Evaluation of deaf child

Evaluation of Deaf Child. Early screening and assessment of hearing loss are vital for infants and children. Early identification can help to make early decisions about hearing rehabilitation including hearing aids, and cochlear implants. From birth to 5 years of age, the child develops speech and language. The child managed before 6 months of age develops good vocabulary and better expressive and comprehensive language skills. Therefore early identification of a child’s hearing impairment is important. Screening and surveillance is the most effective and cost-effective ways to identify congenital hearing loss.

Definition of Deaf child. Children with profound (> 90 dB loss) or total deafness who fail to develop speech are termed deaf-mute or deaf and dumb.

Aetiology. The onset of hearing loss may be before birth (prenatal), during birth (perinatal) or afterbirth (postnatal).

A. Prenatal causes. They may pertain to the infant or the mother.

1. Genetic defects in infants. An infant may be born with inner ear anomalies due to genetic or nongenetic causes. Anomalies may affect the inner ear only, both the membranous and bony labyrinths or involve only the membranous labyrinth (non-syndromic) or can be part of a syndrome (syndromic). It results in various forms of malformations. They include:

Anomalies Affecting Both Bony and Membranous Labyrinths:

• Mondini dysplasia. There is dysplasia of the bony and membranous labyrinth. It usually occurs bilaterally but unilateral is also seen. This deformity may be seen in isolation or in association with syndromes like Enlarged vestibular aqueduct, Pendred, Klippel-feil, Waardenburg and Treacher-Collins. Anomalies of Cochlea usually seen are:

• • There may be only 1.5 cochlear turns present instead of 2.5 turns.
  • Basal coil is only present.
  • Absence of osseous spiral lamina leading to incomplete partition between the scalae.
  • Absence of modiolus.

• Michel aplasia. There is total aplasia of bony and membranous labyrinth. The petrous apex is also absent. Despite normal external and middle ears, hearing aids or cochlear implants are not viable options due to the lack of inner ear development.

• Common cavity: There is no division between cochlear and vestibular parts. Instead, a single cavity is present. This malformation results in significant hearing impairment.

Anomalies Primarily Affecting the Membranous Labyrinth: These anomalies spare the bony labyrinth and primarily involve the membranous labyrinth:

• Scheibe dysplasia. This is one of the most common inner ear deformities in deaf children. It is inherited as an autosomal recessive non-syndromic condition. The bony labyrinth and the upper part of the membranous labyrinth (utricle and semicircular ducts) remain normal. Anomalies usually seen are:

• • Marked dysplasia is seen in the membranous cochlea and saccule; hence also called as cochleosaccular dysplasia.
  • Hypoplastic cochlear nerve and inferior division of vestibular nerve is seen.
  • Organ of corti may be absent.

• Alexander dysplasia. Basal turn of the membranous cochlea is affected causing high-frequency hearing loss. Hearing can be improved by use of hearing aids, as lower frequencies are still preserved.
• Bing-Siebenmann dysplasia. This rare condition involves a complete absence or dysplasia of the membranous vestibular labyrinth, while the cochlea remains normal.

Specific Isolated Anomalies: These are distinct malformations with specific presentations:

• Enlarged vestibular aqueduct. There is an enlargement of the vestibular aqueduct (greater than 2 mm) and the endolymphatic sac, which can be identified through T2 MRI imaging. It causes early-onset progressive sensorineural hearing loss during childhood. Attacks of vertigo may be present. A perilymph fistula may also be seen.
• Cochlear/ vestibular nerve aplasia or malformation. This involves the absence or malformation of the cochlear or vestibular nerves, leading to profound hearing loss and impaired balance.
• Semicircular canal malformations. Malformations are related to superior and lateral semi-circular canals, impairing balance and coordination.

Mnemonic to Remember the Anomalies: “My Son Can Study Amazing Biology Concepts Every Class” (M – Mondini Dysplasia, S – Scheibe Dysplasia, C – Common Cavity, S – Semicircular Canal Malformations, A – Alexander Dysplasia, B – Bing-Siebenmann Dysplasia, C – Cochlear/Vestibular Nerve Aplasia, E – Enlarged Vestibular Aqueduct, C – Michel Aplasia).

2. Maternal factors. Factors affecting developing foetus during pregnancy.

• Infections. Toxoplasmosis, rubella, cytomegaloviruses, herpes type 1 and 2 and syphilis. Remember the mnemonic, TORCHES.
• Drugs. Streptomycin, gentamicin, tobramycin, amikacin, thalidomide, quinine or chloroquine.
• Radiation during the first trimester.
• Other factors. Nutritional deficiency, Alcohol intake, diabetes, toxaemia and thyroid deficiency.

B. Perinatal Causes. Perinatal causes occur during birth or the early neonatal period and can significantly impact the auditory system. Key causes include:

1. Anoxia causes damage to the cochlear nuclei and leads to haemorrhage in the ear. Common risk factors include placenta previa, prolonged labour and umbilical cord complications (cord around the neck or prolapsed cord), leading to fetal anoxia.
2. Prematurity and Low Birth Weight. Babies born before term or with a birth weight less than 1,500 g (3.3 lb) are at a higher risk of auditory damage due to underdeveloped systems.
3. Birth Injuries. Birth injuries such as those caused by forceps delivery can lead to intracranial haemorrhage, with blood extravasation into the inner ear, affecting hearing.
4. Neonatal Jaundice. Bilirubin levels exceeding 20 mg% can damage the cochlear nuclei, leading to sensorineural hearing loss.
5. Neonatal Meningitis and Sepsis. These infections can severely damage the auditory system, leading to hearing loss.
6. Time Spent in Neonatal ICU. Prolonged stays in the neonatal intensive care unit (NICU) often expose infants to risk factors like infections, mechanical ventilation, and ototoxic medications.
7. Ototoxic Drugs. Drugs used to treat neonatal meningitis or septicemia, such as aminoglycosides, can damage the inner ear, causing irreversible hearing loss.

C. Postnatal Causes. Postnatal causes occur after birth and can be categorized into genetic and non-genetic origins:

1. Genetic Causes. Genetic factors contribute to familial progressive sensorineural deafness or syndromes like Alport Syndrome, Klippel-Feil Syndrome, and Hurler Syndrome. Though genetic, these conditions may manifest later in childhood or adulthood.
2. Non-Genetic Causes. Postnatal non-genetic causes are similar to those in adults but often have distinct characteristics in children:

• Viral Infections. Infections such as measles, mumps, varicella, and influenza can damage the cochlear structures, leading to hearing loss.
• Meningitis and Encephalitis. These infections can cause inflammation and damage to the auditory nerves or pathways, resulting in hearing loss.
• Secretory Otitis Media. Chronic middle ear infections can lead to conductive or sensorineural hearing loss if untreated.
• Ototoxic Drugs. Medications such as aminoglycosides and chemotherapeutic agents used postnatally can cause auditory damage.
• Trauma, including temporal bone fractures, middle ear surgery, or perilymphatic fistulas, can lead to hearing impairment.
• Noise-Induced Hearing Loss. Exposure to loud sounds during childhood or adolescence can cause permanent damage to the hair cells in the cochlea.
• Neonatal Jaundice and Meningitis. Unresolved neonatal jaundice and meningitis remain significant contributors to sensorineural hearing loss even postnatally.

Evaluation of a deaf child. Early diagnosis and management are crucial to prevent delays in speech and language development. The evaluation of a deaf child requires a systematic approach to identify the underlying cause of hearing loss.

1. Comprehensive history taking. A detailed history of prenatal, perinatal or postnatal period is the foundation for determining the cause of hearing loss.

• Any complications in pregnancy, delivery or the postnatal period
• Assess developmental milestones including speech and language and motor to identify delays.
• Noise exposure.
• Ototoxic medications.
• Head injuries.
• Infections. Ear disease, meningitis and viral illness
• Immunization status
• Detailed Family history.  Hearing loss and other risk factors associated with hearing loss.

2. Risk factors for permanent congenital hearing loss are:

• Child kept in neonatal intensive care unit (NICU) for more than 48 hours.
• Family history of early childhood deafness.
• Craniofacial anomaly (e.g. cleft palate) associated with hearing impairment.
• Prenatal infections (TORCHES).
• Birth weight below 1500 g (3.3 lbs).
• Ototoxic medications
• Bacterial meningitis
• Hyperbilirubinemia (severe jaundice).
• Apgar score of 0–4 at 1 min or 0–6 at 5 min.

3. Recognizing suspicion of hearing loss. Hearing loss is suspected if (i) the child sleeps unperturbed or does not respond or startle to loud sounds, (ii) fails to develop speech at 1–2 years, (iii) Defective speech, poor school performance, or being mislabelled as mentally retarded. A partially hearing child may have a defective speech and perform poorly in school and be labelled mentally retarded. Children with any of the above symptoms or risk factors must undergo screening and regular follow-up to ensure timely intervention.
4. Physical examination. Inspection of any craniofacial anomalies, palatal abnormalities, branchial cysts, sinuses. Inspect for heterochromia iridis (different-coloured eyes), white forelock or fistulae that may indicate syndromic conditions.
5. Hearing tests. They should be age-appropriate to assess the level and type of hearing loss.
6. Radiological Investigations. Magnetic resonance imaging of inner ears and/or computed tomography of petrous temporal bones.

Methods of hearing assessment in infants and children

Effective hearing assessment in infants and children relies on the appropriate choice of test, considering the child’s age and cooperation level.

1. Screening Procedures. (Key developmental age: 0–6 months, up to adult if appropriate). Screening tests are used to identify hearing loss in high-risk infants, based on their behavioural responses to sound. It has been found that 95% of children with risk factors have normal hearing, while 50% of children with sensorineural hearing loss have no risk factors. This highlights the importance of universal neonatal screening for early hearing detection. OAE and BERA are key electrophysiological objective tests for early identification of hearing loss in infants under 6 months, who cannot cooperate. These tests are also useful for children or adults with special needs who are unable to cooperate. OAE is quick and cost-effective, while BERA provides more accurate results but is more time-consuming. Other methods, like the arousal test and ARC, offer additional screening options.

A. Otoacoustic Emissions (OAE). OAEs are low-intensity sound signals produced by the outer hair cells of the cochlea, which are recorded through a microphone in the external ear canal. The signals travel in reverse direction from outer hair cells→ basilar membrane → perilymph → oval window  → ossicles → tympanic membrane → external ear canal. OAEs detect outer hair cell dysfunction earlier than a pure tone audiogram. OAEs are present when

• Outer hair cells are normal and healthy.
• VIIIth nerve lesion as cochlear hair cells are normal thus helps to test the function of VIIIth nerve.

OAE’s are absent when.

• Outer hair cells are damaged or non-functional thus helping to test the function of cochlea.
• Hearing loss more than 30 dB.
• In 50% of normal individuals.
• Lesions of cochlea.
• Middle ear disorders i.e. effusion, as sound signals coming back cannot be picked up by the microphone.
• Debris in the outer ear.

To read more about Otoacoustic emissions, click on the link: https://www.entlecture.com/otoacoustic-emissions/

B. Brainstem Evoked Response Audiometry (BERA). It assesses the integrity and function of the central auditory pathway, including the VIIIth nerve, pons, and midbrain. It records electrical potentials generated by the auditory system in response to sound stimuli (clicks or tone bursts), measured via surface electrodes on the scalp. It may require sedation in children. To measure the hearing threshold in an infant, ABR tracing is obtained first at the higher sound stimulus and then gradually lowered till wave V is just identifiable but repeatable. If an infant fails the BERA twice, further assessment is recommended. Indications for BERA in screening.

• Child who fails the OAEs test on two occasions.
• Child kept in the neonatal intensive care unit, and both OAEs and BERA are performed.

Interpretations.

• ABR waves are usually absent when a patient has severe or profound hearing loss.
• Identifiable waveforms are generally seen 10–20 dB above the behavioural threshold.
• Hearing is regarded as normal with a response of 30–35 dB nHL.

To read more about BERA, click on the link: https://www.entlecture.com/bera/

C. Arousal test. Method. When the infant is in light sleep. A narrow band noise of high frequency is delivered three times for 2 seconds. Interpretation. Infants having normal hearing will get aroused a minimum of two times.

D. Auditory response cradle (ARC) is a fully automated screening device for newborns. In this test, the infant is placed in a cradle and his behavioural responses (head jerk or turn, body movements, and respiration) in response to sound stimulus (high pass noise). The responses are monitored by transducers. The transducer is a polyethylene band placed around the infant’s abdomen. ARC is a useful test for screening moderate, severe or profound hearing loss in babies.

2. Behaviour Observation Audiometry. (Key developmental age: 0–6 months) 

The idea is to check behavioural responses to sound stimuli delivered to an infant. The responses can be alteration in sucking response, alerting, cessation of activity, widening of eyes or facial grimacing. Although BOA is not preferred over electrophysiological tests. But may be of particular value in infants having auditory neuropathy spectrum disorder when ABR is a poor indicator of functional hearing levels. 

• Moro’s reflex is a reflex reaction of infants in response to a sound of 80–90 dB. It is characterized by sudden extension of arms and legs away from the body and then drawing back. Extension of head in also present. 
• Cochleo-palpebral reflex, there is contraction of the orbicularis muscle causing blinking of the eye in response to loud sound. 
• Cessation reflex, In response to a sound of 90 dB, an infant stops activity or starts crying.

3. Distraction Test. (Key developmental age: 06-18 months). The test incorporates the principle that young children at this age turn their head to locate the source of auditory stimulus. In this test, the child sits on the parent’s lap or on an infant seat. The child is lightly distracted by an assistant sitting directly in front who holds their attention. While the examiner produces a sound for <2 seconds. Sounds used are calibrated narrow-band noise (500–4000 Hz), high-frequency rattle (8 kHz), low-frequency hum, warble tones or ling sounds, whispered sounds such as “S, S, S”, and xylophone. The sound is delivered from a distance of 15 cm and should be out of the peripheral vision of the child. or delivered via insert earphones. Both the distractor and examiner can observe the response.

4. Conditioning tests.

• Visual reinforcement audiometry (VRA). Key developmental age: 5-36 months. It is a conditioning technique in which child is trained to look for visual stimulus in response to a sound stimulus by turning his head. This behaviour is reinforced by a flashing light or an animated toy. It is commonly used test battery for hearing assessment in preschool children. This test uses standard audiometric methods to determine the hearing threshold. The sound is delivered by headphones or earphones. 
• Play audiometry. Key developmental age: 2–5 years. The test follows principle that the child is conditioned to wait for a sound signal and then to respond by performing a specific task. Simple tasks which involve a simple repetitive activity such as placing a toy in a box, putting a ring on a stick or putting balls in a bucket each time when the child hears a sound signal. Hearing thresholds can be determined by 10dB down, 5dB-up/ descending-ascending technique as described for pure tone audiometry. Each correct response is reinforced with vocal praise, clapping or reward. 
• Speech audiometry. In a quiet room, using live voice, the child is asked to repeat the names of toys or point pictures placed on a table. The live voice level is gradually lowered. In this way, hearing thresholds and speech discrimination thresholds or scores are recorded. A child with normal hearing is expected to repeat 80% of the names of toys or point pictures at ≤40dB(A). The ability of a child to discriminate speech signals is an important measure of functional hearing with normal to moderate degrees of hearing loss. 
• The cooperative test. (Key developmental age: 18–30 months) It is a valuable alternative test where equipment and facilities are limited. The child is asked to discriminate three different simple instructions, for instance having been handed a small toy, asked to ‘give it to Mummy’ or ‘give it to daddy’ or ‘give it to baby’. Starting at a supra-threshold level, the voice is then dropped. A child with normal hearing may discriminate the instruction at 35–40dB(A). 

5. Pure tone audiometry. (Key developmental age: 3 years onwards) If the child is conditioned adequately to the PTA test. Using play audiometry technique it is often possible to measure hearing thresholds through PTA close to adult levels.

6. Objective tests

A. Evoked Response Audiometry.

• Electrocochleography (ECoG). It identifies hearing thresholds within a 5–10 dB range, making it suitable for young infants and children. ECoG detects electrical activity in the outer hair cells of the cochlea, including cochlear microphonic potentials, summating potentials, and auditory nerve action potentials. It provides precise auditory sensitivity measurement between 1000 and 8000 Hz without requiring masking of the contralateral ear. However, the invasiveness limits its frequent use.
• Auditory Brainstem Response (ABR). ABR evaluates auditory thresholds by analyzing identifiable waveforms, especially wave V, which correlates closely with behavioural pure-tone thresholds. In screening, a response to click stimuli at ≤40 dB nHL indicates normal hearing. For diagnostic purposes, thresholds are determined by reducing sound intensity until wave V is just identifiable.

B. Otoacoustic Emissions (OAEs). OAEs measure cochlear function and are commonly used in newborn hearing screenings. Transient Evoked OAEs (TEOAEs): Absent when hearing loss exceeds 30 dB. Distortion Product OAEs (DPOAEs): Absent when hearing loss exceeds 50 dB.

C. Impedance audiometry.It is based on the fact that a loud sound 70–100 dB above the hearing threshold of one ear, causes bilateral contraction of the stapedius muscle (which pulls the stapes slightly outward and upward) & and tensor tympani muscle (pulls the tympanic membrane slightly inward). The effect is more pronounced on the stapedius muscle than on tensor tympani. The absence of acoustic reflex indicates middle ear disorder, retrocochlear hearing loss or severe to profound SNHL. It differentiates cochlear and retro-cochlear pathology. In cochlear lesions,the stapedial reflex is present at lower intensities, e.g. 40–60 dB than the usual 70 dB(recruitment phenomenon). Absence of acoustic reflex but an abnormal tympanogram generally indicates conductive loss. The absence of acoustic reflex, but a normal tympanometry with parental concern for hearing loss suggests the possibility of SNHL of severe to profound degree. Since ABR and OAEs provide more information, the use of acoustic reflexes in the assessment of paediatric testing is not done commonly.

Download full PDF Link:
Evaluation of deaf child Dr Rahul Bagla ENT Textbook

———— End of the chapter ————

Reference Textbooks.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Glasscock-Shambaugh, Textbook of Surgery of the Ear.
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
• Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
• Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery
• Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
• Salah Mansour, Middle Ear Diseases – Advances in Diagnosis and Management.
• Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
• Rob and smith, Textbook of Operative surgery.
• Anirban Biswas, Textbook of Clinical Audio-vestibulometry.
• Arnold, U. Ganzer, Textbook of  Otorhinolaryngology, Head and Neck Surgery.

Author:

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
India

———– Follow us on social media ————

• Follow our Facebook page: https://www.facebook.com/Dr.Rahul.Bagla.UCMS
• Follow our Instagram page: https://www.instagram.com/dr.rahulbagla/
• Subscribe to our Youtube channel: https://www.youtube.com/@Drrahulbagla
• Please read. Anatomy of External Ear. https://www.entlecture.com/anatomy-of-ear/
• Please read. Anatomy of Temporal Bone. https://www.entlecture.com/anatomy-of-temporal-bone/
• Please read. Stenger’s, Chimani Moos, Teal test. https://www.entlecture.com/special-tuning-fork-tests/