Pediatric Audiology Notes

Pediatric Audiology

Effects of Undiagnosed Hearing Loss in Children

  • Delays in receptive and expressive language, including reading.
  • Increased likelihood of inattentive or misbehavior.
  • Academic delays leading to vocational limitations.
  • Social isolation.
  • Widening academic gaps over time, making it difficult for children to catch up.
  • Delayed identification can result in auditory processing disorder (APD) and other problems.

Early Hearing Detection & Intervention Programs

  • Incidence of permanent hearing loss in infants is 1.5/1000.
  • Three key components:
    • Birth admission screening.
    • Follow-up screen & diagnostic.
    • Early intervention.

JCIH "1-3-6" Rule

  • Joint Commission on Infant Hearing (JCIH) established the "1-3-6" rule.
  • Screening by one month, diagnosis by three months, habilitation (hearing aids, therapy) by six months.
  • Federally mandated but state-run program to identify hearing loss in babies.
  • States require reporting of all infants diagnosed with hearing loss.
  • Early intervention services are offered to families through state agencies.

Causes of Permanent Hearing Loss in Infants

  • Unknown: 25\%
  • Maternal Infection, Complications after birth: 25\%
    • CMV exposure in utero, rubella in utero, etc.
    • NICU stay >5 days, ECMO very high risk
  • Genetic: 50\%
    • Recessive, dominant forms, X-linked.
    • Of these 50\%, 1/3 have syndromes (Usher, CHARGE, Down, Pendred, Turner, etc.).
  • Audiologists see many cases of non-permanent hearing loss in children related to otitis media.
    • Though medically reversible, these children can still experience speech/language delays; therefore, it’s important to be proactive with transient hearing loss when it is impacting a child’s development.

Symptoms of Hearing Loss in Young Children

  • Infant does not startle to loud sound.
  • Responds to visual but not auditory stimuli.
  • Does not acquire language and speech skills like peers.
  • Before universal infant hearing screening, many children with mild to moderate hearing loss were not identified until school age.

Pediatric Evaluation

  • A skilled pediatric audiologist has the following attributes:
    • Flexibility
    • Speed
    • Accuracy
    • Can put the big picture together; "high stakes" population
  • Remember to get the most important information first.
  • As a rule, always try to get a tympanogram (but if the kid is scared you may not be able to get the tympanogram first)
  • OAEs are great

Diagnosing Hearing Loss in Babies and Children

  • Use "Minimum Response Level (MRL)" rather than threshold.
  • Until age 4+, most children are not capable of responding at threshold.
  • Speech will always elicit a lower MRL than tones because speech is louder than tones are at the same dBHL level.
  • When deciding which test method to use, consider the developmental age, not the chronological age, of the child.
  • You usually do not use the down 10/up 5 method when testing children because you have limited time before attention wanes.
  • You usually can only obtain a few MRLs in a session, so move quickly!

Testing Infants

  • Infants < 6 months
    • Physiological measures (ABR/OAE) are the only measures that can be trusted at this age because behavioral responses are NOT reliable.
    • BOA (Behavioral Observation Audiometry)
      • Performed in sound field
      • Eye widening, sucking reflex, startle
      • Don’t consider BOA to be diagnostic, but is does provide valuable information
    • Challenges
      • Limited behavioral response due to poor postural control
      • Infants have little interest in responding to quiet sounds
      • Children with hearing loss may startle to loud sounds
    • Advantages
      • Sleep a lot!
      • That makes physiologic testing easier

Older Infants Through Toddlers

  • Babies 6 months – 2 years
    • Visual Reinforcement Audiometry (VRA)
      • Usually performed in sound field (remember that testing in sound field does NOT provide ear specificity)
      • Sometimes (very rarely) you can use headphones and get ear-specific information
      • Can use frequency specific tones/noises and speech (minimum response level)
      • 2 clinicians optimal (testing audiologist and “centering” audiologist, good communication important)
      • Conditioning the child to task is critical and may take time
      • Speech testing is usually a Speech Awareness/Detection Threshold (SAT or SDT)
        • "Uh-Oh!"
        • calling child’s name, singing songs
        • Some children may identify their nose, belly, eyes, etc. when asked
      • Speech Recognition/Reception Threshold (SRT) if you know that the child understood the stimulus word(s)

VRA Challenges

  • Child may lose interest quickly; must be strategic with which information you obtain first and be prepared to switch tasks often if needed to maintain their attention.
  • Child may be afraid of reinforcement toys!
  • With visual impairment may not be able to use VRA; use BOA and objective tests such as OAE.
  • Often can not rule out mild hearing loss because of minimum response level restrictions (young kids don’t always respond at threshold).
  • In sound field no ear-specific information is obtained.
  • Response is from the better ear.

Testing 2.5-4 years

  • Conditioned Play Audiometry
    • 2.5-4 years
    • Similar to an adult hearing exam except the child is given a more fun task than pressing a button or raising a hand
    • Can’t depend on reliable hand raise much before age 5
    • Conditioning to the task is crucial
    • Drop a block or peg in a bucket, stack blocks
    • Can be done in sound field, but usually under headphones by this age
      • Under headphones, you DO get ear-specific data
    • Can also test by bone conduction
    • Speech testing is often done first (before pure tones) by having child point to pictures or body parts. For older cooperative children with clear speech, you might be able to obtain an SRT just like adults.
    • Challenges
      • Be prepared to change tasks OFTEN, but you sometimes may need to keep the tasks the same for consistency. Must be flexible and intuitive to child’s needs

Age 5 and up

  • Similar to adult testing except for limited attention
  • Get most important information first
  • Get a couple threshold s in both ears before worrying about filling in the details
  • It’s fine to use play audiometry

Masking with Young Children

  • The introduction of a masking noise may confuse a child
  • If masking is not used, you must note in your report that the bone conduction thresholds reflect sensitivity of the better cochlea because masking could not be used
  • This is common with conductive hearing loss

Physiological Tests

  • Remember! Physiological tests are NOT a test of hearing.
  • However, they often correlate with hearing levels and for some populations they give you the best estimate of hearing (under 6 months the only good tool)
  • The best practice for both threshold determination and for showing that hearing has occurred is normally behavioral audiometry.
  • For young children you should combine behavioral and physiologic measures because it’s not always possible to get thresholds.
    • We say behavioral audiometry, when possible, is more precise because it requires a signal to be detected, perceived and acted upon (full hearing occurs in the brain)
    • Ascending and descending pathways
    • Physiologic tests for the most part don’t imply full perception/understanding
    • THE PROBLEM IS you can’t always get behavioral test results

Otoacoustic Emissions (OAEs)

  • Emissions originate in the outer hair cell of the cochlea (in a normal functioning ear) and the emissions travel outward through the middle ear bones and into the ear canal where we measure them with a sensitive microphone
  • The presence of OAEs rules out anything worse than a mild hearing loss
  • With a mild sensorineural loss, you may have OAES
  • With a loss that is moderate or worse you will have absent OAEs
  • GREAT FOR IDENTIFYING NONORGANIC LOSS
  • OAEs are found in normal functioning cochleae (mainly from the OHCs) VERY soft sound (-10 to 20dB SPL), inaudible without special equipment
  • People with normal hearing produce OAEs. A moderate or worse hearing loss (of any kind) will obliterate an OAE
  • OAEs are NOT neural signals; they are ACOUSTIC signals (sound) that emanate from the hair cells
  • Non-behavioral (often used as newborn hearing screen)
  • Quick

OAEs Assumptions

  • When we obtain OAEs, we can make some assumptions
    • Hearing is likely normal to no worse than a mild SNHL
    • Middle ear function is normal
    • You won’t see OAEs with a middle ear problem (even with a normal cochlea) because the middle ear problem will keep the emissions from getting out and being detected
  • Why OAE?
    • Physiological tests are the only reliable test under 6 months
    • To obtain ear specific information on a child when all you have is sound field
    • To confirm what you are getting behaviorally (in children and adults)
    • To assess for cochlear “dead regions” when you fit hearing aids
    • Quick and easy

OAEs Challenges

  • Patient must be still, quiet and the test room must be relatively quiet
  • If emissions are absent, it does not tell you the degree of hearing loss
  • Will be absent with middle ear disorders
  • The middle ear disorder makes it impossible for the emissions to get though and to be detected
  • OAE testing does not detect middle ear problems (that is done with immittance)
  • Therefore, even if the cochlea and the hair cells are normal, OAEs will be absent with a conductive hearing loss such as middle ear fluid

ABR Auditory Brainstem Response

  • Used to assess the neurological function from the VIII cranial nerve through the brainstem
  • A “neurologic” ABR is used to rule out tumors
  • A “threshold” ABR is used to make an estimate of the degree of hearing loss
  • ABR is just one of a family of tests known as “auditory evoked potentials.”
  • Characterized by a series of Waveforms I-V
  • NOT a test of hearing but highly correlated with hearing levels (i.e. when the nerve responds to a sound, we can infer that the person would perceive/hear that sound)
  • Must be still (no movement) and quiet: after 3 months generally have to test under sedation
  • Cooperative older children and adults usually don’t need to be sedated
  • Why ABR?
    • For babies/young children to identify hearing loss or confirm suspected hearing loss (can be a screening for newborns performed by a technician or a diagnostic evaluation to diagnose and quantify hearing loss performed by an audiologist)
    • Automated ABR is a screening
    • Diagnostic ABR may need to be under sedation
    • Sedated ABR is NOT a screening; it is diagnostic
  • Challenges
    • Patient must be asleep or at least at rest
    • Can have interference from electrical noise (surgical suites!)
    • Can be time consuming
    • Not as sensitive to finding tumors as MRI
  • Advantages
    • Unlike OAE, can get auditory information on all different hearing levels (not just normal and mild) to diagnose hearing loss
    • Often can get enough information to move forward with treatment plan (HA, CI, etc)

ASSR Auditory Steady State Response

  • Evoked potential test similar to ABR but can get estimates of a 4- frequency audiogram
    • Time consuming
    • More difficult to elicit than ABR
    • Usually under sedation
    • Provides better estimates of audiogram for hearing aid fitting
  • Note: OAE is pre-neural and both ABR and ASSR are pre-cortical (before the level of the cerebral cortex) so none of them are affected by sedation.