But, what about ASSR in AN?? Is it a reliable tool to estimate the auditory thresholds in those category of patients??

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2 Auditory Steady State Response (ASSR) thresholds have been shown to be highly correlated to bh behavioral thresholds h in adults and older children with normal hearing or those with sensorineural hearing loss (SNHL). Attias et al, (2008) and Jafari et al, (2009). But, what about ASSR in AN?? Is it a reliable tool to estimate the auditory thresholds in those category of patients?? This study was designed to investigate the correlation between the ASSR thresholds and the behavioral ones in auditory neuropathy. Aiming to assess a frequency specific electrophysiological measure to estimate the auditory thresholds particularly the infants and young children with absent or distorted ABR. 2

3 This study was conducted on 15 adult AN patients with different degrees of hearing loss. Ranging in age from 14 to 50 years. Inclusion criteria: i Hearing loss of any degree and configuration shown by PTA with speech discrimination with poorer score comparing to the amount of hearing loss. Absent ABR for 90dBnHL clicks despite of satisfactory thresholds at high frequencies. Intact (TEOAEs). 3

4 The subjects were divided into 3 groups according to the degree of hearing loss; I. Eight ears had mild degree of SNHL II. Fourteen ears had moderate SNHL III. Eight ears had severe SNHL. Frequencies (0.5, 1, 2 and 4 KHz) were evaluated. 4

5 All subjects in the study were subjected to the following procedures : Detailed history taking : including (the prenatal, perinatal and postnatal problems, e.g. hyperbillrubinemia and other sensori-motor neuropathies) Full Otologic examination: To exclude otitis externa, otitis media or other ear pathology. Basic audiological evaluation including: 1-Pure tone audiometry 2-Speech audiometry 3-Acoustic immitance measures Transient Evoked Oto-Acoustic Emission (TEOAEs) : Should be intact. 5

6 Electrophysiological tests: 1- Auditory brainstem response (Click-ABR) 2- Auditory Steady State Response (ASSR): Single channel monaural ASSR was carried out using the GSI AUDERA evoked potential system. (ASSR) is a frequency specific electrophysiological response to rapid auditory stimuli. It relies on statistical measures to determine if and when a threshold is present. ASSR is typically evoked using continuous sinusoids or carrier frequencies (CF) that are either amplitude modulated (AM), frequency modulated (FM) or amplitude and frequency modulated (AM/FM). Latencies of about 10 msec are considered to be most effective and consistently recorded when using SSEPs to assess the hearing of sleeping infants and young children and to achieve this, modulation frequencies greater than 70 Hz may be the most suitable, Sahllop et al, (1983) 6

7 The test stimuli were 0.5, 1, 2, and 4 KHz amplitude and frequency modulated tones individually presented. The test signals were modulated at rates of 74, 81, 88 and 95 Hz respectively. 100% Amplitude modulation and 10% frequency modulation were combined to maximize response amplitude as stated by Rickards et al. (1994). An illustration of 100% Amplitude Modulation of 500,1000, 2000 and 4000 Hz carrier frequencies with different rates of modulation 7

8 It can be elicited by a single carrier tone or several tonal stimuli presented simultaneously at different modulation rates and the three result options are : phase locked indicating that an ASSR has been identified. 8

9 random where no response could be detected under good recording conditions. noise where the detection algorithm detects EEG noise that exceed a predetermined level. 9

10 Threshold was defined as the lowest level at which a statistically significant response could be obtained (phase locked) and for which the next-lowest presentation level showed no response 10

11 There was no significant correlation between the PTT and ASSR results at the majority of the frequencies usually tested in patients with AN/AD. The estimated auditory thresholds measured by ASSR at all frequencies were substantially higher than the PTT measures. The PTA and the ASSR of subject number 2 in group with mild SNHL 11

12 The PTA and the ASSR of subject number 15 in group with severe SNHL 12

13 Comparison between pure tone thresholds in db HL and Auditory Steady State Response thresholds in db HL at 500 Hz across the different studied groups 120 PTA ASSR Hz Mean Mild Moderate to moderate severe Severe 13

14 Comparison between PTAT in db HL and ASSR thresholds in db HL at 1000 Hz across the different studied groups 100 PTA ASSR 1000 Hz Mean Mild Moderate to moderate severe Severe Comparison between PTAT in db HL and ASSR thresholds in db HL at 2000 Hz across the different studied groups 120 PTA ASSR 2000 Hz Mean Mild Moderate to moderate severe Severe 14

15 Comparison between PTAT in db HL and ASSR thresholds in db HL at 4000 Hz across the different studied groups 120 PTA ASSR Hz Mean Mild Moderate to moderate severe Severe No significant correlation between the PTA and the ASSR measures in the different studied groups. 120 ASSR PTA 500 ASSR 500 (r=0.492,p=0.400) 20 PTA 1000,ASSR 1000 (r=0.127,p=0.811) PTA 2000,ASSR 2000 (r=0.409,p=0.421) PTA 4000,ASSR 4000 (r=-0.500,p=0.667) PTA ASSR PTA 500 ASSR 500 (r=0.109,p=0.750) 20 PTA 1000,ASSR 1000 (r=0.118,p=0.762) PTA 2000,ASSR 2000 (r=0.200,p=0.607) PTA 4000,ASSR 4000 (r=0.440,p=0.383) PTA 15

16 No significant correlation between the PTA and the ASSR in the total studied sample ASSR PTA 500 ASSR 500 (r=0.392,p=0.058) PTA 1000,ASSR 1000 (r=-0.018,p=0.946) PTA 2000,ASSR 2000 (r=0.204,p=0.432) PTA 4000,ASSR 4000 (r=0.316,p=0.344) PTA 16

17 1. There was no significant correlation between the PTT and ASSR results. The estimated auditory thresholds measured by ASSR at all frequencies were substantially higher than the PTT measures. 2. The findings of the current study concluded that using ASSR to estimate the auditory thresholds for AN patients particularly the infants seems unreliable. 17

18 However, we can t judge on this result as a final one!! We only tested 80 Hz ASSR ( brain stem origin ) but we have no idea about the reliability of using 40 Hz ASSR ( cortical origin ) in those category of patients. Still, sedations in the 40 Hz ASSR remains the big problem preventing us from testing it in infants and young children. 18