Hearing: Answers

Question 1.   What is the pediatrician’s responsibility for assessing language delay?  When language delay is suspected, what is the Pediatrician’s responsibility for evaluation/management?

Answer:  If a child is not able to hear sounds in the speech spectrum —250 through 4,000 hertz, then it is unlikely that he/she will be able to produce those speech sounds correctly.  Furthermore, most speech and language learning takes place from birth to about 3 years of age, so the longer that a child has a hearing loss during this critical time period, the poorer the long term prognosis becomes with regard to speech and language development; and the single best predictor of school success in a school aged child is the child’s speech and language skills.  Hence, it is the Pediatricians responsibility to perform surveillance of developmental milestones, auditory skills, parental concerns and middle ear status in the medical home for all infants.  The Pediatrician must use a validated assessment tool, such as the Denver 2 to perform an objective standardized screening of global development at 9, 18 and 24 to 30 months of age or at any time if the health care professional or family has concern.  Infants who do not pass the speech-language portion of the medical home global screening or for whom there is a concern regarding hearing or language should be referred to an audiologist for a full audiologic assessment, as well as to an agency such as early intervention for a speech-language evaluation and therapy.

If hearing loss is confirmed, other referrals may also be required for further treatment or evaluation, such as to Otolaryngology, Ophthalmology and Genetics.

Question 2:  How is hearing loss classified?

Answer:  Hearing loss is classified by degree, type and number of ears effected.   . 

The degree of hearing loss is measured in decibels of hearing loss (dB HL).

                                Normal                           -10 to 15 dB HL

                                Borderline or Minimal    16 to 25 dB HL

                                Mild                                 26 to 40 dB HL

                                Moderate                         41 to 55 dB HL

                               Moderate-severe               56 to 70 dB HL

                               Severe                               71 to 90 dB HL

                               Profound                           >90 dB HL

The type of hearing loss is a description of the location of the auditory disorder.

--Conductive—reduction of air-conductive sound delivered to the normal cochlea during transmission through a disorder of the outer ear and/or middle ear.  (i.e., in OME or cerumen impaction—approx 25 dB HL, in complete atresia up to 60 dB HL)

--Sensory—damage to outer and/or inner hair cells of the cochlea.  Causes variable degrees of hearing loss.

--Mixed—Both sensory component overlying conductive component (i.e. child with sensory loss who experiences OME)

--Neural—Deficit in neural transmission at the auditory (8’th cranial) nerve.  Outer ear, middle ear and cochlea intact.

--Central—Processing deficit at higher levels of the central nervous system.  Conductive, sensory and neural pathway intact.

The number of affected ears:

                              Bilateral

                              Unilateral

Question 3:  What behavioral audiologic test would be helpful to evaluate Tommy’s hearing? 

Answer:  Several behavioral tests are available to obtain hearing thresholds for children.  Selection of a behavioral test is based on the childs developmental age.

The commonly available behavioral tests include the following:

                        Behavioral Observation Audiometry

Useful for children whose developmental age is younger than 6 months.

Test description:  While the child sits on the parents lap, auditory stimuli are presented through two external speakers to the child’s right and left, and the audiologist looks for behavioral changes to indicate that the child has heard the stimulus. 

Approx time to administer:  30 min. 

Advantages:  Can exclude a severe to profound hearing loss. 

Disadvantages:  Does not exclude mild to moderate hearing loss or unilateral hearing loss.  Does not give ear specific information—assesses hearing of the better ear only.  Does not give threshold

.—Not appropriate for Tommy.  Does not give maximal information.

                        Visual Reinforcement Audiometry

Useful for children whose developmental age is 6 months to 3 years.

Test description:  While the child sits on the parents lap, auditory stimuli are presented through two external speakers to the child’s right and left, and when the child looks for the sound an animated toy is turned on to reinforce the behavior. 

Approx time to administer—30 min. 

Advantages:  can be used to obtain thresholds. 

Disadvantages:  Does not exclude unilateral hearing loss.  Does not give ear specific information—assesses hearing of the better ear only.

—Is appropriate for Tommy.  Gives maximal information based on his developmental ability.

                        Conditioned Play Audiometry

Useful for children whose developmental age is 3 to 5 years. 

Test description:  The child wears headphones and/or bone vibrator through which stimuli are presented.  When the child appreciates the stimuli he performs a task for which he is conditioned, such as drop a block in a bucket.

Approximate time to administer—30 min.

Advantages—Ear specific information can be obtained, as well as differentiation between conductive hearing loss and sensorineural hearing loss.  Speech Recognition Threshold (SRT), which correlates with Pure Tone Audiometry, can be obtained.  SRT is the lowest intensity at which a child can repeat two syllable words.  Speech discrimination ability is the percentage of one syllable words that the child can repeat correctly at a comfortable listening level which is typically 40 dB louder that SRT. 

Limitations:  attention span of child may limit available information.

—Not appropriate for Tommy.  Unable to follow commands.

                        Conventional Audiometry

Useful for children whose developmental age is  greater than 5 years. 

Test description:  Same procedure as conditioned play audiometry except that the child raises his hand or presses a button in response to the stimuli. 

Advantages: as described in CPA.

Limitations:  depends on cooperation of child.

--Not appropriate for Tommy.

Question 4:  What electrophysiologic test would be helpful to further asses the etiology of Tommy’s hearing loss?

Answer:  Electrophysiologic tests are either used for children who can not complete behavioral testing (i.e., Otoacoustic Emissions or Auditory Brainstem Response used in newborn screens and discussed below) or to asses the function of a portion of the auditory system i.e., tympanometry to assess middle ear function.  The electrophysiologic test that would be particularly important to perform on a child like Tommy with a history of OME, therefore, would be tympanometry.

            Tympanometry is not a hearing test and does not measure hearing thresholds.  It does evaluate the function of the middle ear, by measuring tympanic membrane compliance and ear canal volume.  A probe is placed firmly against the external ear canal opening to create a seal.  The pressure within the ear canal is changed from negative to positive.   A normal healthy TM should have a peak compliance when pressure is equal on both sides of the TM.  A child’s normal ear canal volume is between 0.5 to 1 m.

            Certain common middle ear disorders present with characteristic tympanometry measures:

             Disorder               Middle ear pressure peak         Ear canal volume

   Eustachian Tube dysfunction  Peak worse than -50daPa         Normal

   Middle ear fluid                    No peak                                   Normal

   TM perforation/tube             No peak                                   Large

   Occluded ear canal               No peak                                   Small

Question 5:  Tommy Toddler comes back to you for follow up after the audiologic tests were performed.  His mother hands you the raw results of the audiologists report, but she does not have the interpretation, and you did not receive a consult report from either audiology or otolaryngology.  The mother has a follow up apt with otolaryngology, but she is understandably concerned and asks you “what does it mean?”  Please interpret Tommy’s audiology report with respect to type and severity of his hearing loss.  See attatched.

Answer:  Tommy has a bilateral conductive hearing loss in the mild range.  Note that the air conduction thresholds are outside of the normal range at 25 decibels,  but the masked bone conduction is in the normal range.  Tommy’s tympanogram reveals that he has middle ear fluid.  Note that there is no middle ear pressure peak and his ear canal volume is normal.

Question 6:  What are the treatment options available to Tommy and his family?

Answer:  Despite adequate therapy for AOM, asymptomatic middle ear effusions persists in 40% at one month, 20% at 2 months and 10% at three months.  In the 10-15 % of children in whom the fluid does not clear, it may need to be removed to promote healing and resolution of conductive hearing loss (i.e., tympanostomy tubes).  If  Tommy’s conductive hearing loss is treated, he would then have an approx 25 db improvement.  Continued early intervention, speech therapy and a multidisciplinary approach will also enhance outcomes.   

Case 2:  Nelly Newborn, a 5 day old former 39 week gestational age female who was discharged from the well baby nursery 3 days ago, comes to see you for her first well child care visit.  Nelly’s mother is very concerned because she was informed by the hospital staff that Nelly failed her newborn hearing screen in her right ear.  Nelly has a follow up out-patient screen scheduled in 2 weeks, but not an appointment for a full audiological evaluation and Nelly’s mother is not sure if this is “all right”.

Question 1:  What advice do you give Nelly’s mother?

Answer: “Unidentified hearing loss at birth can adversely affect speech and language development as well as academic achievement and social-emotional development.  Historically, moderate to severe hearing loss in young children was not detected until well beyond the newborn period and mild or unilateral hearing loss was often not diagnosed until the child reached school age. (JCIH 2007 position statement)  Therefore,  the Joint Committee on Infant Hearing, the AAP, and others have endorsed a policy of universal newborn hearing screening, the latest position statement of which is the “Year 2007 Position Statement :  Principles and Guidelines for Early Hearing Detection and Intervention Programs”.    This statement outlines a time course of intervention and has 2 separate protocols—one for the well baby nursery and one for the NICU.  The Well baby protocol states that if an infant does not pass her newborn hearing screen, she should have a repeat outpatient hearing screen before one month of age.  If  she does not pass this, either, then she should have a full pediatric Audiologic evaluation and medical evaluation before 3 months of age.  If hearing loss is confirmed, the family should be informed in a culturally sensitive manner, the patient should be reported to the state early hearing detection and intervention program, referrals should be made for early interventions services, and a referral should be made to an otolaryngologist to review her medical and surgical options, and begin fitting for amplification devices if appropriate.  Before 6 months of age, the pt should receive additional appropriate referrals which would include a referal to genetics, otolaryngology, opthalmologiy and others as dictated by her medical evaluation.  Early intervention services should begin as soon as possible after diagnosis but at no later than 6 months of age.  “A growing body of literature indicates that when identification and intervention occur at no later than 6 months of age for newborn infants who are deaf or hard of hearing, the infants perform as much as 20 to 40 percentile points higher on school related measures (vocabulary, articulation, intelligibility, social adjustment, and behavior).”

Question 2:  What are the accepted audiologic tests for newborn hearing screening in the well baby nursery?

Answer:  Both evoked Otoacustic Emissions (OAE) and automated Auditory Brainstem Response (ABR) are acceptable for universal newborn hearing screening in the well baby nursery since they are noninvasive , easily performed in newborns, and can be administered in 10 to 15 minutes with reproducible results, not dependent on interpretation. 

                        OAE measures outer hair cell function of the cochlea. 

Useful at any age.

Test description:  Small probe containing a sensitive microphone is placed in the ear canal for stimulus delivery and response detection.

Approximate time to administer:  10 minutes

Advantages:  Ear specific results, not dependent on whether patient is asleep or awake, quick time test.

Disadvantages:  infant or child must be relatively inactive during the test, not a true test of hearing because it does not assess brain stem or cortical processing of sound—would miss brain stem and cortical pathology.

                        ABR measures activity in auditory nerve and brainstem.

Useful at any age.

Test description:  Placement of electrodes on child’s head detects auditory stimuli presented though earphones.

Approximate time to administer:  15 minutes

Advantages:  Ear specific results, responses not dependent on patient cooperation.

Disadvantages:  Infant or child must remain quiet/sedated, not a true test of hearing because it does not assess cortical processing of sound.

            OAE is an acceptable first test in the newborn nursery protocol where there is a low incidence of acoustic nerve pathology.  However, in the NICU, where there is a higher incidence of infants with nerve damage, OAE is not acceptable since it measures response through the level of the cochlea only, and would miss acoustic nerve pathology. ABR is the required test for screening NICU newborns.  Furthermore, if a NICU infant fails the hospital screening ABR, she should be referred directly for a full Pediatric Audiologic evaluation, and not for a repeat outpatient procedure.

Question 3:  When Nelly comes back for her 1 month well child visit, Nelly’s mother tells you that although Nelly failed her first newborn screen in her right ear, she had both ears retested and passed her second outpatient screen, much to her mother’s relief.  Her mother then informs you that the reason that she was so worried initially was that she did not want Nelly to have to go for a full audiologic evaluation, since she knows how long they take since she has a family member who developed permanent hearing loss as a child.  What discussion do you now have with Nelly’s mother?

Answer:  Several risk factors have been associated with hearing loss, and are indications for subsequent full pediatric audiologic evaluation.  These risk factors are generally broken into those affecting hearing from birth to 28 days and those affecting hearing from 29 days to 24 months—also referred to as risk factors for late onset hearing loss.  Any risk factors are an indication for full pediatric audiologic evaluation.  Risk factors that occur in the “late onset” group require a full evaluation by Pediatric Audiology between the ages of  24 to 30 months, even if the baby passed the newborn hearing screen.  For the list of risk factors please see attached table:  Pediatrics Vol. 111 No 2 February 2003  “Hearing Assessment in Infants and Children:  Recommendations Beyond Neonatal Screening”  p. 437, Table 1.