A 2 year old female presents to your office with her mother who is concerned that unlike her other children, her youngest daughter is not talking. Her child has a very limited vocabulary consisting of only word fragments such as "ma." She interacts with her parents and older siblings by grunting and pointing to objects. She cries when she does not get her way. Her mother has recently noticed that her daughter seems to ignore her unless she looks straight at her while speaking. Her mother feels that her child is otherwise normal since she likes to watch cartoons and play with dolls. Her child's past medical history is significant for numerous middle ear infections. Her immunizations are all up to date. Her birth history is normal.

Exam: VS T 37, HR 120, RR 24, BP 90/60. Height 89 cm (35 in) (75%ile), weight 13.2 kg (29 lbs) (75%ile). She appears well, in no acute distress. Her eyes are normal. Her tympanic membranes in both ears show some scarring and thickening. Oral mucosa is moist. Neck is supple without adenopathy. Heart regular. Lungs are clear. Abdomen is soft and non-tender. She is shy, so her speech is difficult to assess. A neurologic examination finds no abnormalities. She has age appropriate gross motor and fine motor skills.

Based on the history reported by her mother, you recommend that she undergo comprehensive audiology testing which reveals a bilateral moderate conductive hearing deficit attributed to repeated episodes of otitis media. Possible considerations at this point include: 1) Surgical tympanostomy tubes if she continues to have frequent episodes of otitis media. 2) Hearing aids with speech and audiology therapy sessions followed by special education preschool if language milestones are not age appropriate by the time she is 3 years of age.

The most critical period for the development of hearing and speech occurs in the first 6 months of life. Moderate to severe hearing impairments, as well as mild or unilateral hearing deficits, during the first year of life are known to affect speech, language, cognitive and behavioral development in children. In infants younger than 6 months of age, early intervention is thought to improve the development of speech, language, and cognition, which in turn, decreases the need for special education (1). Deafness is more prevalent than any other disabling condition for which mandated neonatal screening programs exist (2).

Each year, approximately 5000 infants are born in the United States with moderate to profound, bilateral permanent hearing loss (3). The prevalence of moderate to profound hearing impairment in newborns, including sensorineural (SNHL) and conductive hearing loss (CHL), is approximately 1 to 3 per 1,000. There is an approximate 2-fold increase in this number when infants with mild SNHL are included (1).

The prevalence of hearing impairment increases considerably in newborns that have any of the following risk factors as described by the Joint Committee on Infant Hearing, Year 2000 Position Statement (1,4):
. . . . . - An illness or condition requiring admission of 48h to a neonatal ICU.
. . . . . - Stigmata or other findings associated with a syndrome known to include a sensorineural or conductive hearing loss.
. . . . . - Family history of permanent childhood sensorineural hearing loss.
. . . . . - Craniofacial abnormalities, including those that have morphologic abnormalities of the pinna and ear canal.
. . . . . - In utero infection, such as cytomegalovirus (CMV), herpes, toxoplasmosis, or rubella.

The Joint Committee on Infant Hearing, Year 2000 Position Statement also illustrates specific risk indicators associated with progressive or delayed-onset hearing loss (1,4):
. . . . . - Parental or caregiver concern regarding hearing, speech, language, or developmental delay.
. . . . . - Family history of permanent childhood hearing loss.
. . . . . - Stigmata or other findings associated with a syndrome known to include a sensorineural or conductive hearing loss or Eustachian tube dysfunction.
. . . . . - Postnatal infections associated with a sensorineural hearing loss, including bacterial meningitis.
. . . . . - In utero infection, such as CMV, herpes, toxoplasmosis, rubella, or syphilis.
. . . . . - Neonatal indicators, specifically hyperbilirubinemia at a serum level requiring exchange transfusion, persistent pulmonary hypertension of the newborn associated with mechanical ventilation, and conditions requiring the use of extracorporeal membrane oxygenation.
. . . . . - Syndromes associated with progressive hearing loss (i.e., neurofibromatosis, osteopetrosis, Usher syndrome)
. . . . . - Neurodegenerative disorders (i.e., Hunter syndrome) or sensory motor neuropathies (i.e., Friedreich's ataxia, Charcot-Marie-Tooth syndrome)
. . . . . - Head trauma.
. . . . . - Recurrent or persistent otitis media with effusion for at least 3 months.

Neonatal Hearing Screening

Sensitive techniques are available for performing neonatal hearing screening, and early intervention has been shown to positively affect language development in hearing impaired children (2). Prior to the mandate of universal newborn hearing screening (UNHS) programs in at least 32 states in the United States, the average age that children were diagnosed with hearing impairments was approximately 30 months. Children who had mild or moderate hearing losses often were not identified until entering school. Studies have shown that even targeted screening of high-risk groups can identify only up to 50% of children who have significant hearing impairments prior to the development of speech (1).

Initial screening for hearing deficits is conducted within the hospital following the birth of a newborn and depending on the results, additional screening may be implemented prior to or following discharge. Currently utilized screening methods include automated auditory brainstem response (AABR), transient evoked otoacoustic emissions (TEOAE), and distortion product otoacoustic emissions (DPOAE). These methods incorporate a device that objectively and automatically detects one's response to sound presented as an evoked potential or an otoacoustic emission. These screening techniques reveal whether specific stimulus levels elicit a response. These screening tests are unable to provide a quantitative estimate of the severity of the hearing deficit and cannot distinguish SNHL from CHL (1). The auditory brainstem response (ABR) test (also known as brainstem auditory evoked response-BAER), which is an electrical waveform or an evoked potential (similar to electroencephalography) produced by auditory nerve and brainstem activity following a click or other brief sound. ABR testing is independent of behavior and is influenced by the intensity and rate of stimulation. The presence of an ABR indicates that sound is perceived by the test subject. Abnormal ABR patterns have been shown to correlate with hearing deficits and enables the differentiation between CHL and SNHL. Like any test, the validity, efficiency and test result interpretation is a function of the test administrator's skill and experience (1).

The transient evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) both work on the principle in which a sound stimulus (such as a click) causes the cochlea to form an emission. This emission can be detected by placing a microphone in the ear canal connected to a computer specially designed to analyze this emission.

The current American Academy of Pediatrics guidelines recommend that hearing deficits are identified by 3 months of age and intervention initiated by 6 months of age (1). A review by Clemens and Davis (5) reports that the false-positive rates of previously reported UNHS (universal newborn hearing screening) programs range between 2.5 and 8%. Higher false-positive rates may lead to a variety of unnecessary negative effects, including emotional trauma, disease labeling, iatrogenic adverse events from unnecessary testing, and increased expense in terms of time and money. Clemens and Davis have shown that simply rescreening all infants who failed their initial UNHS before hospital discharge reduced the false-positive rate to 0.8% (5). Sokol and Hyde report that a maximum false-positive rate of 3% is generally acceptable for hearing screening programs (1). It is important to recognize that screening tests in high- and low-risk groups will yield different results due to variation in the presentation and distribution of hearing disorders within these groups and the fact that it is easier to achieve ideal testing conditions and results in babies who are sleeping, less distressed, and in low-risk groups (1).

There are some disadvantages with the UNHS programs. Sokol and Hyde's review (1) indicates that it is important that UNHS programs include follow-up of those infants who fail in-hospital screening or are not successfully screened before discharge due to shorter hospital stays and/or poor compliance with following-up on those who fail the first screen. One should also note that passing a UNHS program does not automatically indicate that an infant has normal hearing. Furthermore, acquired hearing disorders due to congenital (i.e., CMV) or acquired infections (i.e., meningitis), acquired conductive hearing impairment (due to recurrent otitis media infections), or auditory neuropathy will not be detected by UNHS programs (1).

UNHS programs have enabled earlier identification, diagnosis, and intervention of hearing deficits in infants. Sokol and Hyde's report (1) suggest that early intervention improves speech, language, cognition, and social skills through the use of interventions such as hearing aids and cochlear implants (1).

Post-Neonatal (older ages) Hearing Screening

Approximately 5-10% of newborns will display one of the risk factors for progressive or late-onset hearing loss described by the Joint Committee on Infant Hearing (1,4). Sokol and Hyde (1) suggest that infants who are at risk for developing hearing loss that manifests after neonatal screening (i.e., perinatal CMV infection) should be rescreened every 3 to 6 months for at least 3 years. (1,4).

Other conditions that may affect hearing including bacterial meningitis or head injury, should also be evaluated appropriately using screening methods such as DPOAE (distortion product otoacoustic emissions), TEOAE (transient evoked otoacoustic emissions), or the more accurate AABR (automated ABR screening) test. Postnatal screening failures should be followed up by full comprehensive audiologic and otologic examination.

Some of the best tests for evaluating hearing deficits in infants older than 6 months of age includes behavioral tests such as visual reinforcement audiometry (VRA) which evaluates one's response to specific tones projected within a soundproof room from various locations. VRA can accurately evaluate children 6 months of age and older who have normal neurological development. The reliability and accuracy of behavioral tests are limited in infants who are younger than 6 months of age or have developmental delays or certain physical disabilities (1).

The behavior of the child and environmental noise levels may affect the results of hearing screening in infants. OAE and AABR testing are most accurate when the child is preferably sleeping or resting quietly, which can be difficult in children greater than 6 months of age. If this is not possible, mild sedation or light general anesthesia may provide a better testing environment in these children (1). For children older than 6 months of age without cognitive impairments, behavioral screening by VRA or conditioned play audiometry (CPA) is acceptable. CPA is where the child is conditioned to make a response using common play materials (e.g., being taught to drop a block into a bucket) when hearing a sound stimulus. Informal behavioral screening using noisemakers and observing a child's response is inaccurate. Evaluating children with substantial cognitive disorders is more complex and challenging and requires long-term evaluation (1).

Screening preschool-aged children under a Early Hearing Detection and Intervention program may identify preschoolers who have developed hearing deficits that have presented following birth, are progressive, or associated with diseases (i.e., meningitis) or head trauma. This impairment may hinder further development of hearing, speech and language (1). Middle ear conditions are common in 3 to 5 year old children, and it is important for health care professionals to screen for both hearing loss and middle ear problems. The objectivity of OAE screening makes it ideal for cooperative children. CPA, which has the capacity of evaluating the full perceptual system of a child, can also be used for screening cooperative, responsive 3- to 5- year olds with an experienced tester. Children who cannot perform sufficiently on CPA can be tested successfully with VRA. Screening errors can be prevented by conducting both objective and behavioral testing, where practical. Screening failures in this group should also be followed by full audiologic assessment (1).

Failing an objective screen in a child should alert health care professionals to determine whether the failure is caused by middle ear disease. Tympanometry is used to detect middle ear conditions by utilizing varied air pressures to assess the compliance of the tympanic membrane. For example, an acute otitis media will result in low compliance indicating a stiff tympanic membrane because the space behind the tympanic membrane is filled with fluid. A normal tympanogram increases suspicion for SNHL and should be followed up by a comprehensive diagnostic audiologic assessment. An abnormal tympanogram suggests that the screening failure is probably a result of a middle ear disorder. One should remember that abnormal tympanograms do not necessarily rule out a sensorineural component of hearing loss (1).

Detailed guidelines for hearing screening protocols for children are available in the Joint Committee on Infant Hearing 2000 position statement (4).

Questions

1. True/False: In infants younger than 6 months of age, early intervention for hearing impaired infants is believed to improve the development of speech, language, and cognition, which in turn, decreases the need for special education.

2. Name some in utero infections which are known to cause hearing abnormalities.

3. True/False: Current screening methods including automated auditory brainstem response (AABR), transient evoked otoacoustic emissions (TEOAE), and distortion product otoacoustic emissions (DPOAE), are able to distinguish whether a child has sensorineural or conductive hearing loss.

4. What is the best test for assessing hearing deficits in infants older than 6 months of age?

5. After failing an objective hearing screen, tympanometry testing is conducted and the results are abnormal. What does this suggest?

6. True/False: OAE and AABR methods are most accurate when the child is resting quietly or sleeping.

References

1. Sokol J, Hyde M. Hearing Screening. Pediatr Rev 2002;23(5):155-161.

2. Stockard-Pope JE. Auditory development and hearing evaluation in children. Adv Pediatr 2001;48:273-299.

3. Thompson DC, McPhillips H, et al. Universal newborn hearing screening: summary of evidence. JAMA 2001;286(16): 2000-2010.

4. Joint Committee on Infant Hearing. Joint Committee on Infant Hearing Year 2000 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Programs. Audiology Today 2000;Special Issue:6-27.

5. Clemens CJ, Davis SA. Minimizing false-positives in universal newborn hearing screening: a simple solution. Pediatrics 2001;107(3):E29.

Answers to questions

1. True

2. TORCH: toxoplasmosis, rubella, CMV, herpes

3. False

4. Best test for this age group: Behavioral tests that rely on operant conditioning, such as visual reinforcement audiometry (VRA) involves testing one's response to specific tones projected within a soundproof room from different locations.

5. Screening failure is attributable to middle ear disease. Yet, this does not completely rule out a sensorineural defect.

6. True