The UNHS is done within the first 3 months of life. It detects permanent hearing loss at an average age of 3 months. but in the absence of UNHS, the average age of diagnosis was found to be 31.25 months. Reliance on physician and parent’s observations was not found successful.
Behavioral methods of testing DO NOT meet the requirement of UNHS.
Currently, BRAINSTEM EVOKED RESPONSE AUDIOMETRY (BERA) and EVOKED OTOACOUSTIC EMISSIONS (EOAE) are employed either singly or in combination.
Interpretations of OAE —
The screening outcomes of OAE are either PASS or REFER:
- “Pass” infants need no further testing at this time but progressive, late-onset, and acquired hearing loss in childhood cannot be ruled out at this time.
- “Refer” infants require a diagnostic hearing evaluation. Electrocochleography measures auditory sensitivity to within 20 dB. It is an invasive procedure and avoided.
Auditory steady-state responses (ASSR) or the future development of frequency-specific auditory brain stem responses (aka ABR, BERA) will probably replace the current two-tiered screening protocol (OAE, ABR/ASSR).
EVALUATION OF UNIVERSAL NEWBORN HEARING SCREENING(UNHS) “REFER” INFANTS
The infants who fail UNHS should have a detailed history, and physical examination including ear microscopy and vestibular tests, threshold frequency-specific ABR and OAE, and visual reinforcement audiometry (VRA).
Newborn hearing screening does not identify progressive hearing loss, which does occur in preschool children and constitutes 15–20% of SNHL young children.
The ancillary testing includes laboratory and genetic testing, screening for maternally transmitted infections, and temporal bone imaging.
- Family history of congenital hearing loss, eye and cardiac abnormalities
- Prenatal maternal history of infection (TORCH and syphilis), diabetes, hypothyroidism, alcohol, smoking, and drugs
- Perinatal risk factors
A complete physical examination is mandatory though the majority of infants do not have any positive findings.
External and middle ear disorders are the most common source of failed initial hearing screening.
A thorough evaluation should include the following elements:
- Neurologic and developmental milestones
- Nystagmus: Spontaneous and head shaking
- External Auditory Canal (EAC): Clean it and see for stenosis and atresia
- Tympanic membrane for thickness, appearance, and motion and middle ear effusion (aka OME or Serous otitis Media or Glue Ear)
- Pneumatic otoscopy in older children: In 0–6 months of age, both tympanometry and pneumatic otoscopy can miss middle ear effusion. The incidence of middle ear effusion in the Ist year of life is quite high (61%).
Tympanostomy tube insertion is done for persistent middle ear effusion.
In infants of acute otitis media, antibiotic therapy is given with close follow-up for effusion resolution.
1) Frequency-specific ABR thresholds:
Both air and bone conductions are evaluated using tone-pip ABR. A significant air-bone gap indicates external and middle ear disorders.
2) Evoked otoacoustic emission
3) Tympanometry using a probe-tone frequency of 1,000 Hz or more:
Provide the status of the middle ear.
The traditional tympanometry (using 226 Hz probe tone) is invalid at 0–6 months of age.
4) Visual reinforcement audiometry (VRA)
Visual reinforcement audiometry is a form of conditioning technique. Infants turn their heads in the direction of the sound source.
If this response is rewarded by the activation of a lighted, animated toy, the infant usually continues to respond, and an audiogram is obtained.
OTHER HEARING TESTS
The auditory function tests in neonates, infants, and young children can be classified into various groups:
- Neonatal screening procedures: Arousal test, auditory response cradle, electric response audiometry
- Behavior observation audiometry:
It involves observing a change in an infant’s behavior in response to sound. Auditory signal produces a change in an infant’s behavior, such as alerting, cessation of activity, widening of eyes, and facial grimacing, which are seen as Moro’s reflex, Cessation reflex, Cochleopalpebral reflex, etc.
- Distraction techniques
- Conditioning techniques: Visual reorientation audiometry, play audiometry
- Objective tests: Evoked response audiometry, impedance audiometry, otoacoustic emissions, heart rate audiometry
## Though currently, the gold standards are ABR and OAE, the following tests were done traditionally.
1) Screening procedures:
These are based on the infant’s behavioral response to the sound signal.
- Arousal test: A high-frequency narrow band noise presented for 2 seconds to the light sleeping infant normally awakes the infant twice when three such stimuli are presented.
- Auditory response cradle: The baby is placed in a cradle. The transducers monitor the infant’s behavior (trunk and limb movement, head jerk, and respiration) in response to auditory stimulation.
- Behavior observation audiometry: Auditory signal produces a change in an infant’s behavior, such as alerting, cessation of activity, widening of eyes, and facial grimacing, which are seen as Moro’s reflex, Cessation reflex, Cochleopalpebral reflex, etc.
(a) Moro’s reflex: It consists of sudden movement of limbs and extension of the head in response to the sound of 80–90 dB.
(b) Cochleopalpebral reflex: A child blinks in response to a loud sound.
(c) Cessation reflex: In response to a sound of 90 dB, an infant stops activity or starts crying.
- Distraction techniques: The children of 6–7 months of age turn their heads to locate the source of the sound.
Method: The child is seated in the mother’s lap. One person distracts the child’s attention while the other produces a sound from behind or from one side. Note whether the child tries to locate the sound by turning the head.
Sounds used for distraction: They are high-frequency rattle (8 kHz), low-frequency hum, whispered sound as “S, S, S”, xylophone, warbled tones, or narrow band noise (500–4,000 Hz).
5) Conditioning techniques (play Aaudiometry): The child is conditioned to perform any act on hearing a sound. The acts may be placing a marble in a box, a wooden or plastic block in the bucket, or a ring on a post. The test can be done either in the free-field or by using headphones.
A frequency-specific audiogram is possible in a child of 2–4 years of age.
6) Speech audiometry: The spondee words are presented to the child along with the pictures. The child is asked to point the appropriate picture or repeat the word. The intensity level of the spondee words is gradually lowered. The speech reception threshold is determined. To examine the expressive ability, the child is asked to name the toys and objects.
2) Ancillary Laboratory Testing
They are ordered either to rule out or confirm specific etiologies suspected by hearing tests result, child’s age, history, physical examination, routine blood chemistry and complete blood count. For example, in cases of family history of episodes of syncope, ECG is taken to look for the evidence of Jervell and Lange-Nielsen syndrome.
3) Screening for Maternally Transmitted Infection (TORCH and Syphilis)
Infant’s blood for specific IgM for TORCH and syphilis.
Cultures for CMV in blood, urine or saliva: Detection in first 3 months of life and early treatment may lessen severity of neurologic sequelae.
FTA-ABS test for congenital syphilis
4) Genetic Testing
Chromosomal karyotyping is indicated when SNHL infant has:
- Unrecognizable constellation of anomalies
- Neurologic or cardiac defects
- Mother gives history of multiple miscarriages
- Suspected Pendred’s syndrome
- Screening for connexin 26 mutation: GJB2 gene encodes for connexin 26 and is said to be responsible for about 50% of all autosomal recessive congenital hearing loss.
35delG deletion: It involves a single base pair and is responsible for 70% of all connexin 26 mutations. The screening tests for 35delG deletion are available.
DFNB1 (prefix DFNB, signifies autosomal recessive hearing loss): It stands for autosomal recessive nonsyndromic hearing loss mutations in connexin 26 and is associated with prelingual nonprogressive bilateral SNHL (mild to profound) without temporal bone CT abnormality.
5) Temporal Bone Imaging
Noncontrast Temporal Bone CT:
- In all children with SNHL especially in progressive SNHL and craniofacial anomalies.
- The dilated vestibular aqueduct is associated with Pendred’s syndrome.
- Mondini dysplasia and semicircular canals abnormalities are also seen.
- Internal auditory canal stenosis and possible auditory nerve aplasia is associated with X-linked form of deafness (DFN3).
Magnetic Resonance Imaging:
It is done prior to cochlear implantation to assess the patency of the cochlea, position of the facial nerve, and presence of the auditory nerve.
Deaf and dumb: Deaf persons are not intellectually dumb. Psychological tests usually overlook the intellectual capacity of deaf people as they consist of culturally biased material.
Playgroups and parent groups facilitate parents to learn how to accommodate their baby’s communication needs.
The services of expert professionals who deal with childhood hearing loss and early childhood education are important.
It is essential to know not only the degree and type of hearing loss but also other associated handicaps, such as blindness or mental retardation.
The prelingual and postlingual hearing loss bears prognostic importance.
The broad groups of communication methodologies include —
American Sign Language (ASL),
Spoken and signed language, and
Aims of rehabilitation include the development of speech and language, adjustment in society, and useful vocational employment.
(A) Parental Guidance
Hearing loss happens not just to a child but the whole family. The parents should be sympathetically told of the child’s disability and how to care for it.
Parents should know the following requirements:
- Care and periodic replacement of hearing aid
- Change of ear moulds as the child grows
- Follow-up visits for reevaluation
- Education at home
- Selection of vocation
(B) Development of Speech and Language
Reception of information occurs through visual, auditory, or tactile faculties while expression is through the oral/written speech or manual sign language.
The proper communication needs either the improvement in hearing through amplification or the development of visual or tactile means of communication.
- Auditory-oral communication: This method of normal people’s communication can be used for children of postlingual deafness. Hearing aids augment auditory reception. Training is imparted in speech reading, which encourages attention towards the movements of lips, face, and natural gestures of hand and body.
Expressive skills should be encouraged through verbal speech.
- Manual communication: It uses sign language and finger-spelling methods.
The abstract ideas are difficult to express because the general public does not understand it.
(C) Total Communication
This form of communication, which is good for children with prelingual severe to profound deafness, employs all the sensory inputs such as auditory, visual, tactile and kinesthetic. These children are taught to develop oral speech, lip-reading and sign language.
- Vibrotactile aids: These are useful in children who are both deaf, as well as blind. The aids are fitted to the child’s hand or sternum. The vibrations of speech are perceived by the child through tactile sensation (Have you seen film “Black” of Amitabh and Rani Mukherji?).
(D) Education and Vocation of Deaf
- Residential and day schools for deaf children are available.
- Children with moderate hearing loss can be integrated into normal schools with preferential seating arrangements in the class
- In radio hearing aids, the microphone and transmitter are with the teacher and the receiver and amplifier are worn by the child. The child can hear the teacher’s voice better, avoiding the environmental noises.
- Given the opportunity commensurate with their ability, deaf people, who are sincere and good workers, can be usefully employed in several vocations.
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