Management of a deaf child

Management of a deaf child

1. MANAGEMENT OF A DEAF CHILD

2. Children with profound (>90dB loss) or total deafness fail to develop speech and have often been termed as deaf-mute or deaf dumb. the period of birth till 5 years of life is critical for the development of speech, therefore, there is need for early identification and assessment of hearing loss and early rehabilitation in infants and children

3. AETIOLOGY

4. GENETIC CAUSES Genetic disease results from abberations in coding function or processing of human DNA. Congenital SNHL is accounted for by genetic factors in half of the cases. About 77% of cases of hereditary hearing loss are autosomal recessive and 22% are autosomal dominant and 1% are X-linked. Approximately 30% of patients have syndromic hearing loss. Autosomal recessive non syndromic hearing loss is caused by mutations in GJB2 gene ( codes for protien connexin 26) and GJB6 gene (codes for connexin 30).

5. NON – GENETIC CAUSES PRENATAL CAUSES PERINATAL CAUSES POSTNATAL CAUSES Before Birth Includes: Infant factors Maternal factors During birth Includes causes during birth or early neonatal period. After birth Includes genetic and non genetic factors

6. PRENATAL CAUSES INFANT FACTORS An infant may be born with inner ear anomalies due to genetic or non genetic causes and these anomalies may be syndromic or non syndromic . The anomalies affecting inner ear may involve only membranous or both membranous and bony labyrinth. They include :

7. SCHEIBE’S DYSPLASIA : It is the most common inner ear anomaly. Bony labyrinth is normal and superior part of membranous labyrinth ( utricle and semicircular ducts ) is also normal. Dysplasia is seen in cochlea and saccule i.e. why called cochleosaccular dysplasia. It is inherited as autosomal recessive nonsyndromic trait. ALEXANDER DYSPLASIA : Affects only the basal turn of membranous cochlea. Only high frequencies are affected , residual hearing present in low frequencies BING-SIEBERMANN DYSPLASIA : Complete absence of membranous labyrinth. MICHEL DYSPLASIA : Complete absence of bony and membranous labyrinth. Even the petrous apex is absent but middle and external ear may be completely normal.

8. MONDINI DYSPLASIA : Only basal coil is present or cochlea is 1.5 turns. There is incomplete partition between scalae due to absence of osseous spiral lamina. Maybe unilateral or bilateral. The deformity maybe seen in Pendred , Waaredenburg , branchio- oto -renal, Treacher - Collins syndrome and wildervanck syndrome. ENLARGED VESTIBULAR AQUEDUCT : Vestibular aqueduct is enlarged >2mm, endolymphatic sac is also enlarged and can be seen on t2 MRI. It causes early onset SNHL which is progressive and vertigo may be present and perilymphatic fistula may occur . SEMICIRCULAR CANAL MALFORMATIONS: Both superior and lateral or only lateral semicircular canal malformations may be seen.

9. MATERNAL FACTORS Infections during pregnancy : Include toxoplasmosis, rubella, cytomegalovirus, herpes type1 and 2 and syphilis. Drugs during pregnancy Include streptomycin, gentamicin, amikacin , quinine or chloroquine . They cross the placental barrier and damage fetal cochlea. Radiation to mother in first trimester Other factors : Nutritional deficiencies, diabetes, toxemia, thyroid deficiency and maternal alcoholism.

10. PERINATAL FACTORS ANOXIA : It damages cochlear nuclei and causes haemorrhage into the ear. Placenta praevia , prolonged labour , cord arpund the neck amd prolapsed cord can acuse fetal anoxia. PREMATURITY AND LOW BIRTH WEIGHT BIRTH INJURIES : Due to forceps delivery. May cause intracranial haemorrhage with extravasation of blood into inner ear. NEONATAL JAUNDICE : Bilirubin levels greater than 20% damages the cochlear nucleus. NEONATAL MENINGITIS SEPSIS OTOTOXIC DRUGS

11. Viral infections ( measles, mumps, varicella, influenza, meningitis, encephalitis) Secretory otitis media Ototoxic drugs Trauma eg . fractures of temporal bone, middle ear surgery, perilymph leak. Noise induced deafness ACQUIRED CAUSES

12. MENINGITIS : Most common cause of permanent childhood hearing impairment. Risk of getting PCHI is 10% after bacterial meningitis Early cochlear implantation is necessary as delay can cause cochlear ossification and makes implantation difficult. MEASLES : Highly infectious viral illness, reported as major aetiological agent for severe profound bilateral hearing loss in children, mostly after 6 months of age. Observed hearing loss can be conductive and is attributable to supprative otitis media, chronic perforation and mastioiditis but mostly deafness is sensorineural . MUMPS : Very rare but unilateral SNHL if present.

13. EVALUATION OF A DEAF CHILD FINDING THE CAUSE: SUSPICION OF HEARING LOSS: Hearing loss is to be suspected if : The child sleeps through loud noises undisturbed or fails to startle to loud sounds. Fails to develop speech at 1-2 years A partially hearing child may have a defective speech and perform poorly at school.

14. RISK FACTORS FOR HEARING LOSS IN CHILDREN: Family history of hearing loss Prenatal infections Craniofacial abnormalities including those of pinna and ear canal Birth weight less than 1500g Hyperbilirubinemia requiring exchange transfusion Ototoxic medications included but not limited to aminoglycosides used in multiple courses or in combination with loop diuretics. Bacterial meningitis APGAR score 0-4 in 1 min or 0-6 in 5 min. Mechanical ventilation for 5 days or more Syndromic findings associated with hearing loss

15. ASSESMENT OF HEARING IN INFANTS AND CHILDREN

16. SCREENING TESTS They are employed to test hearing in high risk infants and are based on infants behavioral response to sound signal. Right now we have a universal neonatal screening programme for early detection. Tests used are : otoacoustic emmisions (OAE) and auditory brainstem response (ABR). OAEs are generated at the outer hair cells and can be picked up from the external ear as the energy produced by them travels in reverse direction from outer hair cells to ossicles , then TM and to the ear canal, from where it is picked up. OAEs are absent if outer hair cells are not functional or there is middle ear effusion or canal debris due to meconium.

17. ABRs are generated in response to sound stimulus presented to the ear and picked up from the scalp. With a response of 30-35 dB normal HL, the infant who passes the test and the hearing is considered normal. Infants who fail these tests are followed up with repeat tests AROUSAL TEST : a high frequency narrow band noise is presented for 2 seconds to the infant when he is in light sleep. A normal hearing infant can be aroused twice when three such stimuli are presented to him. AUDITORY RESPONSE CRADLE: it is a screening device for newborns where the baby is kept in a cradle and his behavior ( trunk and limb movements, head jerk and respiration) in response to auditory stimulation.

18. BEHAVIOUR OBSERVATION AUDIOMETRY MORO’S REFLEX CESSATION REFLEX COCHLEOPALPEBRAL REFLEX Sudden movement of limbs and extension of head in response to sound of 80-90 dB An infant stops activity or starts crying in response to sound of 90dB Child responds by a blink to a loud sound.

19. DISTRATCTION TECHNIQUES Used in children 6-7 months old. The child at this age turns head to locate source of sound. In this test, the child is seated in mother’s lap, an assistant distracts the child’s attention while the examiner produces a sound from behind or from one side to see if child tries to locate it. Sounds used are high frequency rattle (8kHz), low frequency hums, whispered sounds, xylophone, warbled notes or narrow band noise (500-4000Hz)

20. CONDITIONING TECHNIQUES VISUAL REINFORCEMENT AUDIOMETRY PLAY AUDIOMETRY SPEECH AUDIOMETRY It is a conditioning technique in which the child is trained to look for auditory stimulus by turning his head. This test helps to determine the hearing threshold. Child is conditioned to perform an act such as placing a marble in a box, putting a ring on a post or putting a plastic block in a bucket each time he hears a sound signal. each correct performance is reinforced by praise, encouragement or reward. Child is asked to repeat names of certain objects or to point them out on pictures. The voice can be gradually lowered. In this speech discrimination and hearing level can be tested and also child’s expressive ability can be examined.

21. OBJECTIVE TESTS EVOKED RESPONSE AUDIOMETRY:

22. OTOACOUSTIC EMISSIONS : Transient evoked emissions are absent in ears where the hearing loss exceeds 30dB. Distortion product emissions are absent when hearing loss exceeds 50dB. IMPEDANCE AUDIOMETRY : Normally, stapedius muscle contracts reflexly in response to sound of 70-100dB. And this reflex can be recorded. Absence indicates middle ear disorder, retrocochlear hearing loss or severe SNHL.

23. SINGLE SIDED DEAFNESS: Screening helps in early detection of unilateral sensorinueral hearing loss. Previously, unilateral hearing loss was considered of little significance as speech and language developed appropriately unilateral hearing loss results in an inability to hear from the direction of deaf side, difficulty in hearing speech in noise and poor localization of sound. children with unilateral hearing loss appear to have increased rates of grade failures, need educational assistance and may show behavioral issues in classroom.

24. INVESTIGATIONS CLINICAL EXAMINATION : All children with hearing loss of unknown cause should be evaluated for features associated with syndromic deafness. Important features include branchial cleft pits, cysts or fistulae, preauricular pits, telecanthus , heterochromia iridis , white forelock, pigmentary anomalies, high myopia, pigmentary retinopathy, goitre , craniofacial abnormalities. AUDIOLOGY: Skilled audiological testing is performed to assess the severity of hearing loss.

25. IMAGING : Imaging can detect treatable pathologies such as perilymph fistula, inner ear malformations with an associated risk of meningitis and the enlarged vestibular aqueduct. Both CT and MRI can be useful. On CT scans,a large vestibular aqueduct is most common finding , while cochlear dysplasia is most common abnormality in scans showing multiple abnormalities. Other abnormal findings include lateral SCC dysplasia, otic capsular lucency , small internal auditory canals and hypolastic cochlea. MRI scans are more likely to detect abnormalities with increasing severity of hearing loss and a significantly higher imaging yield with unilateral SNHL than with bilateral.

26. MANAGEMENT PARENTAL GUIDANCE HEARING AIDS COCHLEAR IMPLANTS SPEECH AND LANGUAGE THERAPY EDUCATION OF THE DEAF VOCATIONAL GUIDANCE