Medical Assessment

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  History and physical examination should assess

  
  
  
  
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    The onset, degree, progression, and developmental impact of hearing loss, particularly as it relates to the duration of deafness

    
    
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    Risk factors for hearing loss, including perinatal illnesses, prematurity, hypoxia, jaundice, need for neonatal intensive care or intubation, meningitis, exposures to ototoxic drugs, head injury, and family history of hearing loss

    
    
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    Other health problems that may preclude or increase the risk of a general anesthetic or may assist in determining if a syndrome is present

    
    
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    Other developmental milestones, particularly evidence of cognitive deficits

    
    
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    Physical signs of syndromic features, craniofacial anomalies, conductive hearing loss, or otitis media.

  
  

Audiologic Assessment

To allow early determination of the presence and degree of hearing loss, electrophysiological measures are used when behavioral measures are inappropriate or inaccurate. This should take the form of newborn hearing screening soon after birth, followed by some combination of frequency-specific auditory brainstem response (ABR) testing, auditory steady-state response (ASSR) testing, otoacoustic emission (OAE), and tympanometry. Each test has unique characteristics and a combination of some or all of these are usually required to give the most comprehensive picture of the child’s auditory capabilities, including the severity and site of hearing loss. For the population of children with severe to profound SNHL, this early assessment aids in forming an estimate of amplification requirements, mobilization of the care team for close observation of the child’s progress, as well as early planning for possible future interventions, thus avoiding treatment delays.

In almost all cases, electrophysiological testing is sufficient to estimate the hearing levels for the purpose of fitting conventional amplification. Importantly, however, such testing methods may have some unique challenges that are critical in managing children with SNHL. Although OAEs are generally absent in children with severe to profound hearing loss, they can be present in children with auditory neuropathy spectrum disorder (ANSD). ANSD affects 10% to 14% of newly diagnosed children with severe to profound bilateral SNHL. These test results, taken in isolation, can inappropriately suggest less severe hearing loss. Similarly, the unique ABR waveforms seen in ANSD often require an experienced clinician to detect. Typically, the cochlear microphonic (CM) waveform is present with absent or abnormal ABR waveforms. The CM waveform is distinguished from artifact by demonstration of inversion of the response with inversion of the signal polarity stimulus ( Fig. 1 ). Thus, identification of the CM waveform requires a protocol that includes both rarefaction and condensation stimuli. The CM waveform is further distinguished from artifact by a loss of response when disconnecting the sound tubing. The ANSD phenotype is not diagnosable on ASSR so ABR is needed to make this diagnosis. Tympanometry can support bone conduction ABR testing and clinical examination in the identification of a conductive component to the hearing loss.

ABR waveform in a patient with bilateral auditory neuropathy-dyssynchrony. Note presence of CM waveform with absence of the ABR waveform at stimulus levels as high as 90 dB HL. Note also reversal of the CM waveform with change in the signal polarity (condensation vs rarefaction).

Behavioral testing using visual reinforcement audiometry can accurately confirm the severity of hearing loss in children around 6 to 8 months of age. Behavioral thresholds are particularly important in children with ANSD because the ABR is unable to determine hearing thresholds for fitting amplification. This kind of testing can be challenging in children with severe to profound SNHL due to their lack of familiarity with sound. Those with concurrent global developmental delay can also have less consistent conditioned behavioral responses.

Imaging

Imaging is critical in children with significant hearing loss because it can aid in identifying a cause, possibly predict hearing loss progression, and potentially identify those with a poor prognosis for speech development using HAs or CIs. Imaging can take the form of MRI with or without high-resolution computed tomography (HRCT) of the temporal bone structures and brain. Imaging allows anatomic assessment of the labyrinth, cochlea, cochleovestibular, and facial nerves. It also identifies concurrent brain disease. A diagnosis of cochlear nerve deficiency (CND) or significant cochlear or labyrinthine abnormalities may either preclude the use of a CI or predict a low chance of achieving open-set speech perception.

CND is present in approximately 1% of children with bilateral SNHL, most often in the setting of severe to profound thresholds. Labyrinthine abnormalities have been detected in up to 40% of children with SNHL and can range in severity. Identification of both CND and inner ear malformations allows the treating team to provide realistic expectations to families about outcomes with the various interventions and to maximize communication by augmenting auditory-verbal communication with nonauditory forms. Detecting abnormalities of the facial nerve can help guide safe CI surgery, particularly in the setting of semicircular canal abnormalities ( Fig. 2 ).

Intraoperative photograph of a left transmastoid view of the facial nerve running inferior to the stapes superstructure in the setting of an absent lateral semicircular canal.

High-resolution MRI with a 3-dimensional Fourier transformation constructive interference steady-state protocol is the most sensitive for diagnosing CND and has the unique ability to assess for concurrent brain disease, which may be present in up to 40% of pediatric CI recipients. HRCT is complementary for assessing labyrinthine anomalies ( Fig. 3 ), other temporal bone disease, and the presence and pathway of the fallopian canal. One shortcoming of HRCT as a single imaging modality is that it cannot identify CND in the setting of a normal caliber internal auditory canal. Both MRI and HRCT are important in assessing cochlear patency in children suffering from hearing loss secondary to meningitis ( Fig. 4 ).

Labyrinthine malformations ( A – C ) are varieties of cochlear incomplete partitions. ( A , B ) are variations on the spectrum of incomplete partition with enlarged vestibular aqueduct. ( C ) X-linked stapes gusher (deafness) morphology. ( D – F ) Varying degrees of cochlear hypoplasia with or without semicircular dysplasia. ( D ) Marked and ( E ) moderate hypoplasia. ( F ) Cochlear hypoplasia with a small vestibular remnant and absent semicircular canals characteristic of CHARGE association. ( G , H ) Common (cystic) cavity deformities of the cochlea and vestibular vestige.

Hyperdensity on HRCT ( A ) and loss of hyperintensity on constructive interference in steady state (CISS) MRI sequence ( B ) in the left basal turn of the cochlea consistent with postmeningitic obstruction and ossification.

Other Common Testing

These tests may be useful in identifying the cause of the hearing loss and risk of transmission to future off spring, associated medical conditions that may require early treatment, and potential prognosis for progression of hearing loss and performance with CIs:

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  Electrocardiogram (Jervell and Lange-Nielsen syndrome)

  
  
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  Cytomegalovirus (CMV) testing of urine and Guthrie card

  
  
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  Connexin 26 and 30 gene sequencing and other genetic testing

  
  
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  Urinalysis (Alport syndrome in older children)

  
  
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  Retinal examination and visual acuity testing (Usher’s syndrome)

  
  
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  Renal ultrasound in children with branchial anomalies (branchio-oto-renal syndrome)

  
  
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  Investigations for concurrent medical conditions as the history and examination indicate

  
  
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  Comprehensive, molecular genetic testing.

Communication Options and Intervention

Communication options for children with severe, severe to profound, and profound hearing loss include verbal and nonverbal strategies (ie, sign language). Although nonauditory approaches to verbal communication through lipreading were commonplace in the past, auditory approaches have become more common in recent times, owing to better outcomes. Auditory supplementation through amplification when possible or cochlear implantation allows for improved sound awareness, enhanced lipreading, speech understanding, and vocal control. These are the underpinnings for optimal auditory-oral communication development.

As a matter of ethical and moral obligation to these children, appropriate resources should be made available for learning about verbal and nonverbal communication strategies. Auditory-oral communication supplemented through amplification and/or cochlear implantation results in the highest levels of educational achievement and employment opportunities for hard-of-hearing and deaf children. Importantly, informed parental choice remains the single most important determinant in such decisions because self-determination is not possible at such an early age. To advocate for a delayed choice at this early age is, by default, a decision for nonverbal communication because delayed intervention, beyond the critical period for speech and language development in the brain, rarely results in age-appropriate auditory-verbal skills. Because 95% of hard-of-hearing and deaf children are born to 2 hearing parents, auditory-oral communication is the dominant choice because this represents a more familiar strategy for these families.

For families that choose to pursue auditory-oral communication for their child, a referral to an appropriate early intervention specialist, and fitting of HAs by a pediatric audiologist should be carried out as early as possible to maximize each child’s access to sound. The Joint Committee on Infant Hearing recommends that HA fitting occur before 3 months of age and that an early intervention program is in place by 6 months of age. It is critical that each child be closely observed for speech and language progress by a variety of well-trained professionals (audiologists, speech-language pathologists, pediatricians, and otolaryngologists). By necessity, this patient population requires high-gain amplification with resulting issues of feedback, distortion, cerumen impaction, and occasionally otitis externa. Additionally, otitis media can be problematic in this age group and can add conductive hearing loss to the underling SNHL. Close collaboration between the treating audiologist and otolaryngologist is needed to minimize the impact of these medical issues. If a given child is making adequate progress with HAs alone, then continued close observation is appropriate. In most instances, children with severe to profound SNHL do not make age-appropriate gains despite correctly fitted amplification. In such cases, cochlear implantation should be considered to achieve auditory-verbal language.