THE IMPORTANCE OF THE BENEFITS OF THE COCHLEAR IMPLANT IN SINGLE SIDED DEAFNESS IN CHILDREN – EVENTS RELATED POTENTIALS (ERP-P300) Tânia Martins1, Diogo Ribeiro1, Jorge Oliveira2, Mafalda Almeida1, Vera Lourenço1, João Paço1,3 1 – Hospital CUF Infante Santo, Lisbon, Portugal 2 – Copelab, Universidade Lusófona de Humanidades e Tecnologias, Lisbom, Portugal 3 – NOVA Medical School, Universidade Nova de Lisboa, Lisbon, Portugal
Introduction
Results
Cochlear implantation has become a standard therapy for children with bilateral profound hearing loss, resulting in substantial and sustainable benefits for the development of expressive and receptive language skills and cognition. 1 On the other hand, cochlear implantation in the treatment of congenital Single Sided Deafness (SSD) in children shows great reluctance, despite the know impact on socialemotional development in children. 1,2 Recently, several studies have shown that a cochlear implant (CI) is a suitable and effective treatment for hearing rehabilitation of adults with SSD, with benefits such as speech comprehension in noise and sound localization. 3,4 In children with congenital SSD it seems that cochlear implantation may provide some of the benefits of binaural hearing if implantation occurs within the critical period of bilateral auditory development and so enable binaural development of auditory pathways and prevent permanent reorganization of the auditory functions, however the benefits of cochlear implantation in these cases still need to be investigated further. 2,5
------ With CI (rare) ------ Without CI (rare) ------ With CI (frequent) ------ Whithout CI (frequent)
Figure 1: JS patient with and without CI with white noise.
Figure 2: MG patient with and without CI with white noise
In recent years, the P300 has been emphasized in the investigation of the benefits of using the CI. This method reflects individual’s cognitive ability to detect and respond to a stimulus, verifying a correlation between a greater amplitude with a better discrimination performance, both at the syllabic and word level word. 6
Methodology The main objective of this study was to evaluate the benefit of the CI on the cognitive ability to differentiate verbal stimuli from background noise through an Event-related Potential (P300). Following this, a specific objective is established: to explore the effects of different time lengths of hearing deprivation. The sample contained 2 participants presenting with SSD and utilizing a CI (Cochlear Nucleus 6, of 22 electrodes). The electrodes were placed on the scalp according to the international system 10-20 for electrode placement coordinates. 7 The stimuli were presented in the Oddball Paradigm, in which a rare stimulus (oddball) is presented randomly with a probability of 20% and alternated with the frequent stimulus, the rare stimulus cannot occur consecutively. The rare stimuli were at an intensity of 65 dB nHL and the background noise at 50 dB nHL, SNR of 15 dB. The consonant/vowel (CV), /ba /ga, was used as the verbal stimulus, with the phoneme /ba/ the frequent stimulus and /ga/ the rare one, in a total of 200 presentations, in which 160 were the frequent stimulus and 40 were the rare stimulus.
Results The results from the P300 for the JS patient in the WN (fig. 1) shows higher amplitudes in the P300 wave in the W/ CI condition compared to the amplitudes in the W/O CI condition in all the electrodes. In the MG patient in the WN (fig. 2) larger amplitudes in the W/ CI condition are also observed in all the electrodes except for Cz and Fz. During the analysis of the topographic maps, it is observed that a greater activation corresponds to a greater amplitude, in the W/ CI conditions, in both the JS and MG patients (fig.3), compared to the W/O CI condition. There is also a lower activation of the cortical area in MG compared to JS, MG activation being more in the posterior zone than JS. Regarding the latencies JS in the WN presents a higher latency in the W/ CI condition (600 ms) compared to the W/O CI condition (598 ms); also MG in WN W/ CI (896 ms) and W/O CI (596 ms).
Bibliography
Figure 3: Topographic maps of patients with and without CI with White noise
Conclusion
SSD leads to extensive adaptation of the central auditory system and consequently reflects its representation in the brain. In this study, we could verify this effect after a long period of hearing deprivation, however this adaptation can be reversed through auditory rehabilitation with the CI, or even prevented by early implantation in the case of children, whose benefit at cortical level were verified through the results of the P300. There was a clear benefit of the CI in discriminating verbal stimuli in the presence of background noise in P300, although the overall hearing level in a subject with SSD is similar to that of a person with normal hearing, the main differences and benefits occur at a higher level and considering that the disadvantages of hearing deprivation over a longer time are remarkable, the earlier the implantation, the less severe the effects of the deprivation will be. Although no statistical analysis was performed to confirm the results with certainty, it will be necessary to continue collecting data in order to perform a statistical interference. However, the results found are in agreement with literature.
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Adress for correspondence: Tânia Martins Centro de ORL Hospital CUF Infante Santo Av. Infante Santo, nº34 1350-070 Lisboa Mail:
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