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Amplitude Changes of the Electrically Evoked Compound Action Potential in Children with Cochlear Implants: Preliminary Results
Alireza Pourjavid,Mansoureh Adel Ghahraman,Mahin Sedaie,Hessam-Al-Din Emamjome
Iranian Journal of Pediatrics , 2011,
Abstract: Objective:Use of electrical instead of acoustical stimulation has made much objective electrophysiological evaluation possible. This is useful for management process of young children before and after the cochlear implant. These evaluations have been used for assessment of neuronal survival before cochlear implant and for monitoring of prosthesis function during and after the surgery. Electrically evoked compound action potential is one of these tests which makes a valid and reliable objective evaluation possible. The aim of this study was to evaluate the potentials amplitude changes three months after receiving the device in pediatric cochlear implant recipients. Methods:In this longitudinal study, changes of the potentials amplitude in four given electrodes in four sessions after receiving the device are evaluated by approximately one month intervals in children implanted in Amir Alam and Hazrat-e-Rasoul hospitals, Tehran in July to December 2007. Findings:The mean amplitude of the electrodes did not significantly change in different sessions, while there was significant difference between the first and the other electrodes responses in every session (P<0.05). Conclusion:Due to high reliability of the responses, the clinician can fit the speech processor for a long time. Better responses in apical electrodes may lead to develop an effective coding strategy.
Assessment of Electrically Evoked Auditory Brain Stem Response of 30 Implanted Patients With Nucleus Multichannel Cochlear Implant
Naser Akbarlou,Dr.Mohammad Farhadi,Dr. Ahmad Daneshi,Dr. Gholamreza Olyaei
Audiology , 2001,
Abstract: Methods and Materials: Investigation of electrically evoked auditory brain stem response (EABR) is a new issue, especially in implanted patients. Experiments were performed in C.I Center of Iranian Institute for Science and research expansion,1996 on 30 implanted patients with 22 spectra and MSP cochlear implant system and 30 normal subjects with the range of 3-33 years. Findings: I- EABR was obtained in the implanted patients. 2- Absolute latency of EABR waves is 1-1.5 ms shorter than ABR waves ‘P<0.05). 3-Absolute latency of wave V decreases as a function of electric stimulus magnitude (P<0.05). 4- No significant difference was observed in IPL Ill-V between ABR and EABR.
Impedance and Electrically Evoked Compound Action Potential (ECAP) Drop within 24 Hours after Cochlear Implantation  [PDF]
Joshua Kuang-Chao Chen, Ann Yi-Chiun Chuang, Georg Mathias Sprinzl, Tao-Hsin Tung, Lieber Po-Hung Li
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071929
Abstract: Previous animal study revealed that post-implantation electrical detection levels significantly declined within days. The impact of cochlear implant (CI) insertion on human auditory pathway in terms of impedance and electrically evoked compound action potential (ECAP) variation within hours after surgery remains unclear, since at this time frequency mapping can only commence weeks after implantation due to factors associated with wound conditions. The study presented our experiences with regards to initial switch-on within 24 hours, and thus the findings about the milieus inside cochlea within the first few hours after cochlear implantation in terms of impedance/ECAP fluctuations. The charts of fifty-four subjects with profound hearing impairment were studied. A minimal invasive approach was used for cochlear implantation, characterized by a small skin incision (≈2.5 cm) and soft techniques for cochleostomy. Impedance/ECAP was measured intro-operatively and within 24 hours post-operatively. Initial mapping within 24 hours post-operatively was performed in all patients without major complications. Impedance/ECAP became significantly lower measured within 24 hours post-operatively as compared with intra-operatively (p<0.001). There were no differences between pre-operative and post-operative threshold for air-conduction hearing. A significant drop of impedance/ECAP in one day after cochlear implantation was revealed for the first time in human beings. Mechanisms could be related to the restoration of neuronal sensitivity to the electrical stimulation, and/or the interaction between the matrix enveloping the electrodes and the electrical stimulation of the initial switch-on. Less wound pain/swelling and soft techniques both contributed to the success of immediate initial mapping, which implied a stable micro-environment inside the cochlea despite electrodes insertion. Our research invites further studies to correlate initial impedance/ECAP changes with long-term hearing/speech performance.
Site of cochlear stimulation and its effect on electrically evoked compound action potentials using the MED-EL standard electrode array
Stefan Brill, Joachim Müller, Rudolf Hagen, Alexander M?ltner, Steffi-Johanna Brockmeier, Thomas Stark, Silke Helbig, Jan Maurer, Thomas Zahnert, Clemens Zierhofer, Peter Nopp, Ilona Anderson, Stefan Strahl
BioMedical Engineering OnLine , 2009, DOI: 10.1186/1475-925x-8-40
Abstract: Recordings of auditory nerve responses were conducted in 67 subjects to demonstrate the feasibility of ECAP recordings using the Auditory Nerve Response Telemetry (ART?) feature of the MED-EL MAESTRO system software. These recordings were then analyzed based on the site of cochlear stimulation defined as basal, middle and apical to determine if the amplitude, threshold and slope of the amplitude growth function and the refractory time differs depending on the region of stimulation.Findings show significant differences in the ECAP recordings depending on the stimulation site. Comparing the apical with the basal region, on average higher amplitudes, lower thresholds and steeper slopes of the amplitude growth function have been observed. The refractory time shows an overall dependence on cochlear region; however post-hoc tests showed no significant effect between individual regions.Obtaining ECAP recordings is also possible in the most apical region of the cochlea. However, differences can be observed depending on the region of the cochlea stimulated. Specifically, significant higher ECAP amplitude, lower thresholds and steeper amplitude growth function slopes have been observed in the apical region. These differences could be explained by the location of the stimulating electrode with respect to the neural tissue in the cochlea, a higher density, or an increased neural survival rate of neural tissue in the apex.The Clinical Investigation has the Competent Authority registration number DE/CA126/AP4/3332/18/05.Objective measures are a widely used and valuable tool in the field of cochlear implants (CIs). During surgery they provide first indications of successful implantation and after surgery they are used to facilitate the individual fitting of stimulation parameters. One objective measure of the auditory nerve's response to stimulation is the Electrically Evoked Compound Action Potential (ECAP). This response is particularly advantageous because it allows the clinici
Auditory neuropathy/auditory dyssynchrony in children with cochlear implants
Carvalho, Ana Claudia Martinho de;Bevilacqua, Maria Cecilia;Sameshima, Koichi;Costa Filho, Orozimbo Alves;
Brazilian Journal of Otorhinolaryngology , 2011, DOI: 10.1590/S1808-86942011000400012
Abstract: the electrical stimulation generated by the cochlear implant (ci) may improve the neural synchrony and hence contribute to the development of auditory skills in patients with auditory neuropathy/auditory dyssynchrony (an/ad). aim: prospective cohort cross-sectional study to evaluate the auditory performance and the characteristics of the electrically evoked compound action potential (ecap) in 18 children with an/ad and cochlear implants. material and methods: the auditory perception was evaluated by sound field thresholds and speech perception tests. to evaluate ecap's characteristics, the threshold and amplitude of neural response were evaluated at 80hz and 35hz. results: no significant statistical difference was found concerning the development of auditory skills. the ecap's characteristics differences at 80 and 35hz stimulation rate were also not statistically significant. conclusions: the ci was seen as an efficient resource to develop auditory skills in 94% of the an/ad patients studied. the auditory perception benefits and the possibility to measure ecap showed that the electrical stimulation could compensate for the neural dyssynchrony caused by the an/ad. however, a unique clinical procedure cannot be proposed at this point. therefore, a careful and complete evaluation of each an/ad patient before recommending a cochlear implant is advised. clinical trials: nct01023932
Cross-modal plasticity in deaf child cochlear implant candidates assessed using visual and somatosensory evoked potentials  [cached]
Lidia E. Charroó-Ruíz,Thais Picó,María C. Pérez-Abalo,María del Carmen Hernández
MEDICC Review , 2013,
Abstract: INTRODUCTION: Cross-modal plasticity has been extensively studied in deaf adults with neuroimaging studies, yielding valuable results. A recent study in our laboratory with deaf-blind children found evidence of cross-modal plasticity, revealed in over-representation of median nerve somatosensory evoked potentials (SEP N20) in left hemisphere parietal, temporal and occipital regions. This finding led to asking whether SEP N20 changes are peculiar to deaf-blindness or are also present in sighted deaf children. OBJECTIVE: Assess cross-modal plasticity in deaf child cochlear implant candidates using neurophysiological techniques (visual evoked potentials and median nerve somatosensory evoked potentials). METHODS: Participants were 14 prelingually deaf children assessed in the Cuban Cochlear Implant Program. Flash visual-evoked potentials and SEP N20 were recorded at 19 scalp recording sites. Topographic maps were obtained and compared to those of control group children with normal hearing. Analysis took into account duration of hearing loss. RESULTS: Topographic maps of flash visual-evoked potentials did not show changes in deaf child cochlear implant candidates. However, SEP N20 from right median nerve stimulation did show changes from expansion of cortical activation into the left temporal region in deaf children aged >7 years, which was interpreted as neurophysiological evidence of cross-modal plasticity, not previously described for this technique and type of somatosensory stimulus. We interpret this finding as due in part to duration of deafness, particularly related to handedness, since expansion was selective for the left hemisphere in the children, who were all right-handed. CONCLUSIONS: Cortical over-representation of SEP N20 in the left temporal region is interpreted as evidence of cross-modal plasticity that occurs if the deaf child does not receive a cochlear implant early in life-before concluding the critical period of neural development- and relies on sign language for communication.
Vestibular Dysfunctions in Cochlear Implant Patients; A Vestibular Evoked Myogenic Potential Study  [PDF]
Masoud Motasaddi Zarandy,Mohammad Taghi Khorsandi,Nima Rezazadeh,Nasrin Yazdani
Audiology , 2011,
Abstract: Background and Aim: Vestibular evoked myogenic potential in response to click or short tone burst stimuli have been used as a clinical test for distinguish saccule and inferior vestibular nerve diseases. Different studies show that cochlear implant could have inverse effects on vestibular structures. We aimed to investigate vestibular evoked myogenic potential in unilateral cochlear implanted individuals in compare to normal individuals.Methods: Thirty-three unilateral cochlear implanted patients (mean age 19.96 years) and 30 normal hearing individuals (mean age 24-27 years) as control group were enrolled in this cross- sectional study. Absolute latencies and amplitudes of myogenic potential responses were measured and compared in both groups.Results: Myogenic potential recorded in both ears of all controls were normal. No response could be recorded in 16 patients (48.48%) from both ears. In three patients, responses were recorded in both ears though the amplitude of waves was reduced in implanted ear. Unilateral response could be recorded in 14 patients only in their non-implanted ear.Conclusion: Vestibular evoked myogenic potential test is a useful tool for assessing saccular function in cochlear implant patients. Damages of osseous spiral lamina and basilar membrane after cochlear implantation could result in dysfunctions of vestibular organs specially saccule. It seems that saccule could be easily damaged after cochlear implantation. This would cause absence or reduced amplitudes in myogenic potential.
In-vitro characterization of a cochlear implant system for recording of evoked compound action potentials
Christian Neustetter, Matthias Zangerl, Philipp Spitzer, Clemens Zierhofer
BioMedical Engineering OnLine , 2012, DOI: 10.1186/1475-925x-11-22
Abstract: In-vitro setup: The cochlear implant, including all attached electrodes, was fixed in a tank of physiologic saline solution. Sinusoidal signals of the same frequency but with different amplitudes were delivered via a signal generator for measuring and recording on a single electrode.Computer simulations: A basic mathematical model including the main elements of the recording system, i.e. amplification and digitalization stage, was developed. For this, digital output for sinusoidal input signals of different amplitudes were calculated using in-vitro recordings as reference.Using an averaging of 100 measurements the recording system behaved linearly down to approximately -60 dB of the input signal range. Using the same method, a system resolution of 10 μV was determined for sinusoidal signals. The simulation results were in very good agreement with the results obtained from in-vitro experiments.The recording system implemented in the MED-EL PULSARCI100 cochlear implant for measuring the evoked compound action potential of the auditory nerve operates reliably. The developed mathematical model provides a good approximation of the recording system.Cochlear implants (CIs) are prostheses that aim to facilitate auditory perception and speech understanding in patients suffering from profound hearing loss. In normal hearing persons, hair cells inside the cochlea transform acoustic signals into complex patterns of neural signals. These are then transported along the auditory nerve to the brain where they are perceived as sound. In a typical CI patient the hair cells are damaged or absent. CIs make up for this loss by delivering electrical pulses to electrodes located inside the cochlea, which in turn stimulate auditory nerve cells to elicit hearing sensations [1,2]. Many studies have demonstrated that cochlear implantation improves the daily life of patients [3-5], and in particular allows young children with congenital deafness to experience almost normal hearing and speech d
Development of Brainstem-Evoked Responses in Congenital Auditory Deprivation  [PDF]
J. Tillein,S. Heid,E. Lang,R. Hartmann,A. Kral
Neural Plasticity , 2012, DOI: 10.1155/2012/182767
Abstract: To compare the development of the auditory system in hearing and completely acoustically deprived animals, naive congenitally deaf white cats (CDCs) and hearing controls (HCs) were investigated at different developmental stages from birth till adulthood. The CDCs had no hearing experience before the acute experiment. In both groups of animals, responses to cochlear implant stimulation were acutely assessed. Electrically evoked auditory brainstem responses (E-ABRs) were recorded with monopolar stimulation at different current levels. CDCs demonstrated extensive development of E-ABRs, from first signs of responses at postnatal (p.n.) day 3 through appearance of all waves of brainstem response at day 8?p.n. to mature responses around day 90?p.n.. Wave I of E-ABRs could not be distinguished from the artifact in majority of CDCs, whereas in HCs, it was clearly separated from the stimulus artifact. Waves II, III, and IV demonstrated higher thresholds in CDCs, whereas this difference was not found for wave V. Amplitudes of wave III were significantly higher in HCs, whereas wave V amplitudes were significantly higher in CDCs. No differences in latencies were observed between the animal groups. These data demonstrate significant postnatal subcortical development in absence of hearing, and also divergent effects of deafness on early waves II–IV and wave V of the E-ABR. 1. Introduction The auditory system demonstrates extensive developmental changes during postnatal life, both in humans as well as in altricial animals (review in [1]). Which developmental effects are caused by experience and which are preprogrammed by genetic makeup (independent of hearing experience; comp. [2, 3]) is not always straightforward. An interesting model in resolving this question is the congenitally deaf cat (CDCs, [4]). CDCs show a cochlear degeneration before hearing onset that prevents hearing experience. However, the spiral ganglion cells are well preserved [5]. This is a substantial advantage in comparison to pharmacological deafening, where the numbers of surviving spiral ganglion cells decrease within short time down to less than 50%, in some down to 10% of the counts in hearing counterparts [6]. Loss of spiral ganglion cells may lead to a down-regulation in supply of trophic factors to the cochlear nucleus (denervation effects). Loss of spiral ganglion cells is also a confounding factor for developmental studies, further aggravated by the interindividual variability in the ganglion cell loss. Electrical stimulation of the auditory nerve may thus yield a different extent of
Cochlear Implantation after Bacterial Meningitis in Infants Younger Than 9 Months  [PDF]
B. Y. Roukema,M. C. Van Loon,C. Smits,C. F. Smit,S. T. Goverts,P. Merkus,E. F. Hensen
International Journal of Otolaryngology , 2011, DOI: 10.1155/2011/845879
Abstract: Objective. To describe the audiological, anesthesiological, and surgical key points of cochlear implantation after bacterial meningitis in very young infants. Material and Methods. Between 2005 and 2010, 4 patients received 7 cochlear implants before the age of 9 months (range 4–8 months) because of profound hearing loss after pneumococcal meningitis. Results. Full electrode insertions were achieved in all operated ears. The audiological and linguistic outcome varied considerably, with categories of auditory performance (CAP) scores between 3 and 6, and speech intelligibility rating (SIR) scores between 0 and 5. The audiological, anesthesiological, and surgical issues that apply in this patient group are discussed. Conclusion. Cochlear implantation in very young postmeningitic infants is challenging due to their young age, sequelae of meningitis, and the risk of cochlear obliteration. A swift diagnostic workup is essential, specific audiological, anesthesiological, and surgical considerations apply, and the outcome is variable even in successful implantations. 1. Introduction Current standards for cochlear implantation in infants with severe congenital sensorineural hearing loss (SNHL) advocate an age at implantation between 9 and 12 months. On the one hand, a growing body of evidence indicates that hearing rehabilitation is more effective when the patient is implanted at a young age [1–4]. On the other hand, a certain period of time is needed to determine a reliable hearing threshold, to allow for improvement of hearing due to maturation of the auditory system after birth, and to test the performance of the patient with hearing aids [5]. Furthermore, the benefits of cochlear implantation before the age of 9 months should be weighed against the higher risk of anesthesia at this young age [5]. In case of sensorineural hearing loss caused by acute bacterial meningitis, different considerations apply. A swift diagnostic workup is imperative because of the risk of cochlear fibrosis and subsequent obliteration of the cochlear lumen, which may occur within weeks after the onset of meningitis, especially if the meningitis is caused by pneumococci [6, 7]. This diagnostic workup should include a thorough evaluation of the hearing as well as adequate imaging of the cochlea in order to assess the need and feasibility of cochlear implantation. In infants that suffer from postmeningitic SNHL, this may lead to an indication for cochlear implantation at an age younger than 9 months. If so, this patient group presents the cochlear implant (CI) team with a very specific
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