Pre-existing autism in paediatric ENT

First described by Kanner in 1943,^{Reference Masi, DeMayo, Glozier and Guastella21} autism spectrum disorder has gone through various stages of recognition until the latest by the National Institute for Health and Care Excellence in 2013.²² With the rising incidence of autism spectrum disorder diagnoses, and with studies consistently demonstrating an estimated 40 per cent or more of diagnosed children showing symptoms of sound sensitivity,^{Reference Rimland and Edelson8} it is key for otolaryngologists and audiologists to recognise the condition.

Autistic children have also been shown to exhibit a higher prevalence of anxiety, which can be particularly challenging in healthcare settings.^{Reference Benich, Thakur, Schubart and Carr12} Sensory symptoms can become a serious challenge for autistic children and their carers.^{Reference Fahy, Corbett and Keogh2} A study by Fahy et al., in a paediatric ENT setting, concluded that healthcare professionals considered parents to be the ‘experts’ when it came to managing and understanding their autistic children's needs.^{Reference Fahy, Corbett and Keogh2}

Autism and auditory symptoms

A paper by Law et al.^{Reference Law, Rubenstein, Marvin, Toroney and Lipkin23} found that the lifetime prevalence of auditory sensory issues (tinnitus, hyperacusis, misophonia and phonophobia) may be as high as 86.6 per cent in autistic populations.

Hyperacusis is common in autistic populations,^{Reference Danesh, Howery, Aazh, Kaf and Eshraghi10} and can affect individuals in different ways, from causing anxiety to loss of sleep and trouble concentrating.^{Reference Danesh, Howery, Aazh, Kaf and Eshraghi10} There are numerous papers theorising the aetiology of hyperacusis in autism spectrum disorder, from increased neural synchrony^{Reference Danesh, Howery, Aazh, Kaf and Eshraghi10} to a small or absent superior olivary complex.^{Reference Bennetto, Keith, Allen and Luebke24} Despite the evidently high prevalence of hyperacusis in autism spectrum disorder patients, the link remains poorly understood.^{Reference Williams, Suzman and Woynaroski25} Studies conclude that the prevalence of hyperacusis in autistic children is generally around 40 per cent^{Reference Wilson, Sadler, Hancock, Guinan and Lichtenhan26} (range, 29–69 per cent^{Reference Hitoglou, Ververi, Antoniadis and Zafeiriou4,Reference Danesh, Howery, Aazh, Kaf and Eshraghi10,Reference Wilson, Sadler, Hancock, Guinan and Lichtenhan26,Reference Williams, He, Cascio and Woynaroski27} ), with a lifetime prevalence of decreased sound tolerance in autism spectrum disorder individuals of 70–86.6 per cent.^{Reference Williams, Abdelmessih, Key and Woynaroski9,Reference Williams, He, Cascio and Woynaroski27} The general population incidence of hyperacusis is between 3.2 per cent and 17.1 per cent.^{Reference Danesh, Howery, Aazh, Kaf and Eshraghi10} One study found that, of 61 children with a diagnosis of ‘troublesome hyperacusis’, autism was subsequently recognised in 13 per cent,^{Reference Myne and Kennedy28} which is higher than the current national average of around 1.9 per cent.^{Reference Fahy, Corbett and Keogh2,Reference Mathew, Bryan, Chaudhry, Chaudhry, Kuhn and Tysome3}

Scheerer et al.^{Reference Scheerer, Boucher, Bahmei, Iarocci, Arzanpour and Birmingham29} discussed how hyperacusis in autistic children can be associated with multisensory integration. This may be due to sensory modulation differences, with the brain becoming overwhelmed, and unable to filter and process the intensity of the auditory stimulus.^{Reference Scheerer, Boucher, Bahmei, Iarocci, Arzanpour and Birmingham29} This correlates with the recognised autistic trait of becoming overwhelmed in busy places.^{Reference Danesh, Howery, Aazh, Kaf and Eshraghi10} It has been demonstrated that a majority of autistic children (59 per cent in a survey by Wilson et al.^{Reference Wilson, Sadler, Hancock, Guinan and Lichtenhan26}) are startled by loud noises, in comparison to 15 per cent of neurotypical counterparts.^{Reference Scheerer, Boucher, Bahmei, Iarocci, Arzanpour and Birmingham29} Hyperacusis can lead to maladaptation in social and academic situations for autistic children, where avoidance and isolation can worsen social skills and anxiety, and create difficulties with school work carried out in a loud environment.^{Reference Wilson, Sadler, Hancock, Guinan and Lichtenhan26}

Tinnitus, an audiological problem that causes an individual to hear sounds without the presence of an external auditory stimulus,^{Reference Esmaili and Renton30} is estimated to have a lifetime prevalence of 10–15 per cent in the general population.^{Reference Danesh, Lang, Kaf, Andreassen, Scott and Eshraghi31} A survey of autistic children demonstrated that 35 per cent experienced tinnitus, with about half experiencing it in both ears.^{Reference Danesh, Lang, Kaf, Andreassen, Scott and Eshraghi31} That survey used the Tinnitus Reaction Questionnaire, which assesses the associated psychological distress caused by tinnitus.^{Reference Danesh, Lang, Kaf, Andreassen, Scott and Eshraghi31} The average Tinnitus Reaction Questionnaire score among autistic people with tinnitus was 27 (formal treatment is recommended for a score higher than 17), demonstrating a significant issue.^{Reference Danesh, Lang, Kaf, Andreassen, Scott and Eshraghi31} Interestingly, in that study, 11 per cent of patients reported tinnitus even in the presence of background noise, which is not a classic feature of tinnitus.^{Reference Danesh, Lang, Kaf, Andreassen, Scott and Eshraghi31}

Autism and auditory processing

Abnormal auditory processing in autism spectrum disorder has been previously proposed, though no definitive explanation has been identified.^{Reference O'Connor32} Bouvet et al.^{Reference Bouvet, Simard-Meilleur, Paignon, Mottron and Donnadieu33} considered that autistic people have more sensitive hearing, and are therefore able to detect changes in musical notes and pitch more easily than their neurotypical counterparts.^{Reference Bouvet, Simard-Meilleur, Paignon, Mottron and Donnadieu33} This pattern of cortical processing is thought to influence vision as well as interests, allowing autistic people to hyperfocus on tasks and hobbies, a well-documented autistic trait.^{Reference Bouvet, Simard-Meilleur, Paignon, Mottron and Donnadieu33,Reference Remington and Fairnie34}

A problem that autistic people often face is trouble hearing and understanding speech in the presence of background noise. This could be due to concurrent hearing problems, but might also be a result of the functioning aspect of the autistic mind. ‘Failure of selective attention’ is well documented in the autism literature, and can often be due to sensory overload.^{Reference Alcántara, Weisblatt, Moore and Bolton35} Alcántara et al.^{Reference Alcántara, Weisblatt, Moore and Bolton35} referred to ‘auditory scene analysis’ where, in the autistic mind, different auditory inputs are often grouped internally into different auditory ‘objects’. Consequently, it becomes difficult for the mind to focus on just one of these auditory inputs.^{Reference Alcántara, Weisblatt, Moore and Bolton35} This can become distressing for an autistic child, particularly within a loud classroom environment, putting them at an educational disadvantage.^{Reference Alcántara, Weisblatt, Moore and Bolton35}

A paper by Remington and Fairnie^{Reference Remington and Fairnie34} attempted to contextualise hyperacusis with neural pathways, proposing that autistic people have an ‘increased perceptual capacity relative to neurotypical individuals’, allowing autistic people to be able to process information to a higher degree, making it easier to become overwhelmed.^{Reference Remington and Fairnie34} This would coincide with a paper by Myne et al.,^{Reference Myne and Kennedy28} where autistic people were reported to have a higher acuity for musical notes. Myne et al. discussed M100 (auditory evoked response) latency delays in autistic children being largely in the right hemisphere, which commonly processes sound and music.^{Reference Myne and Kennedy28} These authors found that around 10 per cent of autistic children experienced right-sided hemisphere 10 ms M100 latencies compared with neurotypical controls.^{Reference Myne and Kennedy28} M100 latency delays can be indicative of a disruption in the pathway encoding simple sensory information.^{Reference Port, Edgar, Ku, Bloy, Murray and Blaskey36} A paper by Matsuzaki et al.^{Reference Matsuzaki, Ku, Berman, Blaskey, Bloy and Chen37} also supports the theory of right-sided hemisphere bias in autistic people. These authors used magnetoencephalography to attempt to measure the neurophysiological mechanisms used for auditory language discrimination. They demonstrated auditory mismatch field amplitudes and latencies, largely in the right hemisphere.^{Reference Matsuzaki, Ku, Berman, Blaskey, Bloy and Chen37} The significantly increased rightward mismatch field amplitude lateralisation they noted in autistic adults is consistent with the paper by Myne et al.,^{Reference Myne and Kennedy28} as well as other papers reporting structural and functional abnormal hemispheric asymmetry in paediatric autism spectrum disorder. This indicates a differential path of maturation in the cortical auditory systems in autistic children.^{Reference Matsuzaki, Ku, Berman, Blaskey, Bloy and Chen37}

Autism and hearing loss

Hearing abnormalities, of both sensorineural and conductive origin, are estimated to be present in 33–46 per cent of autistic children.^{Reference Hitoglou, Ververi, Antoniadis and Zafeiriou4} The link between hearing loss and autism spectrum disorder, however, has sparse evidence to support it. Some studies estimate the hearing loss in autism spectrum disorder to be ten times higher than in the neurotypical population, with others documenting similar rates between autistic and neurotypical populations.^{Reference Mathew, Bryan, Chaudhry, Chaudhry, Kuhn and Tysome3}

Some of the stereotypical signs of autism, for example, toe walking, hand flapping or ‘sustained odd play’, can result in an earlier diagnosis. However, it has been shown that hearing impairment can delay the diagnosis of autism.^{Reference Mandell, Novak and Zubritsky38} A study by Mandell et al.^{Reference Mandell, Novak and Zubritsky38} included 382 autistic children and young adults aged under 21 years. The average age of autism diagnosis was 3.1 years. The authors demonstrated that if a child had hearing impairment, their average age at diagnosis was 4.1 years, and hearing impairment was the symptom most likely to delay diagnosis.^{Reference Mandell, Novak and Zubritsky38}

Identifying a true dual diagnosis of autism spectrum disorder and hearing loss can be challenging because of the nature of the symptoms of both conditions. Each condition complicates diagnosis of the other.^{Reference Meinzen-Derr, Wiley, Bishop, Manning-Courtney, Choo and Murray5} Both conditions independently cause delays in language development, and, when concurrent, this can worsen the problem, hence early identification is key.^{Reference Meinzen-Derr, Wiley, Bishop, Manning-Courtney, Choo and Murray5} Gillberg et al.^{Reference Gillberg, Ehlers, Schaumann, Jakobsson, Dahlgren and Lindblom39} proposed that if deafness is suspected under the age of three years, this should also be highly indicative of autism.^{Reference Schwemmle, Schwemmle and Ptok40}

Autism and cochlear implantation

Diagnosing a child with severe autism with profound sensorineural hearing loss can pose a challenge, specifically in determining whether the hearing test result is due to a true loss of hearing or communication differences associated with autism.^{Reference Valero, Sadadcharam, Henderson, Freeman, Lloyd and Green41}

In the twentieth century, it was generally thought that autistic children would not benefit from cochlear implantation, but in the past 20 years evidence has emerged suggesting that there is some benefit to be gained. A review article^{Reference Mathew, Bryan, Chaudhry, Chaudhry, Kuhn and Tysome3} showed that of nine studies analysed, eight demonstrated that autistic children had an overall improvement in their speech expression following cochlear implantation, although the extent of this benefit was highly variable. It was also concluded that, in general, non-compliance was usually related to the severity of autism spectrum disorder.^{Reference Mathew, Bryan, Chaudhry, Chaudhry, Kuhn and Tysome3}

There is a move towards cochlear implantation at around the age of 12 months. Autism spectrum disorder diagnoses are usually made after the age of three years, and hearing problems in autism spectrum disorder are prevalent. It is therefore essential for the otolaryngologists and audiologists to whom children present with a profound hearing loss to be aware of the potential for a concurrent autism spectrum disorder diagnosis.^{Reference Mathew, Bryan, Chaudhry, Chaudhry, Kuhn and Tysome3}