Continuing Education Activity
Pediatric hearing loss is a broad category that covers a wide range of pathologies. Early detection and prompt management are essential, as the development of language and psychosocial skills are significantly influenced by pediatric hearing loss. Additionally, early detection may identify potentially reversible causes or other underlying problems that can be managed. This activity describes the diagnosis and therapeutic strategies for managing pediatric hearing loss and stresses the role of the interprofessional team in the care of children with hearing loss.
Objectives:
- Outline the types of pediatric hearing loss.
- Explain when pediatric hearing loss should be included in the differential diagnosis.
- Identify management options for pediatric hearing loss.
- Review an optimally functioning interprofessional team approach to coordinate care and enhance outcomes for pediatric patients with hearing loss.
Introduction
Pediatric hearing loss is a broad category that covers a wide range of pathologies. Early detection and prompt management are essential for the development of normal language and psychosocial functioning, as well as to identify potentially reversible causes or other underlying problems. Hearing is measured in decibels, and the severity of the hearing loss is graded by hearing thresholds. The normal hearing range is 0-20 decibels (dB) which equates to being able to perceive sound quieter than a whisper. Mild hearing loss corresponds to a range of 20-39 dB, moderate 40-69 dB, severe 70-89 dB, and profound is greater than 90 dB.
There are three main types of hearing loss; conductive, sensorineural, and mixed. The former typically occurs due to a problem transmitting sounds at the level of the external or middle ear. The major cause of conductive hearing loss in children is otitis media with effusion (glue ear). Sensorineural hearing loss results from a disruption of the auditory pathway at any point from the cochlea of the inner ear through to the brainstem, and despite being relatively uncommon in children as a whole, it is the primary cause of permanent hearing loss in the pediatric population. Mixed hearing loss occurs when there are both conductive and sensorineural components.
Etiology
Hearing loss can be broadly characterized as congenital or acquired in the pediatric population.
Congenital Causes
Congenital hearing loss can be classified as genetic and non-genetic in etiology. The former category is responsible for greater than half of congenital causes and can be due to either an autosomal dominant, recessive, or sex-linked mutation.[1] Genetic causes are often further subdivided into syndromic versus non-syndromic categories based on whether the patient suffers from an underlying genetic syndrome. Approximately 30% of the genetic causes of hearing loss are syndromic.[2] The most common cause of congenital hearing loss is autosomal recessive non-syndromic hearing loss.
TORCH organisms (toxoplasmosis, rubella, cytomegalovirus (CMV), and herpes) have been identified as key infective causative agents. CMV is the most common cause of congenital non-genetic hearing loss in the developed world. Other congenital causes include trauma, ototoxic medications used in the antenatal period, and several perinatal risk factors such as prematurity, low birth weight, and hyperbilirubinemia.
Acquired Hearing Loss
Otitis media with effusion is the number one cause of acquired hearing loss in children. It is beyond the scope of this article to cover this in detail, but it classically has a bimodal peak at 2 years and 5 years of age and is characterized by a conductive hearing loss associated with a flattened tympanogram.[3] It typically resolves without intervention as the eustachian tube matures or following the insertion of a ventilation tube in the middle ear.[4] Adenoidal hypertrophy can contribute to this clinical picture.[5] Infections also present another major category for acquired hearing loss, with a particularly strong link with bacterial meningitis, mumps, and measles. Other reasons include primary otological pathologies such as cholesteatoma, impacted wax, and otosclerosis, as well as trauma.
High-risk factors in neonates:
- Congenital infections
- Family history
- Craniofacial anomalies
- Hyperbilirubinemia
- Birth weight 1500 g
- Low Apgar
- Bacterial meningitis
- Need prolonged intubation
Epidemiology
Hearing loss occurs in 1-3 newborns per 1000 births,[6] with 1-2 per 1,000 suffering from permanent childhood hearing impairment.[7] There is a slightly increased prevalence of hearing loss in boys compared to girls, with a ratio of 1.16:1.0.[7] There are around 45,000 children with hearing loss in the UK, half of which are congenital in origin.[8]
Pathophysiology
Any condition that lowers the transmission of sound from the external space to the cochlea will cause conductive hearing loss. This includes cerumen, abnormalities of the helix or auricle, effusions, and fixed ossicular chain. Besides cholesteatoma, other masses include glomus tumors, schwannomas of the facial nerve, and hemangiomas.
Sensorineural hearing loss is due to interruption of sound transmission after the cochlea. This may be due to damage to the hair cells or damage to the 8th cranial nerve. Even mild distortions in the hair cells can result in severe hearing loss.
Categories of hearing loss are as follows:
- Slight hearing loss: 16-25 dB
- Mild hearing loss: 26-40 dB
- Moderate hearing loss: 41-55 dB
- Severe hearing loss: 71-90 dB
- Profound hearing loss: 90 dB
History and Physical
Hearing loss can present in different ways depending on the age of the child. Hearing loss in neonates is almost exclusively picked up via newborn screening program assessments. In older children, parents or other professionals, such as school teachers, may notice delayed language skills, behavioral problems, or listening to the television at raised volumes. In the history, it is important to ascertain whether there are any associated otological symptoms such as otorrhoea, otalgia, tinnitus, or vertigo. A thorough history is required, including asking about any other neurological symptoms, and medical history, including drug history and precipitating events such as trauma, recent viral infections, or new medications.
The examination will involve assessing the ear, including the appearance of the pinna, particularly inspecting for any deformities such as microtia or anotia. Otoscopic examination of the external auditory canal and tympanic membrane is crucial, with special attention on the attic for cholesteatoma. An examination should also include assessment of cranial nerves, a full neurological assessment, and assessment of balance, depending on the age of the child.
With the implementation of the Universal Newborn Hearing Screening program, today, most patients are identified within a few months after birth, with intervention started by 6 months.
Evaluation
Hearing assessment in children is age and ability dependent and will be addressed per age group here.[9]
Neonates
Otoacoustic Emissions
In the UK, all newborns and those who require less than 48 hours of special care in neonatal intensive care (NICU) are offered evoked otoacoustic emission (OAE) testing within the first 4-5 weeks of birth as part of a Newborn Hearing Screening Programme.[9] Otoacoustic emissions are outer hair vibrations that are detected in the external auditory canal in response to a click stimulus. This test is easy to perform and does not involve a general anesthetic.
Automated Auditory Brainstem Response
This investigation is offered to all newborns who have spent over 48 hours in the neonatal intensive NICU and is also offered to those who do not pass two OAE tests.[9] It involves measuring brainstem electrophysiological responses to click stimuli using electrodes placed on the scalp. This assesses hearing throughout the entire hearing pathway, from the external ear through to the brainstem.
6-8 months
Distraction techniques
An assistant engages the child’s attention, and the tester, whilst placed behind and to the side of the child, makes sounds of different intensities. The child is assessed to see whether they turn to the side of the noise.
9 – 36 months
Visual Reinforcement Audiometry
The child is placed at a table with some toys with two speakers on either side that produce sounds. If the child looks towards the speaker playing a sound, they are delivered a visual reinforcement (such as a flashing light).[10]
24-60 months
Conditioned Play Audiometry
The child is conditioned to perform a task in response to an auditory stimulus, such as placing a ball in a cup. Once the task is learned, the sound volume is reduced in order to determine their hearing threshold.
Over 60 months
Pure Tone Audiometry
A 5 years of age, most children can undergo pure tone audiometry. Hearing thresholds are determined by presenting sounds of various frequencies and at various intensities until the quietest sound is reliably detected 50% of the time. This test requires a higher level of attention and therefore is rarely done below the age of 5 years.
Other investigations
Additional investigations will be tailored to the precise clinical picture. In syndromic children, chromosomal testing is advised. There is also a role for imaging in the form of either computed tomography (CT) or magnetic resonance imaging (MRI)
Some authors advocate the measurement of renal function and testing for connexin-26, which is a marker who sensorineural hearing loss. In some children, imaging studies may prove useful and detect abnormalities of the cochlea or the cochlear nerve. Finally, ECG may be useful in children with Jervell Lange Nelsen syndrome. The ECG will reveal a prolonged QT interval, which can lead to syncopal attacks and death.
Treatment / Management
Treatment for hearing loss depends on the type of hearing loss present, the underlying cause and often there is an element of patient/parent preference.
Conductive hearing loss due to otitis media is treated with antibiotics. Some children may benefit from a myringotomy tube. Sensorineural loss cannot be treated with medical measures. Mild cases may be treated with amplification aids, and speech therapy is useful. However, amplification of sound can result in ear pain and discomfort.
Conservative management
A key element to managing hearing loss is family support and advice. There are a number of behavioral measures that can be used to improve hearing without the need for adjuncts or surgical intervention. The principles of this are rooted in creating a deaf-friendly environment, such as limiting background noise, talking face-on, and clear intonation. There are also a range of hearing assist devices that can be used, such as television listeners. It is also crucial that the child's educational support which could be in the form of special equipment or positioning in the classroom.
Hearing Aids
There are a variety of hearing aid types that are used in specific situations. Each type will be briefly covered here.
Binaural air conduction hearing aids rely on at least a partially functioning inner ear and central auditory processing system. They work by converting sound detected by a microphone into digital signals, which can then be amplified and re-converted into audible sounds that are transmitted to the ear. They can be classified based on whether these key parts are housed in an earpiece that sits externally (behind the ear), inside the canal (in-the-canal), or further inside the canal (in the ear).
Bone conduction hearing aids are typically used in conductive hearing loss when there are ear problems that impede the use of a regular air conduction hearing aid, such in children with external ear deformities (anotia, microtia) or when there are chronic ear infections. Bone-anchored hearing aids (BAHA) are fitted surgically under general anesthetic over two stages. A titanium implant is fixed into the temporal bone. Through this setup, a sound is conducted directly to the inner ear by way of the bone, bypassing the middle ear. Typically the BAHA is fitting from 4 years of age once the temporal bone has developed. However, soft-band bone conducting aids can be used from several weeks of age.
Contralateral routing of sound (CROS) hearing aids are used when there is unilateral sensorineural hearing loss. The sound in the problem ear is diverted to the better hearing ear without amplification. In cases where neither ear has normal hearing but one side is significantly better, a variation on this can be used called a BiCROS.
Cochlear Implant
Cochlear implants work by converting sound into digital signals that are transmitted directly to the auditory nerve via an electrode array. In the UK, the National Institute of Clinical Excellence (NICE) recommends cochlear implants in children who have severe to profound deafness in one or two ears with minimal benefit from conventional hearing aids after 3 months of use.[11]
Other options
Ventilation tubes are indicated in conductive hearing loss secondary to fluid ear or less frequently in the context of recurrent otitis media. They are inserted surgically and typically self-extrude on average a year of insertion. Children found to have cholesteatoma invariably require surgical clearance of the disease via a mastoidectomy.
Differential Diagnosis
Prognosis
The prognosis of hearing loss will vary considerably based on the underlying etiology. Congenital sensorineural hearing loss left untreated will invariably not improve or can progress, such as in the case of congenital CMV. On the other side of the spectrum, glue ear shows an excellent prognosis with the resolution of symptoms even without intervention.[12]
Enhancing Healthcare Team Outcomes
Hearing loss in the pediatric population must be managed as part of an interprofessional team. Most children with hearing loss are otherwise normal but, unfortunately, are often treated as if they have mental dysfunction. Thus the key is awareness and education of the caregivers and the public. Parents should be provided with resources by the social worker where they can seek specialized help.
Today, many states have social workers and a hearing loss nurse or developmental nurse dedicated to providing caregivers with the best school environment, the best form of communication, and the best resources. The nursing and audiology team should work with the clinicians to coordinate the cause of hearing loss and provide suitable treatment. Further, they should assist in patient education.
Other members of the team include medical doctors, including otolaryngologists, audiologists, speech therapists, geneticists, and pediatricians. In addition to this, audiologists, speech and language therapists, educational psychologists, and specialist nurses are vital parts of the wider team.
Communication is the most significant loss in people with deafness. Communication is vital for integration and socialization into society. Thus, every effort must be maintained to reverse the hearing loss. Today, most deaf children are taught to lip read and/or learn sign language. In addition, the hearing loss nurse should provide parents with information on devices like strobe lights connected to alarm clocks, doorknobs, and timers. Schools need to have a system so that the hearing loss child is able to hear any overhead announcements. All the latest TVs are now equipped with closed captioning.
Children who are deaf are at high risk for abuse, and thus a social worker should always follow these patients.
Delivery of the highest quality of care and support requires a coordinated approach amongst services, including between primary and secondary care. It is important to identify hearing loss at an early age because the earlier treatment is offered, the better the prognosis. [Level 5] [13]
Pediatric Hearing Loss