Emissions are low-intensity sounds that may be detected in the external ear canal by a microphone

Transcription

1 OAEs

2 Emissions are low-intensity sounds that may be detected in the external ear canal by a microphone OAE is a pre-neural phenomenon They can be measured even when the 8 th cranial nerve is severely damaged

3 If the ME system is compromised, the acoustic energy detected in the ear canal will be compromised too The actions of ME muscles noted to influence the OAEs characteristics It s vulnerable to acoustic trauma, hypoxia and ototoxic agents, as all of these cause hearing loss and damage to OHCs Emission are of two classes ( Spontaneous or evoked)

4 Kemp has described in 1979 that many normal cochleae are capable of producing sounds without any external stimuli and this known as ( Spontaneous otoacoustic emissions (SOAEs) SAOEs present in about half of normal hearing people and it s recorded as a continuous tonal signal in the external ear canal

5 It s frequency range Hz. However, it might be present below or above these frequencies Its amplitude varied, but generally between -10 to +10 db SPL It s inaudible to the person in whom it s measured

6 Emissions that are elicited following acoustic stimulation EOAE is of different types ( transient and distortion product) and they are useful in; Deferential diagnosis of SNHL Hearing screening of infants and difficult to test patients

7 Monitoring of patients who are susceptible to OHCs damage due to noise exposure or using oto-toxic medications

8 1) They are low intensity sounds ( approximately -20 to db SPL ) Amplitude of EOAEs is related to stimulus amplitude in complex way 2) The temporal and spectral characteristics of the emission will reflect region of cochlea stimulated (produces the emission ); in health ear EOAE will mirror the stimulus

9 3) Emissions can be suppressed or decreased in amplitude by presenting ipsilateral or contralateral stiumli 4) Emissions properties altered in the presence of hearing loss. The probability of recording emissions in the frequencies with hearing loss that exceeds 30 db HL varies inversely with the amount of hearing loss. 5) Emissions are extracted from background noise in the external ear canal by sampling the sound in the ear canal

10 TEOAEs are produced by brief acoustic stimuli like clicks or tone pips Signal-averaging equipment should be used to separate the emissions from the ongoing noise in the ear

11 From 260 to 500 stimuli are presented and the waveform of the responses averaged, together with the ongoing noise in the ear, in order to improve signal to noise ratio SNR TEOAEs are usually elicited from all individuals with normal outer, middle and inner ears When the hearing loss of cochlear origin increases, the amplitude of the response decreases until about 40 db HL hearing where the response will disappear

12 When click stimulus is used, a broad band of frequencies will be present in the TEOAE as a wide area of the cochlea stimulated As a result, when a broad band TEOAE observed, this indicate that the peripheral auditory pathway and the cochlea are un-impaired

13 However, disorders in areas beyond the cochlea like the auditory nerve won t be known Therefore, normal TEOAE does not indicate normal hearing Abnormal ( absent) TEOAE, suggest that the hearing loss is present but it does not reveal what type of hearing loss is present ( conductive or cochlear) It usually evaluated in terms of level, percentage of reproducibility and SNR

14 When two tones of different frequencies and amplitudes (F1, F2 and L1, L2, where F2 > F1), The frequencies are vary by several hundred hertz, are presented to the ear, the normal cochlea responds by producing energy at additional frequencies. (these called DPEOAEs) The DPEOAE at 2F1-F2 is of highest amplitude

15 The conductive pathway should be normal to obtain DPEOAEs, like Transient one It might be present with cochlear loss up to 35 to 40 db HL

16 OAEs are measured by placing a probe in the external ear canal The probe contains: Miniature loudspeaker to produce the evoking stimulus A tiny microphone to pick up the emission and convert it to from sound to electrical signal

17 The probe used to measure the TEOAEs is different from the one for DPEOAEs The probe for DPOAE should have two ports to present two primary tones Because the DPEOAEs are separate in the frequency from the evoking stimuli, averaging background noise of a less problem for its measurement than TEOAEs Fewer stimulus presentations are required for DPEOAES which might reduce the test time slightly

18 Acoustic control of test environment is less critical in OAE testing because the averaged noise is the noise that is present in the subject ear If the subject noise is too high, like crying babies, the emissions might be masked as the microphone is too sensitive and cannot differentiate between different acoustic signals

19 1. High probability that it is a true response and not artifact Analysis window for data collection 2.5 to 4 ms after stimulus delivery ( there is a stimulus artifact at the start of recording therefore, the first few ms of the trace are usually eliminated from the final waveform ) The collection time between ms

20 2. High probability that the response like signal is present at the expected frequency. SNR of 6 db or more at two or more frequencies (1.5 to 4 KHz) 3. Amplitude of response long enough to be within the normal physiological range, 0 db SPL is the minimum

21 Presence of OAEs indicates intact cochlea Conductive pathway should be healthy and intact because strength of the signal traveling from the inner to the outer ear might be attenuated by ME abnormality and in the same time the stimulating signal from outer to the inner ear might be attenuated any conductive abnormality

22 Presence of EOAE suggest that there little or no conductive hearing loss caused by ME problems Presence of EAOE in sensory-neural hearing loss indicates that the outer hair cells are intact and the locus of disorder is retro-cochlear so absent (abnormal) EOAE in the presence of SNHL is confirm cochlear pathology but does not role out retrocochlear involvement

23

24

25

26

27

28 It is a term used to describe disorders that are operationally defined based on a group of clinical findings. The clinical findings varied as a function of child s age.

29 In older children AN is defined by Absent ABR. Poor speech perception. Varying level of hearing loss. Absent acoustic reflexes. Preserved some cochlear functions as evidenced by present OAEs and/ or Cochlear Microphonics.

30 In infants, it s defined by Absent ABR. Present OAEs and /or CM.

31 It s usually of unknown causes. However, some due to Demyelinating disorders It also may seen in some cases of syndromic peripheral pathologies Like ( Charcot-Marie-Tooth syndrome) It s might be inherited as a recessive disorder

32 Its age of onset is usually before 10 years-old. Hearing sensitivity loss ranges from normal to profound and it is often fluctuates and it s progressive in some children. The audiogram configuration varied flat, high frequency, low frequency

33 Speech perception is clearly poorer from the audiogram findings. Acoustic reflexes are absent or elevated AN could be of sensory origin or neural origin.

34 It s a transduction problem with failure of the cochlea to transmit signals to auditory nerve. Most likely origin is the inner hair cells (IHCs), as the presence of OAEs and CM represent normal OHCs functions. Absence of ABR reflects the associated loss of hearing sensitivity.

35 AN (S) like any other sensitivity loss in term of its effect on speech and language acquisition and its amenability to HAs and CI.

36 It is first described as a specific disorder of the auditory nerve that results in a loss of synchrony of the neural firing. It s also referred as auditory dyssynchrony. It may not benefit from conventional amplification (HAs) and Implant treatment as AN(S).

37 Several evaluations and recommendations should be obtained to supplement audiologic findings; includes medical consultations by Otolaryngologists Genetics Neurologists

38 Neonatal follow up Ophthalmologists Additionally, beside consistent audiologic follow up, speech language pathology, early intervention ( specialized with deaf and hearing impaired) and family mental health support should be indicated

39 As the hearing loss is fluctuating and the audiologic test results are conflicting, audiologic monitoring is required 1. Auditory Brainstem Responses (ABR) Cochlear microphonic is important in ruling out sensory loss when click ABR responses are absent at high stimulus level

40 CM waveform originates from the cochlea and not auditory nerve and it appears before wave I It inverts when the stimulus polarity reverses from rarefaction to condensation It is present in children with normal hearing It s abnormally large and may present in absence of other ABR peaks in patients with AN/AD

41 If Auditory neuropathy diagnosed before six months of age, repeating ABR between 3 to 6 months is recommended Gestational age of ME status should be considered when repeating the ABR Preterm infants and those with peri-natal insult should be watched carefully as abnormal ABR might give indication of overall issue of nervous system

42 If ABR continues to be absent after repeating in late gestational age, test does not need to be repeated unless behavioral results improved or the patient is not able to respond behaviorally due to developmental delay Patients who continue to show ABR improvements, several ABRs should be done every 6 to 12 months

43 Tympanometery should be performed using 1000 Hz probe tone for patients below 6 months Acoustic reflexes should be done using 660 Hz probe tone for infants less than 4 months

44 Immittance testing should be attempted at every audiology visit. While, Acoustic reflexes should be tested at least once when the ME status is normal 3. Otoacoustic Emissions EOAEs include both Transient and distortion product are present in auditory neuropathy patients

45 EOAEs could be absent due to middle ear effusion, negative pressure, cerumen, debris in the ear canal or inappropriate probe fit or calibration EOAEs should be done in conjunction with ABR and should be repeated in other visits in conjunction with behavioral and immittance testing

46 Visual Reinforcement Audiometery (VRA) can be attempted at about 5 months to obtain threshold in the sound field testing and with insert earphones VRA should be obtained in frequent sessions to have ear specific and frequency specific information

47 Monitoring every 2-4 months may be indicated based on the test reliability, ME status and developmental status

48 Young children with consistent VRA results are candidates for amplification and Frequency Modulation (FM) system and can be evaluated for cochlear implant candidacy Hearing aids could be fitted using threshold information obtained by VRA Outcome measures should be obtained before and after hearing aid trail

49 Close communication should be enhanced between parents, audiologists, early intervention providers and SLPs to monitor child s progress with the technology and changes in child s auditory behaviors The trail should be long enough so the child is able to accept the hearing aids for most his working hours Cochlear implants should be considered when the child is not making adequate gain even with proper amplification

50 Pediatric otolaryngologist consultation is recommended when permanent hearing loss is identified Otolaryngologists will search the cause of hearing loss Evaluates ME status Look for any syndromic features

51 A SLP, who has an experience working with hard of hearing or deaf children, is valuable source A SLPs are able to set appropriate speech, language and auditory goals and facilitate the development of these goals Information from SLPs can be used to monitor child progress with amplification and to determine the need for cochlear implant

52 Oversee a medical workup (laboratory testing and imaging) From imaging, MRI is sensitive to rollout a space occupying lesion and absence or underdevelopment of 8 th cranial nerve A medical workup is essential for ruling out other causes for audiologic test results that lead to suspicion of auditory neuropathy

53 Visual impairment should be roll out when the hearing loss is identified as it has significant effect in child development and communication Visual communication approach for child with suspected auditory neuropathy is an option

54 Visual communication approach can be used alone or in conjunction with spoken language Good visual ability need to be confirmed for this approach For those with confirmed severe visual impairment or their potential for visual impairment is confirmed, communication modes that are heavily relaying on visual input are not recommended

55 Whenever auditory neuropathy is suspected, a genetics evaluation is warranted, because AN/AD is a significant hearing loss that is related to other health problems Neurology pediatric neurologists should try to rollout these conditions;

56 Friedrich s ataxia, Charcot-Marie-Tooth disease or hereditary sensory motor neuropathy that happened in adults or older children as the classic cases of AN may be actually one of those conditions These conditions are not evident in infants and the diagnosis of AN may be presumptive younger patients with AN usually showing coexisting medical conditions like prematurity, jaundice or cerebral palsy

57 Purposes of neonatal follow up program 1. To facilitate care of premature and high risk infants following neonatal intensive care discharge

58 2. Track the development of high risk infants, to publish research and serves as a resource for the medical community about the needs, interventions and outcomes of high risk infants Infants evaluated at 3, 6,12 and 24 months and annually until 5 years-old

59 Evaluation sessions involve Medical and behavioral history Physical evaluation Neuromuscular evaluation Nutritional assessment Psychological assessment Social needs assessment Physical therapy evaluation

60 A child younger than 3 years should be served by a professional who has knowledge of children and infants with hearing loss These professionals provides; Counseling, therapy and monitoring of the infant or young child s progress Supply information about the effects of hearing loss on child development

61 Family wellness program addresses the stressor caused by the ongoing illnesses combined with hearing loss Family wellness provides individual counseling and parent seminars in a safe and confidential environment

62 A mental health counselor is available as needed to provide encouragement, information, or assess in finding additional counseling services The overall goal of a family wellness program is to strengthen the parents confident in their ability to make important decisions, and to assist the family in finding and learning new information independently