Hyperacusis in children: a scoping review

Hyperacusis is a chronic condition commonly defined as a lowered tolerance or increased sensitivity to everyday environmental sounds [1, 2]. It can cause significant impairment to a person’s normal functioning. Conditions such misophonia and phonophobia also involve decreased sound tolerance and can be co-existing with hyperacusis, evoking similar reactions and potentially involving the same brain areas of emotion and fear [3, 4]. That said, there is no definitive evidence as to the aetiology and diagnosis of hyperacusis as yet, therefore differentiating it from these conditions is debatable. According to the evidence to date, phonophobia may differ from hyperacusis in that it is a psychiatric condition, diagnosable under the DSM-IV classification for specific phobias [5] and which involves fear from the troublesome sound(s). Misophonia has been commonly associated with difficult to control bursts of anger and sometimes rage when exposed to specific human oral and nasal sounds [6, 7]. Hyperacusis is also distinct from recruitment, which involves a narrowing of the auditory dynamic range due to hearing loss [8]. Instead, people with hyperacusis tend to experience intense discomfort or pain due to certain sounds of various loudness levels - from hushed sounds such as distant traffic or the sound of a refrigerator motor, to loud sounds such as hand dryers or electric food mixers. Patients would perceive these sounds as much louder or intense than they actually are [9]. Thus, patients can either have normal uncomfortable loudness levels (ULLs), except for specific troublesome sounds, or have generally reduced ULLs, irrespective of the type of sound they are exposed to [10]. People with hyperacusis also exhibit normal hearing (for their age) or slight hearing loss on pure tone audiograms, and reportedly 86% experience tinnitus [11, 12]. Hyperacusis can occur in otherwise healthy individuals [13] but is generally associated with a number of pathologies, including closed head trauma [14], depression [15], and post-traumatic stress [16]. Hyperacusis is also a complaint in approximately 95% of people with William’s Syndrome (WS), and 63% of people with autism spectrum disorders (ASD) [17, 18]. It has also been linked to Asperger’s Syndrome (AS) [19], though AS falls under the umbrella diagnosis of ASD. The high incidence of hyperacusis in developmental disorders has led to hyperacusis being viewed as a typically paediatric disorder [10, 20], although it also occurs in children with no other health concerns. Evidence on the prevalence of hyperacusis in children is sparse and inconclusive. A recent systematic review by Rosing et al. [21] documented that this can vary between 3.2 and 17.1%, the variability likely a product of how the prevalence questions were posed in different studies. However, hyperacusis is clearly a significant clinical concern in children. The British Society of Audiology (BSA) clinical practice guidance for tinnitus in children [22] highlights the importance of identifying whether the child has any intolerance of loud sounds, and managing this appropriately. However, no clinical guidelines specifically for hyperacusis in children have yet been developed [23]. A review is therefore indicated to consider the profile of children with hyperacusis and the priorities for future research.

Due to the broad, explorative nature of our research questions in this emerging field of evidence, a scoping review was determined to be the most suitable methodology. Unlike the systematic review which aims to answer specific questions in a rigorous manner, the scoping review is designed to allow the mapping of key concepts that underpin a research topic [24], which, in this case was the clinical profile of children with hyperacusis. Hence a methodological framework for scoping reviews was followed [24‐27] involving six stages whereby (1) the purpose and research questions were defined, (2) relevant studies were identified using a three-step literature search to balance breadth and comprehensiveness, (3) studies were selected using an iterative team approach, (4) data were charted, (5) results were collated, summarised and reported, including the implications for policy, practice, or research, and (6) findings were reviewed by clinical experts in the field who did not take part in stages 1–5. This scoping review does not include a previously published protocol.

Figure 1 displays the flow of records identified, screened, included or excluded, and reasons for exclusion. We identified 744 records through database searching and seven from hand searching. After removing duplicates, we were left with 351 records, which were screened at a title and abstract level. Of these, 55 were selected for full text screening, following which, 34 were excluded and 21 records were deemed eligible for the review (see Table 1).

The 21 included records were published between 1994 and 2020, and over half of them were case studies. Information on the type of care provider was included in ten records, four being Ear Nose and Throat (ENT) clinics [28‐31], including one which specialised in paediatrics [24], and one Educational Psychological Advisory (EPA) service for children [31]. The rest included a Tinnitus and Hyperacusis Therapy Specialist Clinic [32], paediatric audiology [33], one tinnitus clinic [34], one neurology clinic [35], and two psychiatry clinics [36, 37], of which one [36] specialised in children and adolescents.

Specific complaints were reported in all 21 records. Although all records focused on hyperacusis, the term hyperacusis was used to describe the complaint in nine of those [21, 28, 33, 34, 38‐42]. Other records used patient-specific complaints which feature in common definitions of hyperacusis. These include auditory hypersensitivity [36, 43], hypersensitivity to sound [35], ‘very sensitive’ and ‘oversensitive’ to sound [20, 37], ‘bothered and annoyed by sounds’ [44], ‘distress in response to ordinary sounds’ [29], ‘pain and intolerance of loud sounds’ [30], ‘pain and fear in response to sound’ in case 2 [2], ‘difficulty tolerating noise at school [2], and ‘sound intolerance’ [32, 45] (Table 1).

This scoping review aimed to catalogue the literature providing a clinical profile of children experiencing hyperacusis, and how they have been assessed and treated. Only 21 relevant records were identified, indicating a paucity of research in this field. We mapped the available evidence on the children’s clinical profile of hyperacusis in terms of age and gender, comorbid conditions, LDLs, troublesome sounds, physical sensations, reactions, coping behaviours, and areas of impairment in daily living. Relevant assessment and treatment methods used with children with hyperacusis were also catalogued.

Age at time of hyperacusis onset was not reported in the records we reviewed, however one study which involved a large sample indicated that all children had a gradual onset [28]. In terms of age at presentation, we found that a few of the case studies reported on 5- and 11- year-olds. However, studies with larger samples reported that the commonest age at presentation as 3 to 4 years old [33, 55]. In clinical practice, hyperacusis in children between 3 and 4 years old is considered to occur as part of normal auditory development, which is likely to settle by itself with the maturation of the central auditory system [56, 57].

In terms of gender, the majority of the case studies we reviewed described male children. Although this does not signify that hyperacusis is more prevalent in males - studies with larger samples have reported a male majority [28, 33, 55]. This could be due to the type of research population selected in those studies. ASD for example, where hyperacusis is a common complaint, is more common in males. On the other hand, Ralli et al. [46] observed a majority of male children in their sample and this difference was found to be statistically significant. More research is needed to clarify the potential gender effect.

As already noted, hyperacusis is often a symptom in ASD [18] and indeed, we found that ASD was one of the two most commonly reported comorbid conditions of hyperacusis. Tinnitus was just as common in children with hyperacusis, followed by WS and ADHD. Epilepsy and hearing loss were also commonly reported. Across the records we reviewed the proportion of children who experienced primary hyperacusis, in isolation of other health conditions, was smaller. Of these children, some have experienced glue ear, which can increase the perception of loudness once it has resolved [33]. This highlights the question whether hyperacusis is a symptom or a disease in itself, to be addressed by future aetiology research, not only of hyperacusis, but also ASD, WS and tinnitus, and their association.

Although natural variety exists [3], patients with hyperacusis are generally presumed to have lowered ULLs [20] and taking ULLs had become the traditional tool for diagnosing hyperacusis. Surprisingly however, the majority of records did not assess ULLs. The few that did, reported them in little detail. These findings reflect the recent suggestions that ULLs are not a reliable measure in adults or children [58, 59]. Further to this, measuring ULLs can also be distressing for young children and can undermine the building of rapport with the clinician [60]. This could be a consideration for standard ENT assessment for hyperacusis.

There was a variety of sounds reported by children as troublesome. From the data catalogued here it appears that hyperacusis is generally associated with ‘unnatural’ noise produced by machines, or with natural sounds, e.g. those produced by people or animals, that are simultaneously loud and sudden. It is worth noting that children are not bothered by such sounds if they are produced by themselves which implies that it is not just certain bothersome sounds that create a reaction but perhaps also the lack of control the child feels over them. Indeed Phillips and Carr 1998 [61] proposed that issues with sound perception may arise from both physical and psychological sources. Psychological or emotional factors in the hyperacusis reaction and their interplay with the physiological responses must be addressed in future research into the aetiology of hyperacusis.

It is also possible that patients with developmental disorders are more likely to be troubled by a particular type of sound than others with hyperacusis. Future research on the clinical profile of paediatric hyperacusis could provide clarification on the ways in which children with and without developmental disorders differ, and the characteristics of sounds that bother them. Such information would be useful to better define the symptomatology of paediatric hyperacusis as an independent condition rather than as being part of a condition or syndrome.

There is little literature on the physical sensation of hyperacusis, i.e. what makes the sound so uncomfortable. We found that where there were reports of physical sensation, those were of ‘pain’ in the ears, and in one case in the head. In another case, co-occurring nausea was also observed. The reasons for such physical sensations could be a consideration for research into the aetiology of hyperacusis.

Although the literature describes a wide variety of behavioural reactions, we found that most commonly children covered their ears, cried, or became aggressive. Aggression in children is a common expression of anxiety [62]. Older children were more likely to cope by avoiding the situations where they might be exposed to the sound, or wearing ear protection. Younger children were less likely to engage in coping behaviour; instead, their parents had put limitations on their usual activities to avoid their child becoming distressed. The biggest impact on family functioning was in terms of getting out of the house, attending social events, and school performance. The first two would limit social interactions with peers, and the normal life of the child’s family members causing tension in their relationships. All three factors can result in high levels of stress, low quality of life, and hinder progression in life for both child and family.

Unfortunately as this condition has emerged recently and has a poor evidence base concerning children, clinicians such as GPs, paediatricians, school nurses, psychologists, audiologists, educators, and health visitors, who encounter this condition, are unprepared to support such families. This originates in the current lack of child-specific assessment and treatment tools. None of the records used validated hyperacusis - specific assessment questionnaires that were standardised with a paediatric population. Semi-structured interviews were commonly used to diagnose and assess the severity of hyperacusis. However, there was notable variation in the types of questions the children or their parents were asked. A validated questionnaire standardised with a paediatric population is urgently required to assist in the early identification of children with significant hyperacusis and to support clinical research evaluating the effectiveness of interventions.

None of the records we identified sought to develop a treatment specifically tailored for children with hyperacusis and those that described treatments used for children had no previous empirical evidence of effectiveness. There was also a great variability in the treatments documented and in the different combinations used e.g. psychological treatment with medication or with sound therapy. However, none of the records provided a detailed description of its treatment components and none demonstrated significance in their patient outcomes. Randomised controlled trials are required to compare and assess the effectiveness of these treatments for children. Appropriate treatment and assessment could help identify and support such children both in school and at home. There has been positive development in the field of tinnitus where there is designated clinical guidance for managing children and potential adjustments in the classroom [22]. Future research could focus on adapting these for children with hyperacusis.

Some limitations of this review are noted. Although we used a wide range of synonyms of hyperacusis in our searches, there may have been relevant studies that have not been identified. In terms of the origin of the studies we reviewed, there was a dominance of records from western countries resulting in a potential bias of our findings. For instance, the clinical profile in other cultures may have different dominant features, which future research could explore. In addition to this, the majority of children that were described had some type of a developmental condition, which may have further biased the clinical profile we describe. The records obtained may also not represent the full clinical profile of hyperacusis due to the potential presence of the ‘file drawer effect’, where certain case studies, for example those with children without co-occurring conditions, were not published. A further limitation to this review is that it is limited to research published in the English language only. As a result, it is possible that our findings may present with cultural and ethnic bias. Specifically the clinical profile, assessment and treatments methods may differ in other countries. The relationship between hyperacusis in children and cultural factors would be interesting to assess in future research. Another limitation to this review is that there is no standardised diagnostic criteria for hyperacusis. For consistency we only included records that explicitly used the term hyperacusis, but the underpinning diagnostic criteria may differ across cases hence there may be instances of misdiagnosis.

This scoping review catalogued the existing research on the clinical profile of hyperacusis in children and the methods of assessment and treatment. The clinically relevant findings emerging from this review, which would need further verification in research, are the following: the commonest presentation age is 3 to 4 years old with a potential male dominance; ASD and tinnitus were the most common co-occurring conditions; the most common troublesome noises were household electrical appliances; the common reaction was to cover their ears, cry and aggressive behaviour. The commonest impact of hyperacusis was on family functioning, including getting out of the house and attending social events and on school performance. Semi-structured interviews and questionnaires were the most common assessment method. All four treatment options for hyperacusis in children – psychological, sound, medication, TRT and neuro-rehabilitation, were applied either alone or in combination and all showed notional improvement in severity.

This review aimed to bridge a gap in our understanding of the ways in which hyperacusis presents in children. The information we catalogued on various elements of clinical profile can serve as a stepping stone in specifying the symptoms of paediatric hyperacusis, and aid clinical diagnosis. It will also support future research to develop questionnaires for clinical measurement of the impact of hyperacusis on children, and the measurement of treatment related change in clinic and in trials.