests proved to be fundamental to evaluate feasibility of WT speech processing for CIs.

Field analysis of auditory evoked brainstem potentials.

Surface distribution maps of auditory evoked brainstem potentials (AEBPs) are presented for time instants corresponding to the waves of major interest (I, III and V) in humans. Maps are shown to be fully consistent with the results of two approaches that have been recently proposed for the analysis of AEBPs, namely dipole localization methods and three-channel Lissajous trajectories, thus confirming the technical feasibility of methods for extracting information on the sources of AEBPs from surface data.

Theoretical and experimental analysis of a central optimal processor for pitch of multicomponent inharmonic tones.

This paper describes some experiments on the pitch produced by multicomponent tones. Stimuli used were the sum of a pure tone at frequency f = 1 kHz and of the first six successive subharmonics at frequencies psi i = f/i (i = 2, 3, 4, 5, 6, 7) or, in separate experiments, the sum of six (i = 2, 3, 4, 5, 6, 7), five (i = 3, 4, 5, 6, 7) or four (i = 4, 5, 6, 7) subharmonics, respectively. Pitch data produced by these stimuli have been compared with the predictions of the optimum processor theory developed by Goldstein and coworkers (Goldstein, J.L. (1973): J. Acoust. Soc. Am. 54, 1496-1516; Goldstein, J.L. et al. (1978): J. Acoust. Soc. Am. 63, 486-497; Gerson, A. and Goldstein, J.L. (1978): J. Acoust. Soc. Am. 63, 498-510). Model predictions are shown to deviate significantly from the experimental results. By assuming the existence of an additional transformation to be included into the original mathematical model, without any other modification, predictions are in complete agreement with pitch data.

Time-frequency distributions of click-evoked otoacoustic emissions.

Emissions evoked by broad-band stimuli, such as clicks, show a 'frequency dispersion' reminiscent of the place-frequency distribution along the cochlea. Analysis of the time-frequency properties of transiently evoked otoacoustic emissions (TEOAEs) is therefore of considerable interest due to their close relation with cochlear mechanisms. In particular, since OAEs in response to click stimuli are expected to evoke a cumulative response from the whole cochlea, the analysis of click-evoked OAEs can yield a global view of cochlear function. Wavelet analysis is performed to obtain time-frequency distributions of click-evoked OAEs at various intensity levels from normal ears. By means of the inverse wavelet transform, the recorded responses are decomposed into elementary components representing the contribution within a narrow frequency band to the cumulative OAE. The relationship between the frequency of the elementary components, latency and level of stimulation is described.

Frequency and temporal analysis of contralateral acoustic stimulation on evoked otoacoustic emissions in humans.

Previous studies have shown that the effect of contralateral acoustic stimulation (CAS) on ipsilateral evoked otoacoustic emissions (EOAE) depends somewhat upon the spectrum of the eliciting stimulus. The latency of the EOAE, however, is itself frequency-dependent. Consequently, two general ways of analyzing the effects of CAS may be considered: by frequency band or by temporal segment. In this study, we analyzed the effects of CAS both ways in the same subjects, essentially simultaneously. The frequency analysis of the EOAE derived from the wavelet transform (WT). The WT is known to provide a robust approach to the analysis of non-stationary signals and was anticipated to avoid possible time-frequency confounds of the cochlear mechanical system. For comparison, a more basic analysis - using a temporal moving window - was employed. The results largely support earlier findings and confirm that in humans the greatest suppression of EOAEs by CAS is obtained for lower frequency and/or longer latency EOAE components. Despite expectations for the WT analysis, the more basic, temporal, analysis tended to yield the clearer results.

Magnetic stimulation of the motor cortex--theoretical considerations.

The aim of this paper is to present a first approximation model for the computation of the electric fields produced in the brain tissues by magnetic stimulation. Results are given in terms of induced electric field and current density caused by coils of different radii and locations. Nontraditional coil locations and assemblies are also considered (multicoil arrangements). Model simulations show that a good control of the excitation spread can be achieved by proper positioning of the coil. It is also predicted that one of the major drawbacks of the technique, i.e., the poor ability to concentrate the current spread into a small brain area can be partially overcome by more effective coil positioning and/or assembly. Finally, some comparisons are made among the results obtained from electric and magnetic stimulation. This is thought to be of great help in the design of experiments aimed to understand the relative role of the different brain structures responsible for the motor response.

Evoked otoacoustic emissions: nonlinearities and response interpretation.

Evoked otoacoustic emissions (EOAE's) are acoustic signals produced by the inner ear in response to transient acoustic stimuli and can be recorded in the external auditory canal. Since emissions can be reduced or even abolished by hearing losses of peripheral origin due to trauma and pathology, EOAE's are presently considered as the most sensitive clinical test for assessing the integrity of peripheral hearing. Recordings of emissions evoked in response to transient stimuli are contaminated by an initial artifact which in most clinical environments can be a very serious limitation. For this reason, a nonlinear estimation method is widely used (derived nonlinear response, DNLR), instead of classical synchronous averaging. Aims of this paper are: i) to justify theoretically the use of the DNLR technique by means of a simple model; ii) to compare the results obtained from the classical averaging (a linear estimation technique) with those obtained from the nonlinear DNLR technique. Some suggestions of practical interest are finally inferred from present analysis.

An analytical model to predict the electric field and excitation zones due to magnetic stimulation of peripheral nerves.

The main unknown factor in understanding magnetic stimulation of peripheral nerves is the distribution of the induced electric field. We have applied the so-called reciprocity theorem and developed an analytical model to compute the electric field and its spatial derivatives inside pseudocylindrical structures. The results can be used to predict the site of excitation in magnetic stimulation of peripheral nerves.

Wavelet analysis of click-evoked otoacoustic emissions.

Time-frequency distribution methods are being widely used for the analysis of a variety of biomedical signals. Recently, they have been applied also to study otoacoustic emissions (OAE's), the active acoustic response of the hearing end organ. Click-evoked otoacoustic emissions (CEOAE's) are time-varying signals with a clear frequency dispersion along with the time axis. Analysis of CEOAE's is of considerable interest due to their close relation with cochlear mechanisms. In this paper, several basic time-frequency distribution methods are considered and compared on the basis of both simulated signals and real CEOAE's. The particular structure of CEOAE's requires a method with both a satisfactory time and frequency resolution. Results from simulations and real CEOAE's revealed that the wavelet approach is highly suitable for the analysis of such signals. Some examples of the application of the wavelet transform to CEOAE's are provided here. Applications range from the extraction of normative data from adult and neonatal OAE's to the extraction of quantitative parameters for clinical purposes.

Two-dimensional filter to facilitate detection of transient-evoked otoacoustic emissions.

This paper implements a filtering technique to enhance the signal-to-noise ratio (SNR) and, in turn, the detection of transient-evoked otoacoustic emissions (TEOAE's), generated by healthy human cochlea. One can increase the SNR by compiling an image of recorded TEOAE from more than one stimulus intensity, averaged over a few sweeps, which can be further processed by means of two-dimensional spatial mean filters. Averaging some 60 sweeps recorded to stimuli at several intensity levels requires one-forth of the collection time needed for a classical set of responses (average of 260 sweeps), and obtains approximately the same final SNR. The relation between the performances of the proposed technique and the SNR of the rapidly acquired responses before filtering is also investigated.

Theory of multichannel magnetic stimulation: toward functional neuromuscular rehabilitation.

Human excitable cells can be stimulated noninvasively with externally applied time-varying electromagnetic fields. The stimulation can be achieved either by directly driving current into the tissue (electrical stimulation) or by means of electro-magnetic induction (magnetic stimulation). While the electrical stimulation of the peripheral neuromuscular system has many beneficial applications, peripheral magnetic stimulation has so far only a few. This paper analyzes theoretically the use of multiple magnetic stimulation coils to better control the excitation and also to eventually mimic electrical stimulation. Multiple coils allow electronic spatial adjustment of the shape and location of the stimulus without moving the coils. The new properties may enable unforeseen uses for peripheral magnetic stimulation, e.g., in rehabilitation of patients with neuromuscular impairment.

A volume-conduction analysis of magnetic stimulation of peripheral nerves.

Magnetic stimulation is a method to study several nervous disorders as well as the intact nervous system in humans. Interest in magnetic stimulation of peripheral nerves has grown rapidly, but difficulties in locating the site of excitation have prevented it from becoming a routine clinical tool. It has been reasoned that the activating function of long and straight nerves is the first spatial derivative of the electric field component parallel to the nerves. Therefore, to predict the site of activation, one has to compute this field feature. We describe here an analytical mathematical model and investigate the influence of volume-conductor shape on the induced field. Predictions of the site of activation are given for typical stimulation coil arrangements and these results are compared with experimental and literature data. Comparisons suggest that the activating function is not simply the spatial gradient of the induced electric field, but that other mechanisms are also involved. The model can be easily utilized in the search for more efficient coil constructions and improved placements with respect to the target nerves.

Temporal segmentation and multiple-source analysis of short-latency median nerve SEPs.

Short-latency (10-50 ms) median nerve somatosensory evoked potentials (SEPs) from four normal subjects were analysed by means of temporal segmentation techniques and source derivation methods. In each case the responses were recorded using 32 electrodes. Dipolar optimization was carried out with a time-varying technique, using three different approaches: regional source estimation, spherical source estimation (one radial and one tangential component), and multiple dipolar approach. This was to assess the relative influence on the dipolar solution of the different optimization techniques. The effect of the different number of channels in the estimation procedures has been also investigated. The methods of optimization are crucial, particularly for the orientation of P22. In all cases the source location estimated with the 32-electrode montage was shifted towards the centre of the spheres.

Time-frequency distribution methods for the analysis of click-evoked otoacoustic emissions.

Click-evoked otoacoustic emissions (CEOAEs) are time-varying signals with a clear frequency dispersion along with the time axis. Analysis of CEOAEs is of considerable interest due to their close relation with cochlear mechanisms. The particular structure of CEOAEs requires a time-frequency method with both a satisfactory time and frequency resolution. In this paper, several basic time-frequency distribution methods are considered and compared on the basis of both simulated signals and real CEOAEs. Results from simulations and real CEOAEs revealed that the wavelet approach is highly suitable for the analysis of such signals. Some examples of the application of the Wavelet Transform to CEOAEs are provided here. Applications range from the extraction of normative data from adult OAEs to the extraction of quantitative parameters for clinical purposes.

High resolution time-frequency analysis of otoacoustic emissions.

High resolution time-frequency analysis of OAE signals evoked by stimuli of different strength was performed by means of the Matching Pursuit algorithm. The method relies on adaptive decomposition of a signal into waveforms of well-defined frequency and time localization. Energy of OAE as a function of time and frequency was evaluated for stimuli strength of 35-80 dB SPL. Dynamic characteristics of the signal were constructed. For strong stimuli decrease of the power of high frequency components was found. Matching Pursuit proved to be a method which offers high resolution parametrisation of OAE in time-frequency space and provides excellent possibilities of investigation of the signal generation mechanisms.

Analysis of temporal non-stationarities in EEG signals by means of parametric modelling.

A method for the analysis of variability of EEG signals is described. We examined simulated signals and real EEGs obtained from a normal subject and two epileptic patients. The first step of the method is based on autoregressive (AR) modelling of short EEG epochs. Prediction coefficients of the AR model were computed as a function of time from partially-overlapping moving windows of 2 s duration. The temporal behaviour of these coefficients was analysed to detect variability: quasi-stationary activity causes only smooth changes in the coefficients while variations in the amplitude and/or the frequency content of the signal are shown to produce sharp changes in the coefficients. A segmentation algorithm was developed to detect and quantify with a numerical value (Difference Measure, DM) the AR coefficients variations.

Adult hearing screening: follow-up and outcomes1.

PURPOSE: To screen hearing and evaluate outcomes in community-dwelling older adults. METHOD: Three thousand and twenty-five adults responded to an invitation to be screened by questionnaire, otoscopy, and pure-tone audiometry. Pure-tone average (PTA) >35 dB HL in the worse ear, unilateral hearing loss, or otoscopic findings were the criteria for referral for services. A questionnaire related to compliance with referral recommendations was completed by telephone interview for 160 randomly selected participants after 1-2 years from referral. RESULTS: The referral rate for audiologic/hearing aid evaluation was 46%, and referral for cerumen removal/medical evaluation was 17%. Of the people referred for audiologic/hearing aid evaluation, 18% tried a hearing aid; 2 years later, 11% were using a hearing aid. Screening recommendations affected participants' decision to seek help. Study participants stated that the screening was helpful, it should be offered to everybody, and they would participate in future screenings. CONCLUSION: Although adult hearing screening offered timely identification of hearing loss for adults seeking help, follow-up with hearing aid treatment was low.

SUN-test (Speech Understanding in Noise): A Method for Hearing Disability Screening.

The SUN-test (Speech Understanding in Noise) is a speech-in-noise test to screen adults and older adults for hearing disability. The SUN-test consists in a short list of intervocalic consonants (VCV, vowel-consonant-vowel) in noise that are presented in a three-alternatives forced choice (3AFC) paradigm by means of a touch-screen interface. Based on the number of stimuli correctly identified, the tested subject gets one of three possible test outcomes: no listening difficulties, a hearing check would be advisable, or a hearing check is recommended. This paper reviews the main results obtained with the SUN-test in the Italian language in a population of nearly 1,300 adults and older adults with varying degrees of audiometric thresholds and audio-metric configurations, tested both in low and in high ambient noise settings. Results obtained in the tested population revealed that the outcomes of the SUN-test were in line with the outcomes of pure-tone testing, and that the test performance was similar both in low and in high ambient noise (up to 65 dB A). Results obtained with the SUN-test were not biased by the age of the subject because the performance of younger and older subjects in the test was similar. The mean duration of the SUN-test was nearly 40 s/ear, and was lower than 1 minute per ear even in subjects older than 80 years so that both ears could be tested, on average, in 2 minutes. The SUN-test was considered easy or slightly difficult by nearly 90% of subjects; test duration was judged short or fair by nearly 95% of subjects, and the overall evaluation of the test was pleasant, or neutral, in more than 90% of subjects. Overall, results of this study indicated that the SUN-test might be feasible for application in adult hearing screening. The test is fast, easy, self convincing, and reflects differences in hearing sensitivity between the tested subjects. The outcomes of the SUN-test were not influenced by the noise level in the test room (up to 65 dB A) indicating that the test, as such, might be feasible to screen adults and older adults both in clinical and in non clinical settings, such as convenient care clinics, hearing aid providers, or pharmacies, where the ambient noise is, typically, not controlled.

Pilot Initiatives of Adult Hearing Screening in Italy.

A series of pilot initiatives of adult hearing screening programs were organized in eight large and small-size cities in Italy in the past two years. The screening initiatives were held in public places, supermarkets, drugstores, and in some universities of the third age, and involved an overall population of 2,278 screened subjects with age ranging from 13 to 93 years. Three different screening tests were used to assess hearing ability in the participants, i.e.: screening pure tone audiometry (PTA), an automated speech-in-noise screening test (the SUN-test), and a screening questionnaire of self-perceived hearing handicap (the HHIE-S). This paper describes the organization and management of these screening initiatives and reviews the main results obtained in the screened population, using the three different screening tests. Results obtained in these pilot initiatives showed that screening adults for hearing problems might be feasible, on a local level, in non clinical settings and can be performed quite easily with the support of local coordinators and partners, such as associations or local authorities. It is recognized that further initiatives and studies will have to be performed to better define the key aspects related to the organization and management of adult hearing screening programs, either at a local, regional, or national level.