Doris-Eva Bamiou

Gin (gaps-in-noise) Test Performance In Subjects With Confirmed Central Auditory Nervous System Involvement

Objective: The purpose of the present study was to investigate the value of a new gap detection procedure called Gaps-In-Noise (GIN) for assessment of temporal resolution in a clinical population. Design: The test consists of 0 to 3 silent intervals ranging from 2 to 20 msec embedded in 6-sec segments of white noise. The location, number, and duration of the gaps per noise segment vary throughout the test for a total of 60 gaps presented in each of four lists. The GIN procedure was administered to 50 normal-hearing listeners (group I) and 18 subjects with confirmed neurological involvement of the central auditory nervous system (group II). Results: Results showed mean approximated gap detection thresholds of 4.8 msec for the left ear and 4.9 msec for the right ear for group I. In comparison, results for group II demonstrated a statistically significant increase in gap detection thresholds, with approximated thresholds of 7.8 msec and 8.5 msec being noted for the left and right ears, respectively. Significant mean differences were also observed in the overall performance scores (i.e., the identification of the presence of the gaps within the noise segments) of the two groups of subjects. Finally, psychometric functions, although similar for short and long duration gaps, were highly different for gaps in the 4- to 10-msec range for the two groups. Conclusions: A variety of psychoacoustic procedures are available to assess temporal resolution; however, the clinical use of these procedures is minimal at best. Results of the present study show that the GIN test holds promise as a clinically useful tool in the assessment of temporal resolution in the clinical arena.

Aetiology and clinical presentations of auditory processing disorders--a review.

Auditory processing disorders may have detrimental consequences on a childs life, if undiagnosed and untreated. We review causes of auditory processing disorders in order to raise clinical awareness. Auditory processing disorders may present against a background of neurological disease or developmental disorders, as well as in isolation. Clinicians need to be aware of potential causes and implications of auditory processing disorders.

The insula (Island of Reil) and its role in auditory processing

The insular cortex is a complex structure which contains areas that subserve visceral sensory, motor, vestibular, and somatosensory functions. The role of the insular cortex in auditory processing was poorly understood until recently. However, recent case studies indicate that bilateral damage to the insulae may result in total auditory agnosia. Functional imaging studies demonstrate that the insulae participate in several key auditory processes, such as allocating auditory attention and tuning in to novel auditory stimuli, temporal processing, phonological processing and visual-auditory integration. These studies do not clarify the issue of further specialisation within the insular cortex, e.g. whether the posterior insulae are primarily sensory areas, while the anterior insulae serve mainly as integration/association auditory areas, two hypotheses that would be compatible with the cytoarchitectonic structure and connectivity of the insulae. The functional characterisation of the insulae remains incomplete, underlining the need for further studies.

Profile and aetiology of children diagnosed with auditory processing disorder (APD)

OBJECTIVE Auditory processing disorder (APD) is characterised by listening difficulties despite a normal audiogram. APD is becoming ever more widely diagnosed in children, though there is a controversy over definition, diagnosis and aetiology. This study sought to describe presenting features and investigate aetiological factors for children diagnosed with APD compared to those for whom APD was excluded. METHODS Medical notes for children referred to a specialist hospital-based APD clinic were reviewed in relation to presenting features and potential aetiological factors. RESULTS 32 children diagnosed with APD and 57 non-APD children were compared. They reported similar symptoms and similarly had high rates of co-morbid learning problems. No aetiological factor (including history of otitis media, adverse obstetric history or familial history of listening problems) predicted APD group membership. CONCLUSIONS Children identified with APD on the basis of commonly used APD tests cannot be distinguished on the basis of presenting features or the aetiological factors examined here. One explanation is that learning problems exist independently of auditory processing difficulties and the aetiological factors do not have a strong causal role in APD. However, no gold standard for APD testing exists and an alternative explanation is that the commonly used APD tests used as selection criteria in this study may be unreliable.

Auditory temporal processing deficits in patients with insular stroke

Objective: To assess central auditory function in a series of patients with stroke of the insula and adjacent areas. Methods: The authors recruited eight patients with stroke affecting the insula and adjacent areas and eight neurologically normal controls (matched to the patients for age, sex, handedness, and hearing thresholds). The lesion spared the adjacent auditory areas in three patients and included other auditory structures in five cases. The authors conducted pure-tone audiometry and tympanometry and a central auditory test battery, which included the dichotic digits, and three temporal tests, the duration pattern, frequency pattern, and gaps in noise tests. They collected information from the hospital notes on symptoms at presentation and neuropsychological assessment data during the acute phase. Results: The central auditory tests gave normal results in all controls. The temporal tests gave abnormal results in all three cases in which other auditory areas were spared, as well as in the other five cases. Results of the gaps in noise test were abnormal contralaterally to the lesion in three and bilaterally in five cases. The central auditory deficits did not cosegregate with the presence of cognitive impairment during the acute stage. Conclusion: Insular lesions may affect central auditory function and, in particular, temporal resolution and sequencing, consistent with neuroimaging studies.

Non-verbal sound processing in the primary progressive aphasias

Little is known about the processing of non-verbal sounds in the primary progressive aphasias. Here, we investigated the processing of complex non-verbal sounds in detail, in a consecutive series of 20 patients with primary progressive aphasia [12 with progressive non-fluent aphasia; eight with semantic dementia]. We designed a novel experimental neuropsychological battery to probe complex sound processing at early perceptual, apperceptive and semantic levels, using within-modality response procedures that minimized other cognitive demands and matching tests in the visual modality. Patients with primary progressive aphasia had deficits of non-verbal sound analysis compared with healthy age-matched individuals. Deficits of auditory early perceptual analysis were more common in progressive non-fluent aphasia, deficits of apperceptive processing occurred in both progressive non-fluent aphasia and semantic dementia, and deficits of semantic processing also occurred in both syndromes, but were relatively modality specific in progressive non-fluent aphasia and part of a more severe generic semantic deficit in semantic dementia. Patients with progressive non-fluent aphasia were more likely to show severe auditory than visual deficits as compared to patients with semantic dementia. These findings argue for the existence of core disorders of complex non-verbal sound perception and recognition in primary progressive aphasia and specific disorders at perceptual and semantic levels of cortical auditory processing in progressive non-fluent aphasia and semantic dementia, respectively.

Temporal bone computed tomography findings in bilateral sensorineural hearing loss

AIM To examine the yield of computed tomography (CT) of the temporal bones when investigating sensorineural hearing loss (SNHL) and to identify factors associated with CT findings. METHODS Retrospective analysis of 116 consecutively investigated children with bilateral SNHL at the audiology department of Great Ormond Street Hospital, London. Main outcome measures were CT results, hearing loss parameters, history, and clinical examination. RESULTS A total of 33 (28.4%) CT scans were identified as abnormal. Children with profound and/or progressive hearing loss and/or craniofacial abnormalities were more likely to have an abnormal CT scan and together accounted for 25 abnormal CT scans. Sex, consanguineous parents, or family history of SNHL were not associated with CT findings. Dilated vestibular aqueduct was significantly correlated with the presence of progressive SNHL. CONCLUSIONS All children with SNHL should undergo radiological investigation of the petrous bones/inner ear; abnormalities are more likely to be found in cases with craniofacial abnormalities, or profound or progressive hearing loss. The decision whether to perform a CT or magnetic resonance imaging will depend on scanner availability, expertise, and management considerations, but cochlear implant candidates will require both.

Evolving concepts of developmental auditory processing disorder (APD): a British Society of Audiology APD special interest group 'white paper'.

Abstract Children with listening difficulties, but normal audiometry, may be diagnosed with APD. The diagnosis is typically based on poor performance on tests of perception of both non-speech and speech stimuli. However, non-speech test results correlate only weakly with evaluations of speech-in-noise processing, cognitive skills, and caregiver evaluations of listening ability. The interpretation of speech test results is confounded by the involvement of language processing mechanisms. Overall, listening ability is associated more with higher-level, cognitive and analytic processing than with lower-level sensory processing. Current diagnosis of a child with APD, rather than another problem (e.g. language impairment, LI), is determined more by the referral route than by the symptoms. Co-occurrence with other learning problems suggests that APD may be a symptom of a more varied neurodevelopmental disorder. Alternately, APD has been proposed as a cause of language-based disorders, but there is no one-to-one mapping between listening and language among individuals. Screening for APD may be most appropriately based on a well-validated, caregiver questionnaire that captures the fundamental problem of listening difficulties and identifies areas for further assessment and management. This approach has proved successful for LI, and may in future serve as a metric to help assess other, objective testing methods. Foreword Auditory processing disorder (APD) has a long (> 30 years) and controversial history. The controversies concern absolutely fundamental issues: the definition of APD, its neural basis, test validity and standardization, differentiation from other disorders, and even whether it exists as an independent disorder (19). To evaluate and interpret the scientific evidence on APD, and to advise the audiology profession, the British Society of Audiology (BSA) established a Special Interest Group (BSA SIG) on APD in 2003. That group has recently published two key documents, a ‘Position Statement’ and a ‘Management Overview’ (45. See www.thebsa.org.uk ‘Procedures and Publications’). In formulating the new position statement, it became clear to the group that several significant differences were developing between their interpretation of the evidence concerning APD and that of the 1, as stated in their recently published ‘Guidelines for the diagnosis, treatment and management of children and adults with central auditory processing disorder’ (1). To address these differences, and borrowing from British Parliamentary procedure, the BSA SIG decided to develop a ‘white paper’, a discussion document that could then receive an international set of commentaries from other research groups working on APD. An approach was made to the editor of the International Journal of Audiology who agreed to this suggestion. This paper, and the associated commentaries that follow, are the result.

Evidence for a neurophysiologic auditory deficit in children with benign epilepsy with centro-temporal spikes

Summary.Benign focal epilepsy in childhood with centro-temporal spikes (BECTS) is one of the most common forms of epilepsy. Recent studies have questioned the benign nature of BECTS, as they have revealed neuropsychological deficits in many domains including language. The aim of this study was to investigate whether the epileptic discharges during the night have long-term effects on auditory processing, as reflected on electrophysiological measures, during the day, which could underline the language deficits. In order to address these questions we recorded base line electroencephalograms (EEG), sleep EEG and auditory event related potentials in 12 children with BECTS and in age- and gender-matched controls. In the children with BECTS, 5 had unilateral and 3 had bilateral spikes. In the 5 patients with unilateral spikes present during sleep, an asymmetry of the auditory event related component (P85-120) was observed contralateral to the side of epileptiform activity compared to the normal symmetrical vertex distribution that was noted in all controls and in 3 the children with bilateral spikes. In all patients the peak to peak amplitude of this event related potential component was statistically greater compared to the controls. Analysis of subtraction waveforms (deviant – standard) revealed no evidence of a mismatch negativity component in any of the children with BECTS. We propose that the abnormality of P85-120 and the absence of mismatch negativity during wake recordings in this group may arise in response to the long-term effects of spikes occurring during sleep, resulting in disruption of the evolution and maintenance of echoic memory traces. These results may indicate that patients with BECTS have abnormal processing of auditory information at a sensory level ipsilateral to the hemisphere evoking spikes during sleep.

Single-subject oscillatory gamma responses in tinnitus

This study used magnetoencephalography to record oscillatory activity in a group of 17 patients with chronic tinnitus. Two methods, residual inhibition and residual excitation, were used to bring about transient changes in spontaneous tinnitus intensity in order to measure dynamic tinnitus correlates in individual patients. In residual inhibition, a positive correlation was seen between tinnitus intensity and both delta/theta (6/14 patients) and gamma band (8/14 patients) oscillations in auditory cortex, suggesting an increased thalamocortical input and cortical gamma response, respectively, associated with higher tinnitus states. Conversely, 4/4 patients exhibiting residual excitation demonstrated an inverse correlation between perceived tinnitus intensity and auditory cortex gamma oscillations (with no delta/theta changes) that cannot be explained by existing models. Significant oscillatory power changes were also identified in a variety of cortical regions, most commonly midline lobar regions in the default mode network, cerebellum, insula and anterior temporal lobe. These were highly variable across patients in terms of areas and frequency bands involved, and in direction of power change. We suggest a model based on a local circuit function of cortical gamma-band oscillations as a process of mutual inhibition that might suppress abnormal cortical activity in tinnitus. The work implicates auditory cortex gamma-band oscillations as a fundamental intrinsic mechanism for attenuating phantom auditory perception.