Microtia and aural atresia
Clefts and Craniofacial Malformations
Children with cleft lip and palate or cleft palate only or other craniofacial malformations have a high incidence of conductive hearing loss from otitis media with effusion (Swibel Rosenthal et al. 2012). The majority of children develop normal hearing by school age with palatoplasty and routine tube insertion. Hearing improves significantly from childhood to adolescence in patients with cleft lip and palate and cleft palate only.
Syndromal Conductive Hearing Impairment
This type includes various ossicular chain malformations and abnormalities in combination with hearing loss from otitis media with effusion. In many syndromes the auricle is also dysplastic, and the fitting of normal behind-the-ear hearing aids is impossible. The children need bone-anchored hearing aids fixed by a softband for babies and infants. The most common syndromes are Goldenhar syndrome, Treacher Collins syndrome, Pierre Robin syndrome and craniofacial dysostoses (Apert syndrome, Pfeiffer syndrome, Crouzon disease) (Swibel Rosenthal et al. 2012) (see Sect. 14.11).
Abnormalities of the Tympanic Membrane and the Middle Ear
Audiological abnormalities may include the following audiometry: air-bone gap <60 dB, depending on the degree of abnormality of the ossicular transmission, flattened tympanogram, and absence of stapedius reflexes. The most common causes are infections of the middle ear in different stages:
Acute Otitis Media
Acute infections of the middle ear are frequently associated with upper respiratory infections; the typical pathogenic agent is Pneumococcus, Haemophilus influenza or Moraxella. In the literature different evidence-based recommendations exist, particularly those of the current American guidelines for medical treatment (Venekamp et al. 2013).
Chronic Otitis Media
(a) Chronic Otitis media with subtotal perforation of tympanic membrane. (b) Cholesteatoma with epitympanal perforation
Otitis Media with Effusion
Otitis media with effusion
Otosclerosis and Tympanosclerosis
In children otosclerosis is rarely reported. Typically a conductive hearing loss is seen early with a reduced air-bone gap at 2 kHz; later a sensorineural hearing loss may be seen as well. In this age group, the diagnosis is usually suggested by a positive family history of otosclerosis but must be distinguished from more frequent aetiologies of stapes ankylosis with a normal tympanic membrane, such as tympanosclerosis of the oval window or minor aplasia (Lescanne et al. 2008).
Trauma
Fracture of the petrous temporal bone
15.1.3 Sensorineural Hearing Loss
A sensorineural hearing loss affects the inner ear (cochlea) or auditory nerve (eighth cranial nerve). Most sensorineural hearing losses are sensory and restricted to the cochlea and do not result from an abnormality of the auditory nerve. Routine audiometric testing does not differentiate between a sensory loss and a neural loss. Electrophysiological measures (auditory brainstem response, ABR; Cochlear Microphonics, CM) and otoacoustic emissions (OAE) reveal the difference between sensory and neural causes (Gifford et al. 2009; Gregg et al. 2004; Harlor and Bower 2009). Imaging studies by MRI (magnetic resonance imaging) and CT (computed tomography) show congenital malformations of the inner ear: cochlear hypoplasia, incomplete partition, common cavity or enlarged vestibular aqueduct (Huang et al. 2012). In 1987 Jackler published a classification system for congenital malformation of the inner ear (Jackler et al. 1987). Sensorineural hearing loss ranges from mild to profound degree and needs early fitting with hearing aids or cochlear implants, according to audiological test results. In addition, infants with congenital hearing loss benefit from special education with training for speech and language development.
Genetic hearing impairment (see Sect. 14.10)
Chromosomal abnormalities: Down syndrome and Turner’s syndrome (see Sect. 14.11)
Pre-/perinatal factors: low birth weight, hypoxia, hyperbilirubinaemia (see Sect. 14.7)
Prenatal infections: rubella, cytomegalovirus infection, toxoplasmosis, lues, herpes simplex (see Sects. 14.7 and 14.8)
Postnatal infections: meningitis, encephalitis, mumps, measles, chicken pox, influenza (see Sects. 14.7 and 14.8)
The most common major sequela of meningitis is hearing loss to different degrees with overall worldwide prevalence among meningitis patients of 20%, in Europe 9%. Twenty percent of all patients have multiple impairments: hearing loss, seizures, hydrocephalus, spasticity/paresis, cranial nerve palsies and visual impairment (Edmond et al. 2010). The prevalence of bilateral hearing loss of at least 70 dB HL after pneumococcal meningitis with the risk of ossification of the labyrinth system in high-income countries is 8%, and for hearing loss of at least 30 dB HL in one ear, the prevalence increases to 26% (Jit 2010). In the literature it is also reported that the risk of sequelae in children aged less than 5 years is twice as high as for older people (Edmond et al. 2010).
Ototoxicity: aminoglycosides affect the cochlear and vestibular systems; cisplatin has a cochleotoxic effect (see Sect. 14.9).
Noise exposure: the threshold pattern results in a notch-type audiogram configuration. Initially temporary threshold shifts are observed. With repeated exposure the threshold shift can progress to permanent noise-induced hearing loss in the high frequencies. Loud sounds often occur in modern music machines used with ear phones, in different toys and in explosives (pyrotechnics).
Head injury: a dull head injury can lead to isolated damage of the inner ear (cochlear labyrinthine concussion) or damage of the otolith organ due to a bone conduction pressure. A typical sign is a high-frequency sensorineural hearing loss in form of a c5-dip (Brusis 2011) (at frequency 4000 Hz). In case of a unilateral skull base fracture, a contralateral labyrinthine concussion is also possible. Many cases also show an accompanying tinnitus.
15.1.4 Combined Sensorineural and Conductive Hearing Loss
Mixed hearing loss occurs when an individual has a conductive hearing loss overlying a sensorineural hearing loss. The air conduction threshold exceeds the bone conduction threshold by more than 10 dB, and the bone conduction thresholds are outside the normal range. With a mixed hearing loss, abnormalities are identified in the outer or middle ear as well as the inner ear. Mixed hearing loss varies in degree. In some cases, the conductive component of the mixed hearing loss can be medically or surgically treated. Ventilation tubes are especially helpful in infants with otitis media with effusion and a permanent sensorineural hearing loss.
15.1.5 Auditory Neuropathy/Auditory Dyssynchrony/Auditory Neuropathy Spectrum Disorder
In rare instances, a sensorineural hearing loss can be neural, i.e. the deficit is at the level of the auditory nerve. These types typically are labelled as auditory neuropathy (AN), auditory dyssynchrony (AD) or auditory neuropathy spectrum disorder (ANSD). In addition, children who have an auditory neuropathy generally do not respond well to traditional forms of audiological management, such as hearing aids. Preliminary case reports indicate positive outcomes with cochlear implants if the damage is located perisynaptically. Auditory neuropathy can be congenital or acquired.
Since the introduction of newborn hearing screening, there has been increasing recognition of children who present with normal outer hair cell (sensory) function but absent or abnormal auditory nerve function. Thus, when screened with otoacoustic emissions (OAEs), these babies will show a clear response on newborn hearing screening, because their outer hair cells are initially functioning but lack waves in the auditory brainstem response (ABR) (Gregg et al. 2004; Walker et al. 2016). Round window electrocochleography (RWECochG) and electric auditory brainstem responses (EABR) may be useful tools that will help with deciding on management (e. g. Cochlea Implantation) (Gibson and Sanli 2007) but are restricted to specialised audiologists and need a high degree of compliance. Aetiologically, this is a very heterogeneous group of children who have a variety of clinical histories and no single identifiable pathology (see below). This group of children can present with impaired speech perception and have difficulty with processing rapidly changing acoustic signals. The audiometric thresholds may range from mild to severe to profound hearing loss patterns. It has recently been suggested that this group should be described as having an auditory neuropathy spectrum disorder. The true prevalence of auditory neuropathy is unknown, and it is estimated that about 10% of all infants with hearing disorders show symptoms of ANSD.
Genetic conditions: non-syndromic, such as mutations in the otoferlin (OTOF) gene or pejvakin gene (PJVK). Syndromic, such as hereditary motor and sensory neuropathies (e.g. Charcot-Marie-Tooth), Friedreich ataxia, Mohr-Tranebjaerg syndrome, some mitochondrial mutations or other generalised neuropathies
Aplasia or hypoplasia of the vestibulocochlear nerve
Perinatal events: hyperbilirubinaemia, hypoxia, extremely low birth weight, complicated perinatal course
15.1.6 Central Hearing Disorders
Central hearing disorders are a consequence of a disruption in processing at varying levels of the hearing pathway, from the auditory nerve to inferior colliculus to the auditory cortex. They often present in a similar way as problems in auditory pathway development and can be manifested in a huge variety of ways that usually do not affect peripheral hearing or exhibit discrepancies between peripheral hearing and speech discrimination or other auditory functions, such as noise localisation, suppression of disturbing noise, binaural hearing or auditory memory. Children with central auditory disorders mostly present as easily distractible, having difficulties in remembering orally given tasks or to understand speech in noisy backgrounds. However, even more differentiated tasks, such as music perception, differentiation of pitch levels and recognition of emotional prosody or animal sounds can be affected (Peretz et al. 2001; Taniwaki et al. 2000; Griffiths et al. 1997; Yuvaraj et al. 2015; Bisiach et al. 1984; Hattiangadi et al. 2005). Generally, clinical differentiation from behavioural problems such as hyperactivity, learning disorders, attentiveness disorders or memory problems can be challenging. Specific testing of central auditory functions, and often psychological or developmental testing, is needed for differentiation, and an audiological follow-up is essential.
If a discrepancy between a pure-tone audiogram and a speech audiogram with or without background noise appears, more diagnostic steps have to be taken to assess central hearing. When a newly appearing central hearing disorder is suspected, cranial imaging with magnetic resonance tomography or computed tomography should be considered. For audiological diagnosis, measures of acoustically evoked potentials are crucial, if possible auditory brainstem responses, middle latency response and cortical evoked response audiometry, to detect disturbances of all parts of the auditory pathway. The diagnosis is completed by measuring OAE, contralateral OAE suppression, stapedius reflexes and acoustic reflex decay.
Central hearing disorders can be the first symptom of a beginning central pathology. As an example, this was the case in a 9-year-old boy who presented first with a subjective unilateral hearing loss without vertigo or tinnitus but had a normal pure-tone audiogram. When the hearing loss got subjectively worse, further pedaudiological testing was performed, showing reduced hearing in background noise, so an auditory processing disorder was suspected. After 6 more months of waiting, he developed a unilateral slight sensorineural hearing loss and following this was diagnosed with a benign brainstem tumour of the cerebellopontine angle after the course of 2 years of diagnosis. In the literature, a similar case of word deafness due to compression of the inferior colliculus has been described as being reversible after radiation (Joswig et al. 2015).
A very common reason for neural hearing loss is a benign tumour of the inner ear canal, such as acoustic neurinomas, in children most commonly neurinomas in neurofibromatosis or meningiomas, mostly presenting with unilateral hearing loss, tinnitus and vertigo. In most acoustic neurinomas, latencies of early brainstem potentials are prolonged or lacking (Selters and Brackmann 1977; Hoth 1991), OAE can be present or absent, depending on whether the inner ear is affected. Central hearing disorders can also be due to central inflammatory or vascular processes, tumours, trauma or other brain lesions, as well as neurodegenerative diseases, asphyxia during birth and other reasons, and grades of possible reversibility differ (Griffiths et al. 1997; Yuvaraj et al. 2015; Bisiach et al. 1984; Hattiangadi et al. 2005; Kihara et al. 2012; Zhu et al. 2010; Tabuchi et al. 2007; Iizuka et al. 2007; Hoistad and Hain 2003; Wakabayashi et al. 1999). In the case of central hyperbilirubinaemia, severity can range from slight reversible hearing loss to deafness (Nickisch et al. 2009). Auditory agnosia describes cases in which patients show clinical deafness in spite of normal or slightly reduced peripheral hearing, for example, after stroke, inflammatory processes or trauma, mostly in bilateral temporal lobes (Hattiangadi et al. 2005; Mendez 2001; Kaga et al. 2000a, b, 2003, 2015; Brody et al. 2013).
15.1.7 Progressive, Fluctuating and Sudden Hearing Loss
The clinical presentation of immune-mediated inner-ear disorders is very variable. The symptom most commonly associated with immune-mediated inner-ear disorders is a progressive or fluctuating sensorineural hearing loss (Agrup 2008). This is partially because auditory symptoms are the most studied inner-ear symptom, whereas vestibular symptoms can be overlooked, even though the two symptoms often develop together. Progressive hearing loss of late-onset type is typical in eye disorders, nervous system disorders and endocrine or metabolic diseases. Fluctuating patterns are common with immune-mediated inner-ear disorders (Gregg et al. 2004). However, sudden hearing loss or sudden vestibular loss also occurs. High-frequency hearing loss has been associated with patho-aetiological mechanisms involving vasculitis.
Sudden sensorineural hearing loss appears to be less frequent in the paediatric population than in adults. The definition of sudden hearing loss is a unilateral or bilateral hearing loss of 30 dB or more in three contiguous frequencies developing within a period of a few days. Several possible patho-aetiologies have been suggested with isolated sudden sensorineural hearing loss including viral/bacterial infections and vascular disorders. Hearing loss, especially when unilateral, may be missed in children because younger children are unable to express the complaint or parents are unable to recognise the loss of function. A progressive sensorineural hearing loss is present in 2–6% of all hearing-impaired children aged 8–13 years (Parving 1988). Progression in hearing loss is most frequent in early childhood and was found in more than 40% of participants in a study with 688 patients in the first years of infancy/childhood. Only 6% of children have progression defined as >15 dB for the averaged thresholds 0.5–4 kHz at age exceeding 4 years. The higher frequencies 2 and 4 kHz seem to be the most vulnerable (Johansen et al. 2004).
The cause of a hearing loss often remains unknown. Because of progression or fluctuation, the need for frequent surveillance of the hearing loss in infants and children before school age and repeated testing seems mandatory (Joint Committee on Infant Hearing 2000; Muse et al. 2013).
15.2 Auditory Processing Disorders
Definition and History
There are many definitions of auditory processing disorder (APD; Vermiglio 2014), but ‘listening difficulty despite normal auditory sensitivity’ is a simple and mostly inclusive one. ‘Listening’ is the process by which people actively engage with their auditory environment. It is synonymous with ‘auditory perception’ and includes both the sensory and cognitive aspects of hearing. Although the primary functional consequence of APD is difficulty in hearing speech, especially in challenging auditory environments, APD has historically been distinguished from a primary language or intellectual impairment. The importance of auditory perception, distinct from auditory sensitivity, was first recognised more than 60 years ago (Jerger 2009), although the interchangeable terms ‘APD’ and ‘central APD’ (CAPD; AAA 2010) are more recent (Keith 1977; Willeford 1974). APD may be ‘developmental’ (in children), ‘acquired’ (stroke, trauma or ageing brain) or ‘secondary’ to hearing loss (BSA 2011; Moore et al. 2013).
Demographics
APD is diagnosed primarily in children (7–17 years old) of both sexes, but adults of any age (Humes et al. 2012) and younger children are also affected (Emanuel et al. 2011; Lucker 2012). Among children, boys are more commonly referred and diagnosed than girls. Retention of developmental APD into adulthood has recently been found (Del Zoppo et al. 2015). Prevalence among the general population is not known with any precision, but rationalised estimates from one service suggested 0.5–1.0% (Hind et al. 2011). In three studies, 22% (Moore and Hunter 2013), 34% (Tomlin et al. 2015) and 46% (Ludwig et al. 2014) of children with normal auditory sensitivity referred to audiology were diagnosed with APD.
Mechanisms
The ‘real’ auditory system
Pathology in the cochlea (Moser et al. 2013). SGN spiral ganglion neuron, IHC inner hair cell, OHC outer hair cells. Image copyright and with permission from Wolters Kluwer Health, Inc.
Identification and Referral
Speech and language delays and inconsistent responses to sounds are often the first signs to caregivers that a young child may need help. Cross-referrals between community nurses, speech-language professionals and audiologists are common through the pre-school years (UK study; Hind et al. 2011). For older children, poor progress in school may be found, and family doctors, nurses and paediatricians often refer these cases. A US survey (Emanuel et al. 2011) found that audiologists measured pure-tone thresholds (100%), tympanometry (97%), speech recognition in quiet (92%), acoustic reflexes (69%), otoacoustic emissions (58%) and words in noise (54%) upon referral. Questionnaires were also usually given to parents or teachers. Referred children and adults with normal audiology nevertheless reported a variety of difficulties, including speech recognition and discrimination in challenging environments, spatial hearing, music/song perception and reproduction as well as auditory attention and memory. Children additionally can have delayed auditory and academic developmental milestones (Campbell et al. 2012).
Diagnosis
There is no universally agreed diagnostic procedure for APD. For example, in Germany APD is called ‘auditory processing and perception disorder’ (APPD) (German: auditive Verarbeitungs- und Wahrnehmungsstörung (AVWS)) to include impaired short-term memory and attention that are primarily in the auditory domain, as well as phoneme listening and the range of auditory perceptual problems recognised by ASHA (2005). In each case, APPD is diagnosed with the appropriate qualifier by using a multidisciplinary approach (GSPPA 2014). In one study, deficits in three such audiological tests resulted in a diagnosis of APD (Ludwig et al. 2014). In a multicentre UK study, performance below the recommended clinical cut-off on one or more subtests of the SCAN-C (Keith 2000), which is widely used as a screening test for auditory processing disorders, plus failure in one or more additional tests (random gaps, pitch pattern, duration pattern) was used (Dawes et al. 2009; Emanuel et al. 2011; Moore and Hunter 2013).
Intervention
Three management strategies (environmental, remediation, compensatory) were examined in a survey of nearly 200 US audiology services (Emanuel et al. 2011). Environmental modification was delivered by almost all services polled and included preferential seating, directing attention and wireless listening devices (e.g. Bluetooth). ‘Remediation’ was used by the majority of services, which consisted of training exercises, either computer-delivered or conventional. Compensatory strategies, including listening and metamemory, were also widely used. There is now considerable, high-quality evidence for the efficacy of wireless devices to improve listening, both during and following use of the devices (Hornickel et al. 2012; Keith and Purdy 2014). Computer-based training has received both positive (Kraus 2012; Moore et al. 2005) and negative (Stanford Center on Longevity 2014; Halliday et al. 2012) reviews, but in general, training benefit currently appears to be limited to skills closely related to those trained. Simple advice is low-cost and may be efficacious if actively promoted, but limited training and compliance monitoring have precluded critical evaluation.
Summary
APD is currently diagnosed following reports of listening difficulties, normal audiometry and poor performance in additional tests of auditory and cognitive function. Listening difficulties may derive either from top-down cognitive processing or control dysfunction or from suprathreshold sensory temporal processing dysfunction in the cochlea or brainstem. The most effective treatment strategies appear to be advice on listening and use of a communication device.
15.3 Hyperacusis
15.3.1 Definition and Epidemiology
Hyperacusis is a symptom defined as an
experience of inordinate loudness of sound that most people tolerate well, associated with a component of distress… this experience has a physiologic basis… but it also has a psychological component.
Baguley and Andersson (2007)
Other related terms include phonophobia, which literally means fear of sound but is often used clinically to describe an aversion to sound in general (e.g. in migraine); misophonia, which means dislike of particular soft sounds (e.g. the sound of somebody chewing); and decreased sound tolerance to refer to any of the above (Hall 2013). Loudness recruitment, in which a small increase in sound intensity is perceived as a large increase (as is typically found in sensorineural hearing loss), should not be confused with hyperacusis. There is a lack of clarity and consistency in the definitions and terminology used in the literature, so such distinctions are important to note.
Hyperacusis is reported to affect 9–16% of the general population (Andersson et al. 2002; Skarzyński et al. 2000) and is severe in 2% (Baguley and McFerran 2011). It is closely associated with tinnitus: hyperacusis is reported in 40% of patients whose primary concern is tinnitus (Jastreboff et al. 1996), and tinnitus is reported in 86% of those whose primary concern is hyperacusis (Anari et al. 1999).
15.3.2 Mechanisms
Various peripheral and central mechanisms for hyperacusis have been proposed. These mechanisms may combine to different degrees in different patients.
Stapedial reflex dysfunction is one such potential peripheral mechanism. This proposal originated in the observation that decreased sound sensitivity is a common symptom of several conditions with accompanying facial palsy (e.g. Bell’s palsy) or stapedial muscle dysfunction (e.g. following stapedectomy) (Baguley and McFerran 2011). Dysfunction of the medial or lateral efferent auditory systems, which innervate the outer and inner hair cells (OHCs/IHCs) of the cochlea, respectively, has also been proposed (e.g. Herráiz and Diges 2011): disinhibition of the OHCs or increased glutamate release at the base of the IHCs may lead to constant overstimulation of the IHCs.
Given the high rates of various forms of loudness intolerance reported in disorders known to be influenced by serotonin dysregulation (such as Williams syndrome, depression, migraine and post-traumatic stress disorder), it is believed that serotonin may play a significant role. There is, however, some dispute about whether true hyperacusis is found in these latter cases or whether it is in fact a general intolerance of sound, in which case other mechanisms may be involved (e.g. Blomberg et al. 2006).
Change in central auditory gain is a normal consequence of change in the peripheral auditory system, but where dysregulated it may be a significant factor in hyperacusis. For example, Formby et al. (2003) demonstrated in normal-hearing listeners that auditory deprivation by means of earplugs worn continuously for 2 weeks leads to increased central auditory gain, observed as hearing threshold shifts on pure-tone audiometry and on loudness scaling measures once the earplugs have been removed. The reverse, 2 weeks of constant low-level noise through in-the-ear wearable devices, leads to decreased central auditory gain (i.e. decreased loudness perception and increased sound tolerance). Sun et al. (2012) demonstrated in rats that the sensory deafferentation that follows cochlear hearing loss induced by noise exposure also leads to an increase in central auditory gain. These and other studies imply that central auditory gain is adaptable and can be affected by changes in levels of peripheral auditory stimulation, that such change affects loudness judgements and that dysregulated central auditory gain may therefore play a significant role in the pathophysiology of hyperacusis. Sun et al. (2014) proposed that even temporary hearing loss at an early age may affect tolerance of sound during development.
Involvement of the amygdala, limbic and autonomic systems, perhaps triggered by this abnormal auditory gain, has also been postulated (e.g. Jastreboff and Hazell 1993; Herráiz et al. 2006). Activation of these systems in association with sound gives rise to emotional responses such as anxiety, fear and depression. Baguley and Andersson (2007) have developed a fear-avoidance model of hyperacusis, in which fear of the experience of loud sound leads to increased awareness of the presence of sound and more frequent (unconscious) avoidance activities and possibly phobic reactions.
One limitation of the above-described mechanisms is that many patients with hyperacusis do not have abnormal peripheral function (Baguley and McFerran 2011), so any alteration in central auditory gain may be modulated by other factors.
15.3.3 Assessment
Hyperacusis is a subjective symptom, and no objective diagnostic assessment is currently possible. Diagnosis is based chiefly on the symptom report. The following assessment methods do, however, provide useful information to help exclude underlying pathology and enable successful, individually tailored treatment and counselling steps.
Baguley and Andersson (2007) proposed that an appropriate clinical history should include asking the patient or their parent/carer about their sound sensitivity (onset, development over time, types of sounds, reaction), its impact on their life, avoidance activities (including the use of hearing protection), other diagnoses (e.g. depression, migraine or Williams syndrome) and other sensory sensitivities. A clinical examination of the ears and cranial nerve function is also recommended.
Audiometric Assessment
Audiometric assessment is essential but should be undertaken with a level of caution, bearing in mind the risk of triggering or exacerbating the very problem for which the patient is seeking help. Hall (2013) recommends reminding the patient that they can stop the tests at any time. Pure-tone audiometry (including the extended high-frequency range) and tympanometry are beneficial in order to identify any underlying hearing loss. Presentation of the initial audiometric stimuli at a lower level than usual may help avoid triggering the patient’s symptoms. Uncomfortable loudness level (ULL) testing, which measures the level at which a sound becomes uncomfortably loud, is often performed in order to investigate the severity of the problem and provide a baseline against which therapeutic benefit can be measured. Categorical loudness scaling tests such as Würzburger Hörfeld (Goebel and Günther 2014) or Oldenburger Hörfeld (Lehnhardt and Laszig 2009) can deliver even more detailed information than ULL testing (see Sect. 4.3.3 for further detail (pure-tone audiometry)).
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