Tony Sirimanna

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.

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.

Surgical Experience With Bone-Anchored Hearing Aids In Children†

Titanium osseointegrated implants for boneanchored hearing aids (BAHAs) have been in use since 1977. A series of 32 children who received implantation since 1990 is reported. The report focuses on the surgical aspects of BAHAs, predisposing factors, and prevention of complications in an unusual pediatric population. The records of 32 children who had undergone two‐stage implantation of a BAHA were retrospectively reviewed. The majority of the patients had craniofacial abnormalities. Of the 32 implantees, 29 use their BAHA at present. Five children failed to achieve osseointe‐gration, and eight patients have had revision surgery for lost abutments, trauma, or chronic skin problems. There were no differences between preimplantation and postimplantation bone or air conduction thresholds. The pediatric BAHA carries with it a unique set of challenges and problems but can be successfully implanted and maintained.

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.

Management of auditory processing disorders

Hearing is one of the cornerstones of human communication. The term ‘Auditory Processing Disorder (APD)’ refers to a hearing disorder resulting from impaired brain function. Diagnosis and management of APD requires a multidisciplinary approach, given the potential impact of APD on listening, communication and academic outcomes, and considering the frequent comorbidity of APD with related language and learning difficulties. Intervention strategies can be divided into five main categories, namely environmental modifications, signal enhancement strategies, teacher/speaker based adaptations, formal and informal auditory training, and compensatory strategies. While outcome studies – other than single case studies – are lacking for informal auditory training and compensatory strategies, these are low-cost procedures that have been long employed in childrens education. There is some recent evidence to suggest that formal auditory training by means of computerized games leads to improvements in phonological awareness and educational performance in these children. However, further research is needed to understand how and why intervention works and which is the most cost-effective intervention for individual cases.

Temporal auditory and visual motion processing of children diagnosed with auditory processing disorder and dyslexia.

Objective: Auditory processing disorder (APD) is diagnosed on the basis of listening difficulties despite normal audiogram, although the cause is unknown. This study examined the hypothesis that the underlying cause of APD is a modality-specific deficit in auditory temporal processing and also considered how far the auditory impairments in APD differ from those in children with dyslexia. Design: Performance of children diagnosed with APD (N = 22) was compared with that of a normative group (N = 98) as well as with children with dyslexia (N = 19) on a battery of temporal auditory tasks; 2-Hz frequency modulation (FM), 40-Hz FM, and iterated rippled noise detection as well as a control task (240-Hz FM), which is thought to draw on peripheral spectral mechanisms. Visual tasks were coherent form and coherent motion detection. Results: On average, the APD group performed more poorly than the normative group on the 40-Hz FM, 240-Hz FM, and iterated rippled noise tasks. There were no significant differences between the APD and dyslexia groups performance and no evidence for a specific temporal auditory impairment. A higher proportion of children in the APD group performed poorly (<−1 SD) on the visual tasks than those in the normative group. Auditory psychophysical performance correlated positively with the performance on the SCAN-C, a standardized test of auditory processing, but not with reading ability. Conclusions: The research did not support a modality-specific impairment of temporal auditory processing as being the underlying cause of APD. In both the APD and dyslexia groups, a similar proportion displayed poor auditory performance, and this does not seem entirely accounted for by attention or performance I.Q. However, the significance of these auditory difficulties is uncertain. Serious difficulties with auditory assessment were also identified. Currently, auditory perceptual deficits may be better seen as a part of a multifactorial description of learning problems rather than as part of a diagnostic category in their own right.

High-frequency audiometry reveals high prevalence of aminoglycoside ototoxicity in children with cystic fibrosis

BACKGROUND Intravenous aminoglycoside (IV AG) antibiotics, widely used in patients with cystic fibrosis (CF), are known to have ototoxic complications. Despite this, audiological monitoring is not commonly performed and if performed, uses only standard pure-tone audiometry (PTA). The aim of this study was to investigate ototoxicity in CF children, to determine the most appropriate audiological tests and to identify possible risk factors. METHODS Auditory assessment was performed in CF children using standard pure tone audiometry (PTA), extended high-frequency (EHF) audiometry and distortion-product otoacoustic emissions (DPOAE). RESULTS 70 CF children, mean (SD) age 10.7 (3.5) years, were recruited. Of the 63 children who received IV AG, 15 (24%) children had ototoxicity detected by EHF audiometry and DPOAE. Standard PTA only detected ototoxicity in 13 children. Eleven of these children had received at least 10 courses of IV AG courses. A 25 to 85 dBHL hearing loss (mean±SD: 57.5±25.7 dBHL) across all EHF frequencies and a significant drop in DPOAE amplitudes at frequencies 4 to 8 kHz were detected. However, standard PTA detected a significant hearing loss (>20 dBHL) only at 8 kHz in 5 of these 15 children and none in 2 subjects who had significantly elevated EHF thresholds. The number of courses of IV AG received, age and lower lung function were shown to be risk factors for ototoxicity. CONCLUSIONS CF children who had received at least 10 courses of IV AG had a higher risk of ototoxicity. EHF audiometry identified 2 more children with ototoxicity than standard PTA and depending on facilities available, should be the test of choice for detecting ototoxicity in children with CF receiving IV AG.

A model of neuronopathic Gaucher disease.

Summary: Gaucher disease (GD) is a lysosomal disorder involving the accumulation of glucocerebroside in the liver, spleen, bones and brain. Some patients exhibit only systemic disease (type I), but others have additional neurological signs which may lead to rapid neurodegeneration in infancy (type II) or take a more intermediate course (type III). Types II and III are collectively known as neuronopathic Gaucher disease (NGD). Systemic disease can now be treated by enzyme replacement therapy (ERT), but its efficacy in NGD is limited. Two infants who presented with bulbar palsy and failure to thrive were enzymatically diagnosed at 8 months with NGD. They were started on high-dose ERT (120 IU/kg every 2 weeks). Both underwent serial oculomotor assessment and an audiological battery, including visual reinforcement audiometry, otoacoustic emissions, and the auditory brain stem response (ABR). Biochemical markers showed an incomplete systemic response to ERT, but neurological deterioration was relentless, leading to death at 16 and 25 months. Oculomotor testing revealed a complete absence of saccadic eye movements and progressive bilateral sixth nerve palsy in one. Audiological assessment revealed progressive deterioration of ABRs, but with normal peripheral hearing and otoacoustic emissions. Both infants showed neurological deterioration in spite of high-dose ERT. The audiological findings suggested a loss of inner hair cell pathway function with preserved outer hair function, similar to what is seen in auditory neuropathy. The unusual pattern of audiological and oculomotor abnormalities is consistent with an excitotoxic mechanism predisposing nerve cells to glucocerebroside toxicity. Such excitotoxic damage may be amenable to direct therapeutic intervention.

Aminoglycoside antibiotics cochleotoxicity in paediatric cystic fibrosis (CF) patients: A study using extended high-frequency audiometry and distortion product otoacoustic emissions

Abstract Despite known ototoxic effects of aminoglycoside (AG) antibiotics, audiological assessment is not routinely undertaken in UK CF patients. Consequently, the incidence of hearing loss is not well established. Objective: To document the incidence of hearing loss in cystic fibrosis (CF) children. Design: Hearing function of 45 children from Great Ormond Street Hospital was assessed using pure-tone audiometry up to 20kHz and DPOAEs up to 8kHz. Study Sample: 39/45 of participants had received intravenous (IV) AGs, 23 of which received repeated IV AGs every 3 months. Results: In this high exposure group, 8 (21%) had clear signs of ototoxicity; average 8-20kHz thresholds were elevated by ∼50dB and DPOAE amplitudes were >10dB lower at f2 3.2-6.3 kHz. The remaining 31/39 (79%) of AG exposed patients had normal, even exceptionally good hearing. The 21% incidence of ototoxicity we observed is substantial and higher than previously reported. However, our finding of normal hearing in children with equal AG exposure strongly suggests that other unknown factors, possibly genetic susceptibility, influence this outcome. Conclusions: We recommend comparable auditory testing in all CF patients with high AG exposures. Genetic analysis may help explain the dichotomy in response to AGs found. Sumario A pesar de los conocidos efectos ototóxicos de los antibióticos aminoglucósidos (AG), en el Reino Unido no se lleva a cabo de rutina una evaluación audiológica en los pacientes con fibrosis quística (CF); consecuentemente, la incidencia de hipoacusia no está bien establecida. Objetivo: Documentar la incidencia de trastornos auditivos en niños con fibrosis quística (CF). Diseño: Se evaluó la función auditiva de 45 niños del Hospital Great Ormon Street, usando audiometría de tonos puros hasta 20kHz y DPOAE hasta 8 kHz. Muestra Del Estudio: 39/45 participantes habían recibido AG intravenosos (IV), 23 de los cuáles los recibieron repetidamente por vía IV, cada 3 meses. Resultados: En este grupo de alta exposición, 8 niños (21%) mostraban claros signos de ototoxicidad; los umbrales promedio de 8-20 kHz estaban elevados por ∼50dB y las amplitudes de las DPOAE estaban >10dB más bajas en f2 3.2-6.3 kHz. Los restantes 31/39 (79%) pacientes expuestos a AG tenían una audición normal e incluso, excepcionalmente buena. La incidencia de ototoxicidad del 21% que observamos es sustancial y es más alta de lo previamente reportado. Sin embargo, nuestro hallazgo de audición normal en niños con exposición equivalente a AG sugiere fuertemente que otros factores desconocidos, posiblemente la susceptibilidad genética, influyen en los resultados. Conclusiones: Recomendamos evaluaciones auditivas similares en todos los pacientes con CF con alta exposición a AG. El análisis genético puede ayudar a explicar la dicotomía encontrada en cuanto a la respuesta a AG.

Useful residual hearing despite radiological findings suggestive of anacusis.

A severe malformation of the inner ear, often referred to as severe labyrinthine dysplasia or common cavity deformity, consists of an absent or dilated cochlear basal coil, wide communication with the vestibule and a tapered internal acoustic meatus and can be associated with absent hearing. We discuss two children with severe labyrinthine dysplasia as shown by computed tomography (CT) scans and, in the first case, an absent VIIIth nerve bilaterally shown by magnetic resonance imaging (MRI). In 1995, both cases were precluded from cochlear implantation, on the basis of the absent VIIIth nerve (first case) and increased risk of CSF leak during operation (second case). However, audiometric results and vocalization patterns of both children suggested the presence of some residual hearing function, while recently reported specific surgical techniques have been found to be safe and effective in the cochlear implantation of the common cavity deformity. The management of such cases should be decided on the grounds of a full audiological assessment in conjunction with the radiological features, in the light of current surgical trends shown to be safe and effective.