HISTORY TAKING, INVESTIGATION AND PRE OP.pptx

History taking, investigation and pre op work up of deaf child

1. HISTORY TAKING, INVESTIGATION AND PRE OP WORK UP OF DEAF CHILD AND COCHLEAR IMPLANT DR. AKASHKUMAR RAMANI

2. OUTLINE INTRODUCTION ETIOLOGY OF HEARING LOSS HISTORY TAKING INVESTIGATION COCHLEAR IMPLANT

3. INTRODUCTION Children with profound (>90 dB loss) or total deafness fail to develop speech and have often been termed deaf-mute or deaf and dumb. children have no defect in their speech producing apparatus but the main defect is deafness that’s why They have never heard speech and therefore do not develop it and in lesser degrees of hearing loss, speech does develop but is defective.

4. The period from birth to 5 years of life is critical for the development of speech and language, therefore, there is need for early identification and assessment of hearing loss and early rehabilitation in infants and children. It was observed that children whose hearing loss was observed and managed before 6 months of age had higher scores of vocabulary, better expressive and comprehensive language skills than those diagnosed and managed after 6 months of age emphasizing the importance of early identification and treatment.

5. ETIOLOGY OF HEARING LOSS PRENATAL CAUSE A) INFANT FACTOR B) MATERNAL FACTOR PERINATAL CAUSES POSTNATAL CASUES A) GENETIC B) NON GENETIC

6. PRENATAL CAUSE INFANT FACTOR An infant may be born with inner ear anomalies due to genetic or nongenetic causes. Anomalies may affect inner ear alone (non syndromic) or may form part of a syndrome (syndromic). Anomalies affecting the inner ear may involve only the membranous labyrinth or both the membranous and bony labyrinths.

7. Scheibe dysplasia. It is the most common inner ear anomaly. Bony labyrinth is normal. Superior part of membranous labyrinth (utricle and semicircular ducts) is also normal. Dysplasia is seen in the cochlea and saccule; hence also called cochleosaccular dysplasia. Alexander dysplasia. It affects only the basal turn of membranous cochlea. Thus only high frequencies are affected. Residual hearing is present in low frequencies and can be exploited by amplification with hearing aids.

8. Bing- Siebenmann dysplasia. There is complete absence of membranous labyrinth. Michel aplasia. There is complete absence of bony and membranous labyrinth. Even the petrous apex is absent but external and middle ears may be completely unaffected. No hearing aids or cochlear implantation can be used.

9. MONDINI DYSPLASIA. Only basal coil is present or cochlea is 1.5 turns. There is incomplete partition between the scalae due to absence of osseous spiral lamina. Condition is unilateral or bilateral.

10. ENLARGED VESTIBULAR AQUEDUCT. Vestibular aqueduct is enlarged (>2 mm), endolymphatic sac is also enlarged and can be seen on T2 MRI. It causes early onset sensorineural hearing loss which is progressive. Vertigo may be present. Perilymphatic fistula may occur.

11. SEMICIRCULAR CANAL MALFORMATIONS. Both superior and lateral or only lateral semi circular canal malformations may be seen. They can be identified on imaging techniques.

12. MATERNAL FACTORS Infections during pregnancy . Infections which affect the developing fetus are toxoplasmosis, rubella, cytomegaloviruses, herpes type 1 and 2 and syphilis. Remember mnemonic, TORCHES. Drugs during pregnancy. Streptomycin, gentamicin, tobramycin, amikacin, quinine or chloroquine, when given to the pregnant mother, cross the placental barrier and damage the cochlea. Thalidomide not only affects ear but also causes abnormalities of limbs, heart, face, lip and palate

13. Radiation to mother in the first trimester. Other factors Nutritional deficiency, diabetes, toxaemia and thyroid deficiency. Maternal alcoholism is also teratogenic to the developing auditory system.

14. PERINATAL FACTOR They relate to causes during birth or in early neonatal period. ANOXIA. It damages the cochlear nuclei and causes haemorrhage into the ear. Placenta praevia, prolonged labour, cord round the neck and prolapsed cord can all cause fetal anoxia. PREMATURITY AND Low BIRTH WEIGHT. Born before term or with birth weight less than 1500 g (3.3 lb). BIRTH INJURIES. e.g. forceps delivery. They may cause intracranial haemorrhage with extravasation of blood into the inner ear.

15. Neonatal Jaundice. Bilirubin level greater than 20 mg% damages the cochlear nuclei. Neonatal Meningitis Sepsis Time Spent in Neonatal ICU  Ototoxic Drugs. used for neonatal meningitis or septicaemia.

16. POST NATAL CAUSE GENETIC. Though deafness is genetic, it manifests later in childhood or adult life. Deafness may occur alone as in familial progressive sensorineural deafness or in association with certain syndromes. NONGENETIC. They are essentially same as in adults and include: (a) Viral infections (measles, mumps, varicella, influenza),meningitis and encephalitis. (b) Secretory otitis media. (c) Ototoxic drugs. (d) Trauma, e.g. fractures of temporal bone, middle ear surgery or perilymph leak. (e) Noise-induced deafness.

17. HISTORY TAKING A thorough history taking is essential part of assessing the child suspected to be deaf. A proper history will be able to give us an etiological diagnosis in most cases. Relevant questions like, Is there any family history of congenital or delayed onset childhood deafness? Is there any history of mother having germen measles, herpes, syphilis, toxoplasmosis, etc during early part of pregnancy?

18. Is there birth weight is less then 1.5kg ? Is there history of taking ototoxic drugs like gentamycin, tobramycin, kanamycin, antimalarials and diuretics like furosemide of mother during the pregnancy or the child immediately after the birth ? Is there is history of low APGAR score of 0-3 at 5 minutes of child ? Is there is history of prolonged assisted ventilation period ? Ask about the proper history of the milestones of development.

19. INVESTIGATIONS Neonatal screening procedures OAEs Auditory brainstem response. Arousal test Auditory response cradle Behaviour observation audiometry Moro’s reflex Cochleopalpebral reflex Cessation reflex Distraction techniques (6–18 months) Conditioning techniques (7 months – 2 years) Visual reinforcement audiometry Play audiometry (2–5 years) Speech audiometry. Objective tests Evoked response audiometry. 1) Auditory Brainstem Response . 2) Electrocochleography Otoacoustic emissions Impedance audiometry

20. NEONATAL SCREENING PROCEDURES They are employed to test hearing in “high-risk” infants and are based on infant’s behavioural response to the sound signal. It is now observed that 95% of children with one or more risk factors have normal hearing. On the contrary, 50% of children with sensorineural hearing loss had no risk factor. This leads to a programme of universal neonatal screening for early detection.

21. OTOACOUSTIC EMISSIONS (OEA) OAEs are generated at 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 → ossicles → tympanic membrane → ear canal where it is picked up. OAEs are absent if outer hair cells in the cochlea are non functional or there is middle ear effusion or canal debris due to meconium which may persist for 3–4 days. They are normal even when VIIIth nerve is non functional. Thus can be used in the diagnosis of neuropathy of VIIIth nerve.

22. AUDITORY BRAINSTEM RESPONSES (ABR) ABR include the identification of suspected neurological abnormalities of the cranial nerve VIII as well as the associated auditory pathways and estimating hearing sensitivity for those who cannot provide behavioural hearing evaluation information accurately. 

23. The auditory brainstem response (ABR) is an action potential generated by the brainstem in response to the presentation of an auditory stimulus. The auditory brainstem response is made up of a series of seven peaks and troughs which are generated by neural firing at different – but sometimes overlapping – stages of the pathway.

24. The primary measurements from an ABR are the absolute wave latencies, amplitudes, and inter wave intervals between waves I to III, III to V, and I to V. 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 , the infant who passes the test and the hearing is considered normal. Infants who fail these tests are followed up with repeat tests.

25. AROUSAL TEST A high-frequency narrow band noise is presented for 2 s 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.

26. AUDITORY RESPONSE CRADLE Auditory response cradle is a screening device for new borns , where baby is placed in a cradle and his behaviour (trunk and limb movement, head jerk and respiration) in response to auditory stimulation are monitored by transducers. It can screen babies with moderate, severe or profound hearing loss.

27. BEHAVIOUR OBSERVATION AUDIOMETRY Auditory signal presented to an infant produces a change in behaviour, e.g. alerting, cessation of an activity, widening of eyes or facial grimacing 0-6 Month of age Moro’s reflex is one of them and consists of sudden movement of limbs and extension of head in response to sound of 80–90 Db.

28. Cochleopalpebral Reflex, the child responds by a blink to a loud sound. Cessation Reflex, an infant stops activity or starts crying in response to a sound of 90 dB.

29. DISTRACTION TECHNIQUES Used in children 6–18 months old. The child at this age turns his head to locate the source of sound.

30. Test Method The distractor directs the child’s attention to an item covered by their hands. Sound stimulus is presented by the tester, half a second after the item is covered. Distractor observes the child’s response. Sound stimulus (of up to 10 sec) should be presented in the horizontal plane to the ears at an angle, set back 45° between 1 m and 15 cm from the child’s ear. Normal response is a full head turn in the direction of the sound, which is rewarded by the tester.

31. CONDITIONING TECHNIQUES VISUAL REINFORCEMENT AUDIOMETRY (VRA) It is a conditioning technique in which child is trained to look for an auditory stimulus by turning his head. This behaviour is reinforced by a flashing light or an animated toy. This test helps to determine the hearing threshold using standard audiometric techniques. The auditory stimulus is delivered by headphones or better still by insert earphones which are accepted better and are also light weight. Test is well-suited between the developmental age of 6 months to 2 years.

32. Test Method Loudspeakers are placed at 90° from the child and at the child’s head height, at least 1 m away from the child The distractor draws the child’s attention with gentle play. Sound stimulus duration is 2–3 seconds, initially with a concurrent visual reward. Then the stimulus is presented alone and the reinforcer is activated only after the child produces a turning response.

33. PLAY AUDIOMETRY The 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 of the act is reinforced with praise, encouragement or reward. This test can be used in children with developmental age of 2–4 or 5 years.

34. SPEECH AUDIOMETRY The child is asked to repeat the names of certain objects or to point them out on the pictures. The voice can be gradually lowered. In this way, hearing level and speech discrimination can be tested. The test can also be used to examine the child’s expressive ability when he is asked to name the toys like horse, duck or objects like cup, plate, etc.

35. COCHLEAR IMPLANT A cochlear implant is an electronic device that can provide useful hearing and improved communication abilities for persons who have severe to profound sensorineural hearing loss and who cannot benefit from hearing aids. A cochlear implant works by producing meaningful electrical stimulation of the auditory nerve where degeneration of the hair cells in the cochlea has progressed to a point such that amplification provided by hearing aids is no longer effective.

36. COMPONENTS OF A COCHLEAR IMPLANT EXTERNAL COMPONENT It consists of an external speech processor and a transmitter. The speech processor maybe body worn or behind the ear type. INTERNAL COMPONENT It is surgically implanted and comprises the receiver / stimulator package with an electrode array

37. FUNCTIONING OF A COCHLEAR IMPLANT Sound is picked up by the microphone in the speech processor. The speech processor analyses and codes sounds into electrical pulses. The processor uses a variety of coding strategies to deliver meaningful speech parameters from the acoustic stimulus to the nerve.

38. The electrical impulses are sent from the processor to the transmitting coil which in turn sends the signal to the surgically implanted receiver/stimulator via radiofrequency. The receiver/stimulator decodes the signal and transmits it to the electrode array . The electrode array which has been placed in the scala tympani of the cochlea stimulates the spiral ganglion cells . The auditory nerve is thus stimulated and sends these electrical pulses to the brain which are finally interpreted as sound.

39. CANDIDACY PROFILE Cochlear implants may be used both in children and adults. 1. Bilateral severe to profound sensorineural hearing loss 2. Little or no benefit from hearing aids. 3. No medical contraindication for surgery. 4. Realistic expectation. 5. Good family and social support toward habilitation . 6. Adequate cognitive function to be able to use the device.

40. OUTCOMES OF COCHLEAR IMPLANTATION Previous auditory experience (post lingual patients or prior use of hearing aids). 2. Younger age at implantation (especially for prelingual children). 3. Shorter duration of deafness. 4. Neural plasticity within the auditory system.

41. Post lingual children or adults achieve very good benefit. They develop the ability to recognize speech with no or minimal lip reading or visual cues. Prelingually deafened children also develop good speech understanding and language acquisition over a period of time. This can take a couple of years and requires constant auditory-verbal training. Early age at implantation ensures better results and children can be implanted at 12 months of age. Prelingually deafened adults with no or little prior auditory experience obtain very limited benefit from cochlear implantation.

42. EVALUATION OF PATIENT BEFORE IMPLANTATION Detailed history and physical examination Imaging of the temporal bone, cochlea, auditory nerve and brain is carried out using CT and MRI. Audiological evaluation Hearing aid trial and evaluation is mandatory in determining the candidacy for cochlear implantation. This may include aided free-field sound detection thresholds, as well as aided speech perception and discrimination scores.

43. Speech and language evaluation is required to assess the Communicative status and to determine any developmental language or articulation disorders. This will also form a baseline for further evaluations post implantation to help assess progress and identify areas of deficit in speech perception. Psychological evaluation is performed where there may concerns regarding the cognitive status or mental function of the patient.

44. SURGERY The principle of cochlear implant surgery is to place the electrode array within the scala tympani of the cochlea. This allows the electrodes to be in close proximity to the spiral ganglion cells and their dendrites (that lie in the modiolus and osseous spiral lamina of the cochlea, respectively).

45. TWO SURGICAL TECHNIQUES TO APPROACH THE COCHLEA FOR IMPLANTATION: (1) THE FACIAL RECESS APPROACH A simple cortical mastoidectomy is done first and the short process of the incus and the lateral semi-circular canal are identified. The facial recess is opened by performing a posterior tympanotomy. The stapes, promontory and round window niche are identified. Cochleostomy is then performed anteroinferior to the round window membrane to a diameter of 1.0–1.6 mm depending onthe electrode to be used.

46. (2) THE PERICANAL TECHNIQUES A Tympanomeatal flap is elevated to perform a cochleostomy either by Endaural or Postaural approach. In the Pericanal techniques a bony tunnel is drilled along the external canal towards the middle ear. The examples of Pericanal techniques include the Veria and Suprameatal recess approach.

47. The device is placed in the “well” created and is secured with ties. The electrode array is gently and gradually inserted through the cochleostomy till complete insertion has been achieved. Electrophysiological testing is carried out to check that the electrode impedances and telemetry responses are satisfactory.

48. POSTOPERATIVE MAPPING (PROGRAMMING) OF DEVICE AND HABILITATION Activation of the implant is done 3–4 weeks after implantation. Following this the implant is “programmed” or “mapped.” Mapping is done on a regular basis during postoperative rehabilitation to fine-tune the processor and get the best performance as the patient gets used to hearing with the implant. All patients need auditory-verbal therapy. In auditory-verbal therapy, the emphasis is laid on making the child listen and speak like a normal person rather than use lip reading and visual cues. Learning to listen takes time and requires concerted efforts from the patient, the family and the person providing habilitation services.

49. COMPLICATIONS OF COCHLEAR IMPLANTATION

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