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Our Experience in Diagnostic of Hearing Impairments by Small Children using OAE and ABR

J. Spiridonova, D. Popova

Department of Otorhinolaryngology, Medical University, Sofia, Bulgaria

ABSTRACT

Objective: The purpose of this artical is to develop and establish a valid method of screening newborn hearing using an universal early indentification programme.
Study design: The study design was a retrospective case review.
Setting: Clinic of Ear, Nose and Throat diseases, Sofia, Bulgaria.
Patients: The study included patients suffering from hearing loss.
Main outcome measure: These included clinical development, diagnosis and therapeutic strategies to patients.
Results: After examining 286 infants, sensoneural hearing loss is identified in 216 infants using OAE /TEOAE and DPOAE/ and ABR measurments.
Conclusion: It is very important to reduce the average age of identification of hearing loss and OAE should be considered as a standard screening procedure for all live births in our country.
Key words: OAE, TEOAE, DPOAE, ABR, hearing screening, hearing loss
Pro Otology 2-3: 115-118, 2003

INTRODUCTION

In recent years the measurement of OAE followed by ABR audiometry has provided an effective mean of identification of hearing impairement in neonatale period or soon after birth. It is very important for social, emotional and educational development of the deaf child and his or her family life. The earlier auditory stimulation is important also for the development of communicative and linguistic behaviour of the deaf child.

There are a lot of publications, where the autors discuss the results after the use of hearing aids, prescribed on children of age between 4 and 18 months. They illustrated that deaf infants could follow a normal path from communicative behaviour to spoken words. The early detection of hearing disorders in children is hightly recommended, because a primary disorder in the auditory periphery can produce secondery and irreversible disorders of auditory information processing. Investigations of Eggermont (1985/ have shown that the first weeks of life are e specially important for the full development of the auditory pathways.

In our country, we haven`t got a universal newborn hearing screening programme (Tzenev, 1999; Rouev, 2001a). In our clinic we use a battery of tests to examine the degree of hearing of the children. The majority of them come from the risk groups and only few of them are being examined, because of parents suspicion that their children have some hearing disorders. We use the factors defined by the Joint Committee on Infant Hearing (1991) about the risk newborn groups with sensoneural hearing loss:

1. Family history of congenital or delayed onset childhood sensorineural impairment.

2. Congenital infection known or suspected to be associated with sensorineural hearing impairment such as toxoplasmosis, syphilis, rubella, cyto-megalovirus and herpes.

3. Craniofacial anomalies including morphologic abnormalities of the pinna and ear canal, absent philtrum, low hairline, etc.

4. Birthweight less than 1500 g.

5. Hyperbilirubinaemia at a level exceeding indication for exchange transfusion.

6. Ototoxic medications including but not limited to the aminoglycosides used for more than five days (e.g., gentamicin, tobramicin, kanamicin, streptomicin) and loop diuretics used in combination with aminoglycosides.

7. Bacterial meningitis.

8. Severe depression at birth, which may include infants with Apgar scores of 0-3 at 5 min or those who fail to initiate spontaneous respiration by 10 min or those with hypotonia persisting to 2 h of age.

9. Prolonged mechanical ventilation for a duration equal to or greater than 10 days (e.g., persistent pulmonary hypertension).

10. Stigmata or other findings associated with a syndrome known to include sensorineural hearing loss (e.g., Waardenburg or Usher’s Syndrome).

There are a lot of children with mild and moderate sensoneural hearing loss, who come in our clinic after the age of 3.

The aim of our investigation is to answer the following questions, when we do the hearing examination:

- status of middle ears(is there a conductive hearing loss?);

- degree of hearing loss;

- configuration of hearing loss;

- type of hearing loss

- difference between the ears;

- site of lesion (sensoneural or neural).

METHODS

We use the following audiometric diagnostic methods to be able to answer higher questions:

- tympanometry and reflexometry;

- otoacoustic emissions – TEOAE and DPOAE;

- ABR with click stimulus;

- frequency specific ABR.

286 children of age between 0 to 36 mounts have been examined during the last 3 years. At first , we make the tympanometry to examine the status of the middle ear. If a middle year effusion is found, we stop the examination and continue when the middle ear is healthy.

The second step are OAEs (TEOAE or DPOAE). The clinical application of OAE is the detection of periferal auditory disfunction. The clinical measurment of EOAE is recognised as being objective, noninvasive and sensitive to peripheral auditory disfunction. They are repeatable, quickly recorded, frequency specific.

The most common clinical application of TEOAEs involves click stimuli presented at moderate intensities. The default employed by the ILO 88 equipment was selected to screen for hearing loss, if no response can be obtained, then it is likely that the patient has a hearing loss. Generally, the spectrum of a TEOAEs elicited from a healthy ear reflects the spectrum of the stimulus. TEOAEs obtained in response to the click stimuli are expected to have broad response spectra. The amplitudes of TEOAEs vary directly with the amplitudes of the stimuli, but the relation between stimulus and response are complicated by the fact that TEOAE`s result from a highly nonlinear phenomena. Under the default stimulus and recording conditions, the ILO 88 apparatus detects TEOAEs that are greater than 20 db SPL in newborns. Notmal TEOAE responses mirror the spectral properties of the stimulus used to elicit them. Clicks elicit broad spectrum responses that are most robust in the mid frequency region, probably owing to the fact that the middle ear transfer is most favorable in the region between 1000 and 3000 Hz. TEOAEs have contributed to the development of the understanding of how normal and disorded systems function and how they will likely adress problems of hearing impairement for long time.

For the detection of DPOAE we use a device from Grasson – Stadler. These commercial system is based on narrow band spectral analysis. For this device the f1 and f2 primary tones are digitally synthesized and presented to the ear canal either continuosly or as simultaneus long duration tone pulses. DPOAE is a function of the primary tone frequencies, because research findings indicate that 2f1 – f2 DPOAE is generated in the region of the cochlea that maximally responds to the primary tones and thus best reflects coclear status in this region. Current thinking concerns which frequency most accurately reflects the 2f1 – f2 generation site.The relation may be level – dependent, with lower - level tones best activating the frequency region to higher-level primaries optimally stimulating the geometric - mean region.

With the Brainstem Evoked Response Audiometry (BERA) we can evaluate the auditory pathways of the brainstem. With the electrodes placed on the patient`s scalp and on each earlobe, the changes and responses of brain waves to click acoustic stimuli are studied. Results from BERA can be paired. When the child isn`t profoundly deaf, we use a frequency specific ABR (only in the cases with mild and moderate hearing loss).

At last we prescribe the hearing aids independently of children age.

 

FIG 1. The "normal" OAE Screen.
 

FIG 2. The OAE Screen from child with hearing loss.

 

RESULTS

This study includes 286 children in the age of 0 to 36 months examined in our clinic.

The tympanometry has been normal by 194 children, but 92 patients needed some time to be under treatment for middle ear effusion and when the middle ear was healthy, we continiued the examination of this group of children.

The second step is TEOAE:

- by 68 children have a positive (normal) results ;

- by 218 children we can`t detect TEOAE.

All the children were examined with DPOAE also and the results are approximately the same:

- 70 children with normal screening test;

- 216 children need additonal hearing tests.

The third part of our examination is BERA (with click stimulus) and the results from 286 examineted children are the following:

- 70 children with normal hearing;

- 216 children with hearing disorders

- 52 children with mild and moderet hearing loss

- 164 children with severe or profound hearing loss.

After the examination and the determination of the degree and topic of hearing loss,we prescribed the hearing aids and prepared some of the children for cochlearimplantation.

About the children with mild and moderate hearing loss we do the frequency specific ABR.

 

FIG 3. The "normal" BERA Screen.
 

FIG 4. The BERA Screen from child with hearing loss.

 

CONCLUSION

1. The identification of hearing is late,especially by the children with mild and moderete hearing loss.

2. The majority of these children come from the risk groups.

3. OAE can be used as a first screening test for hearing impairement at the birth prior and is followed by an ABR testing. The baby is screened belaterally by using the OAE method just before leaving the hospital.

4. The children with mild and moderete hearing loss arrive in our clinic after the age of three, when they have the difficulties to develop speech, spoken language and achieve intelligibility problems.

The importance of the early screening is reflected by the fact, that hearing loss is one of the most common problems found in newborns. Once a hearing loss has been diagnosed and confirmed,counselling parents is critical to help them understand the nature and degree of their child`s hearing loss, describe the options for treatment and explain the implications of each option for the child`s communication development.

In 1998 The European Consensus Statement on Neonatal Hearing Screening was edited by F. Grandori and M. Lutman following a conference in Milano.

The first and the last point of this statement seem to be very important:

“ 1. Permanent childhood hearing impairment (PCHI) is a serious public health problem affecting at least one baby in one thousand. Intervention is considered to be most successful if commenced in the first few months of life. Therefore, identification by screening at or shortly after birth has the potential to improve quality of life and opportunities for those affected.”

Although the healthcare systems in Europe differ from country to country in terms of organisation and funding, implementation of neonatal hearing screening programmes should not be delayed. This will give new European citizens greater opportunities and better quality of life into the next millennium.”

Now in our country we are in process to intruduce the neonatal screening programme (P. Rouev et al., 2001b).

REFERENCES

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  5. Rouev P, Spiridonova J. Multi-stage protokol for implementation the universal newborn hearing screening. 7th National Congress of Otorhinolaryngology, Plovdiv, Bulgaria, Otorhinolaryngologia Suppl. 2001a: 65-72.

  6. Rouev P, Dimov P, Nikolov N et al. Universal Newborn Hearing Screening with ALGO-2(. 7th National Congress of Otorhinolaryngology, Plovdiv, Bulgaria, Otorhinolaryngologia Suppl. 2001b:73-80.

  7. Smith MF, Buffin JT. Click evoked otoacoustic emissions compared with brainstem electric response. Arch Dis Child 1989;64:1105-11.

  8. Stevens JC, Webb HD, Hutchinson J et al. Click evoked otoacoustic emissions in neonatal screening. Ear Hear 1990;11:128-33.

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