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40. Auditory steady-state response in cochlear implant patients: Electrical artifact or physiologic response?
Society Proceedings / Clinical Neurophysiology 119 (2008) e99–e164
39. Auditory steady state responses in screening—G. Savio, M.C. Perez Abalo, J.A. Gaya, O. Hernandez, E. Mijares (Cuba)
e109
be indicative that electrical artefact rather than a physiological response was recorded. doi:10.1016/j.clinph.2008.04.056
Recent developments in techniques and instrumentation as well as strong legislative efforts, have made neonatal hearing screening a reality nowadays in many countries worldwide. Comprehensive screening programs must be organized, ensuring not only early detection, but also diagnosis, treatment and intervention of the hearing impaired child. Over the last decade the auditory steady state evoked responses (ASSR) elicited by single or multiple modulated tones have been demonstrated a useful technique for objective frequency specific audiometry in infancy. The test accuracy and prognostic validity of Multiple Auditory Steady State Responses (MSSR) and click Auditory Brainstem Responses (cabr) was compared within the context of a targeted screening protocol. A sample of 508 high risk babies was first screened using cabr and MSSR (0.5 and 2 kHz). All children (failed/pass) were called back at 3–4 years of age to determine their hearing status (pure tone audiometry). Although both methods showed an equally good test performance in the first screen (sensitivity: 100%, and specificity: 92–95%) the MSSR may have some potential advantage to identify low frequency hearing loss. Furthermore, the confirmatory audiometry with MSSR predicted the child hearing status more accurately than the cabr. The MSSR can provide valuable information for the diagnosis and management of infants earlier detected by a screening protocol and further developed might be also useful as a screening test. doi:10.1016/j.clinph.2008.04.055
40. Auditory steady-state response in cochlear implant patients: Electrical artifact or physiologic response?—A. Torres, M.C. Pe´rez, E. Mijares, E. Eimil (Cuba) The aims of this work were to characterize the electrophysiological response obtained by measuring auditory steady-state responses (ASSR) in patients with a cochlear implant (Clarion, Advanced Bionics). Ten implantees were examined with four different carrier frequencies (500, 1000, 2000 and 4000 Hz) modulated at frequency of 115 Hz. All ASSR recordings were obtained using the AUDIX system (NEURONIC S.A.). Testing was performed in a sound attenuated room. The protocol consisted of measuring amplitude and phase at different intensities. Physiological and behavioral thresholds for each subject were also examined. The mean and standard deviation of the signal amplitude was 0.17 ± 039 with a minimum of 0.003 lv and maximum of 2.8 lv. The difference between physiological and behavioral threshold were of 7, 3, 1 and 6 for frequencies of 0.5, 1, 2 and 4 khz respectively. Using circular statistic we also analyzed the phase behavior, the results do not evidence difference in frequencies or the intensities tested. The analysis of response growth as a function of stimulus intensity showed a non-lineal behavior. Thresholds estimated with ASSR demonstrated poor correlation with the subjective thresholds. The magnitude of the amplitude does not correspond with previous reports in normal or hearing impair patient and the response phase don’t change with the frequency. This might
41. Clinical usefulness of the MSSR to air and bone conducted stimuli in normal hearing and hearing impaired children—M.C. Herna´ndez, M.C. Pe´rez, J.A. Gaya, L. Charro, E. Rodrı´guez, L. Rioja (Cuba) The accuracy of multiple auditory steady state responses (MSSR) to estimate frequency-specific hearing thresholds for both air (AC) and bone conducted (BC) stimuli was evaluated. A second aim of this study was to examine the possibility of artefactual responses elicited by AC and BC stimuli in the AUDIX system. Three groups of children were tested: (G1) normal hearing children N = 15; (G2) children with conductive hearing losses N = 15; (G3) patients with profound hearing losses N = 15. The behavioural audiometric thresholds (BHT) and the frequency specific ASSR thresholds (RTH) elicited by single and multiple AC (and BC) stimuli were determined in all children. In all, a reasonable close correspondence was found between the behavioural and the physiological thresholds to both AC and BC stimuli. Also in both groups the ASSR airbone gap correlated significantly with the corresponding behavioural estimate. Although most children in G3 showed absent responses at high intensities there were very few artefactual responses in the recordings to the AC-stimuli and none for BC stimuli. The MSSR technique can provide reliable estimates of the AC and BC hearing thresholds and the air-bone gap in normal and hearing impaired children. doi:10.1016/j.clinph.2008.04.057
42. Association between spontaneous EEG and doppler velocimetry of cerebral blood flow in newborns during—D.A. Botero Rosas, A.F.C. Infantosi (Colombia) Cerebral blood flow (CBF) alterations in the newborns (NB) can lead to brain damage by decrease in the oxygen and glucose. In order to understand the mechanisms involved, association between the EEG (right front-temporal derivation) and the Doppler velocimetry of the middle cerebral artery from to term NB is investigated. These signals were simultaneously collected from 20 NB and then epochs during quiet sleep were selected. EEG power in the theta band at each second was estimated. For CBF, obtained from the velocimetry, the average velocity (Vm) was extracted for each heart cycle. In order to investigate the association in the time (cross correlation function-CCF) and frequency domains (magnitude square coherence-MSC) signal processing techniques with missing samples were developed. We have found that during TA, CCF between theta and Vm resulted in the maximum value of the median close to 0.24 around 5 s (p < 0.05; anticipated to Vm) for 84.6% of the NB with p < 0.05. The maximum of the MSC median occurred around 0.10 Hz in 92.3% of the NB (p < 0.05). A distinct behavior was observed for HVS. These findings indicate an association between the neuronal activity and CBF during TA. The high coherence
39. Auditory steady state responses in screening—G. Savio, M.C. Perez Abalo, J.A. Gaya, O. Hernandez, E. Mijares (Cuba)
e109
be indicative that electrical artefact rather than a physiological response was recorded. doi:10.1016/j.clinph.2008.04.056
Recent developments in techniques and instrumentation as well as strong legislative efforts, have made neonatal hearing screening a reality nowadays in many countries worldwide. Comprehensive screening programs must be organized, ensuring not only early detection, but also diagnosis, treatment and intervention of the hearing impaired child. Over the last decade the auditory steady state evoked responses (ASSR) elicited by single or multiple modulated tones have been demonstrated a useful technique for objective frequency specific audiometry in infancy. The test accuracy and prognostic validity of Multiple Auditory Steady State Responses (MSSR) and click Auditory Brainstem Responses (cabr) was compared within the context of a targeted screening protocol. A sample of 508 high risk babies was first screened using cabr and MSSR (0.5 and 2 kHz). All children (failed/pass) were called back at 3–4 years of age to determine their hearing status (pure tone audiometry). Although both methods showed an equally good test performance in the first screen (sensitivity: 100%, and specificity: 92–95%) the MSSR may have some potential advantage to identify low frequency hearing loss. Furthermore, the confirmatory audiometry with MSSR predicted the child hearing status more accurately than the cabr. The MSSR can provide valuable information for the diagnosis and management of infants earlier detected by a screening protocol and further developed might be also useful as a screening test. doi:10.1016/j.clinph.2008.04.055
40. Auditory steady-state response in cochlear implant patients: Electrical artifact or physiologic response?—A. Torres, M.C. Pe´rez, E. Mijares, E. Eimil (Cuba) The aims of this work were to characterize the electrophysiological response obtained by measuring auditory steady-state responses (ASSR) in patients with a cochlear implant (Clarion, Advanced Bionics). Ten implantees were examined with four different carrier frequencies (500, 1000, 2000 and 4000 Hz) modulated at frequency of 115 Hz. All ASSR recordings were obtained using the AUDIX system (NEURONIC S.A.). Testing was performed in a sound attenuated room. The protocol consisted of measuring amplitude and phase at different intensities. Physiological and behavioral thresholds for each subject were also examined. The mean and standard deviation of the signal amplitude was 0.17 ± 039 with a minimum of 0.003 lv and maximum of 2.8 lv. The difference between physiological and behavioral threshold were of 7, 3, 1 and 6 for frequencies of 0.5, 1, 2 and 4 khz respectively. Using circular statistic we also analyzed the phase behavior, the results do not evidence difference in frequencies or the intensities tested. The analysis of response growth as a function of stimulus intensity showed a non-lineal behavior. Thresholds estimated with ASSR demonstrated poor correlation with the subjective thresholds. The magnitude of the amplitude does not correspond with previous reports in normal or hearing impair patient and the response phase don’t change with the frequency. This might
41. Clinical usefulness of the MSSR to air and bone conducted stimuli in normal hearing and hearing impaired children—M.C. Herna´ndez, M.C. Pe´rez, J.A. Gaya, L. Charro, E. Rodrı´guez, L. Rioja (Cuba) The accuracy of multiple auditory steady state responses (MSSR) to estimate frequency-specific hearing thresholds for both air (AC) and bone conducted (BC) stimuli was evaluated. A second aim of this study was to examine the possibility of artefactual responses elicited by AC and BC stimuli in the AUDIX system. Three groups of children were tested: (G1) normal hearing children N = 15; (G2) children with conductive hearing losses N = 15; (G3) patients with profound hearing losses N = 15. The behavioural audiometric thresholds (BHT) and the frequency specific ASSR thresholds (RTH) elicited by single and multiple AC (and BC) stimuli were determined in all children. In all, a reasonable close correspondence was found between the behavioural and the physiological thresholds to both AC and BC stimuli. Also in both groups the ASSR airbone gap correlated significantly with the corresponding behavioural estimate. Although most children in G3 showed absent responses at high intensities there were very few artefactual responses in the recordings to the AC-stimuli and none for BC stimuli. The MSSR technique can provide reliable estimates of the AC and BC hearing thresholds and the air-bone gap in normal and hearing impaired children. doi:10.1016/j.clinph.2008.04.057
42. Association between spontaneous EEG and doppler velocimetry of cerebral blood flow in newborns during—D.A. Botero Rosas, A.F.C. Infantosi (Colombia) Cerebral blood flow (CBF) alterations in the newborns (NB) can lead to brain damage by decrease in the oxygen and glucose. In order to understand the mechanisms involved, association between the EEG (right front-temporal derivation) and the Doppler velocimetry of the middle cerebral artery from to term NB is investigated. These signals were simultaneously collected from 20 NB and then epochs during quiet sleep were selected. EEG power in the theta band at each second was estimated. For CBF, obtained from the velocimetry, the average velocity (Vm) was extracted for each heart cycle. In order to investigate the association in the time (cross correlation function-CCF) and frequency domains (magnitude square coherence-MSC) signal processing techniques with missing samples were developed. We have found that during TA, CCF between theta and Vm resulted in the maximum value of the median close to 0.24 around 5 s (p < 0.05; anticipated to Vm) for 84.6% of the NB with p < 0.05. The maximum of the MSC median occurred around 0.10 Hz in 92.3% of the NB (p < 0.05). A distinct behavior was observed for HVS. These findings indicate an association between the neuronal activity and CBF during TA. The high coherence