Os potenciais evocados auditivos de tronco encefálico (PEATE) são um instrumento clínico muito útil na avaliação da maturação das vias auditivas em crianças nascidas pré-termo. Objetivos: Observar a maturação da via auditiva pela análise PEATE em crianças nascidas prétermo em três idades (4, 12 e 20 meses de idade). Casuística e Método: Coorte, individual, observacional, comparativo e contemporâneo. O fator em estudo foi crianças nascidas pré-termo e o desfecho à observação da maturação da via auditiva neste grupo, pela análise PEATE, em três avaliações (aos 4, 12 e 20 meses de idade), precedido de avaliação otorrinolaringológica e audiológica com objetivo de garantir que não apresentavam alteração auditiva. Resultados: Ingressaram 73 crianças pré-termo. Não foi encontrada diferença estatística (P>0,05) na comparação dos resultados entre os gêneros, bem como interaural. Houve diferença estatiticamente significante entre idade gestacional, as latências absolutas e intervalos interpicos nas três avaliações realizadas, ocorrendo uma diminuição das latências com o aumento da idade. Verificamos que a maturação da onda I foi mais rápida, e a maturação da onda V foi mais lenta. Podemos perceber que a maturação da via auditiva até o tronco encefálico segue o sentido caudorostral, sendo a da via periférica mais precoce, e a da rostral, mais tardia. Conclusão: Com base nos achados deste estudo, recomendamos que a aplicação do procedimento de avaliação audiológica através do PEATE em crianças nascidas pré-termo, pelo menos até os 20 meses de idade, seja realizado levando-se em conta a idade gestacional a fim de se obter análises fidedignas. / Brainstem Auditory Evoked Potential (BAEP) is a very useful clinical instrument in the evaluation of the auditory pathways maturation in preterm children. Objective: To observe the maturation of the auditory pathway with the use of the BAEP analysis in preterm children at three different ages (four, 12 and 20 months). Casuistry and Method: Group, individual, observational, comparative and contemporary. Preterm children and the outcome to observation of the auditory pathway maturation by the BAEP analysis in three evaluations (at 4, 12 and 20 months of age) were studied. The procedures were preceded by otolaryngological and auditory evaluation with the objective to guarantee the non presence of auditory alteration. Results: Seventy-three preterm children participated in the study. Statistically significant difference was not found (P> 0,05) in the comparison between genders and between ears. There was a statistically significant difference among gestational ages, absolute latencies and interpic intervals in the three evaluations conducted, occurring a reduction of latencies with age increase. We verified that maturation of wave I was faster and the maturation of wave V was slower. We could perceive that the maturation of the auditory pathway up to the brainstem follows the caudorostral direction, being the peripheral pathway more precocious and the rostral pathway more delayed. Conclusion: Based on the findings of this study, we recommend the application of the audiological evaluation procedure using BAEP in preterm children, at least until 20 months of age, by taking into account the gestational age in order to obtain reliable analyses.

Os potenciais evocados auditivos de tronco encefálico (PEATE) são um instrumento clínico muito útil na avaliação da maturação das vias auditivas em crianças nascidas pré-termo. Objetivos: Observar a maturação da via auditiva pela análise PEATE em crianças nascidas prétermo em três idades (4, 12 e 20 meses de idade). Casuística e Método: Coorte, individual, observacional, comparativo e contemporâneo. O fator em estudo foi crianças nascidas pré-termo e o desfecho à observação da maturação da via auditiva neste grupo, pela análise PEATE, em três avaliações (aos 4, 12 e 20 meses de idade), precedido de avaliação otorrinolaringológica e audiológica com objetivo de garantir que não apresentavam alteração auditiva. Resultados: Ingressaram 73 crianças pré-termo. Não foi encontrada diferença estatística (P>0,05) na comparação dos resultados entre os gêneros, bem como interaural. Houve diferença estatiticamente significante entre idade gestacional, as latências absolutas e intervalos interpicos nas três avaliações realizadas, ocorrendo uma diminuição das latências com o aumento da idade. Verificamos que a maturação da onda I foi mais rápida, e a maturação da onda V foi mais lenta. Podemos perceber que a maturação da via auditiva até o tronco encefálico segue o sentido caudorostral, sendo a da via periférica mais precoce, e a da rostral, mais tardia. Conclusão: Com base nos achados deste estudo, recomendamos que a aplicação do procedimento de avaliação audiológica através do PEATE em crianças nascidas pré-termo, pelo menos até os 20 meses de idade, seja realizado levando-se em conta a idade gestacional a fim de se obter análises fidedignas. / Brainstem Auditory Evoked Potential (BAEP) is a very useful clinical instrument in the evaluation of the auditory pathways maturation in preterm children. Objective: To observe the maturation of the auditory pathway with the use of the BAEP analysis in preterm children at three different ages (four, 12 and 20 months). Casuistry and Method: Group, individual, observational, comparative and contemporary. Preterm children and the outcome to observation of the auditory pathway maturation by the BAEP analysis in three evaluations (at 4, 12 and 20 months of age) were studied. The procedures were preceded by otolaryngological and auditory evaluation with the objective to guarantee the non presence of auditory alteration. Results: Seventy-three preterm children participated in the study. Statistically significant difference was not found (P> 0,05) in the comparison between genders and between ears. There was a statistically significant difference among gestational ages, absolute latencies and interpic intervals in the three evaluations conducted, occurring a reduction of latencies with age increase. We verified that maturation of wave I was faster and the maturation of wave V was slower. We could perceive that the maturation of the auditory pathway up to the brainstem follows the caudorostral direction, being the peripheral pathway more precocious and the rostral pathway more delayed. Conclusion: Based on the findings of this study, we recommend the application of the audiological evaluation procedure using BAEP in preterm children, at least until 20 months of age, by taking into account the gestational age in order to obtain reliable analyses.

A Cetamina, antagonista não competitivo de receptores de glutamato do tipo NMDA, é uma substância com propriedades dissociativas originalmente utilizada como anestésico que apresenta a característica de intensificar as experiências sensoriais. Apesar de seus conhecidos efeitos sobre os aspectos cognitivos e comportamentais, poucos estudos préclínicos foram conduzidos para tentar detectar os efeitos físicos e/ou comportamentais da abstinência de Cetamina após consumo prolongado. Partindo do princípio de que os efeitos da Cetamina sobre a neurotransmissão glutamatérgica induzem alguns dos sintomas observados durante surtos esquizofrênicos, como as alucinações auditivas, e sabendo que o colículo inferior tem sua função ligada ao processamento da informação sensorial a estímulos sonoros, neste estudo avaliamos os efeitos da modulação glutamatérgica na área cortical pré-límbica (PrL) sobre os potenciais evocados auditivos eliciados (PEAs) no colículo inferior. As medidas foram realizadas no fim do tratamento, ou seja, no 14° dia, 24 horas e 6 dias após a retirada da cetamina. Em nossos resultados obtivemos que a administração local de NMDA, foi capaz de diminuir a amplitude dos PEAs, os quais foram recuperados 24 horas após. A cetamina sistêmica não foi capaz de diminuir os PEAs, uma provável consequência da interação com outros receptores além do NMDA. Os testes realizados 6 dias após a interrupção ao tratamento crônico de cetamina, demonstraram uma forma inesperada de U, diferente da curva padrão de U invertido. Além disso, encontramos que as alterações provocadas pela cetamina são dependentes dos níveis dos mecanismos dopaminérgico e glutamatérgicos. Estes resultados demonstram que o processamento auditivo no colículo inferior está sob controle direto no Pré límbico e permitem ampliar o conhecimento atual da neurobiologia por evidenciar novas informações do efeito crônico da cetamina. / Ketamine is a non-competitive NMDA receptor antagonist. It is a substance with dissociative properties originally used as anesthetic, which can intensify sensory experiences, being also capable of accentuating the psychotic state in patients with schizophrenia. Despite its known effect on cognitive aspects and behavior, there are few preclinical studies conducted to identify physical and behavioral effects of ketamine withdrawal after its long-term use. Moreover, little is known about the impact of repetitive use of ketamine on brain structures and their functioning. The inferior colliculus, part of the midbrain tectum, is mainly related to auditory information processing, sending information to the motor centers and participating in the modulation and expression of specific behaviors, such as attack and predatory. Therefore, it is related to the biological importance of sounds to survival. The auditory hallucinations induced by schizophrenic psychotic crisis has as neural correspondent the activation of inferior colliculus and cortical areas. It is not yet known which cortical area is connected to the modulation of alterations induced by electrophysiological potential registered in inferior colliculus. Considering that the effects of ketamine on glutamate neurotransmission induces the symptoms observed during schizophrenic psychotic crisis, such as auditory hallucinations, and that inferior colliculus is related to the sensory information processing and auditory pathways, the present work evaluates the effects of glutamate modulation on pre-limbic cortical area on auditory evoked potential startle in inferior colliculus of rats tested during and after interruption of chronic treatment with ketamine

INTRODUÇÃO: Os Potenciais Evocados Auditivos avaliam a atividade neuroelétrica da via auditiva desde o nervo auditivo até o córtex cerebral. A vectoeletronistagmografia permite analisar os canais semicirculares e/ou nervo vestibular inferior, verificando se existe comprometimento vestibular periférico ou central. A reabilitação vestibular é composta de exercícios físicos ativos e repetitivos de olhos, cabeça e corpo e/ou manobras específicas que visam diminuir a tontura e a instabilidade corporal, aumentar a estabilização no olhar, o controle postural e melhorar o bem-estar na realização das atividades do diaa- dia. Levando-se em conta a escassez de trabalhos na literatura que investiguem a via auditiva central em indivíduos com síndrome vestibular periférica e que sejam submetidos à reabilitação vestibular, torna-se importante conhecer o funcionamento do sistema auditivo central, desde o tronco encefálico até o córtex auditivo, em indivíduos com vestibulopatias periféricas. OBJETIVOS: caracterizar os potenciais evocados auditivos de curta, média e longa latências em indivíduos com vestibulopatias periféricas, bem como verificar a evolução destes potenciais e dos resultados obtidos no Dizziness Handicap Inventory (DHI) frente à reabilitação vestibular. MÉTODOS: Foram submetidos à avaliação eletrofisiológica da audição por meio dos potenciais evocados auditivos de tronco encefálico (PEATE), potencial evocado auditivo de média latência (PEAML) e potencial cognitivo (P300), bem como à aplicação do questionário DHI, antes e após reabilitação vestibular, 20 indivíduos com diagnóstico de Síndrome Vestibular Periférica Irritativa (SVPI) e 17 indivíduos com diagnóstico de Síndrome Vestibular Periférica Deficitária (SVPD), com idades entre 20 e 70 anos. RESULTADOS: Os resultados demonstraram que o grupo com SVPD apresentou maior porcentagem de resultados alterados no PEATE e PEAML. No que diz respeito aos tipos de alterações, pode-se observar no grupo com SVPD, alteração em tronco encefálico baixo no PEATE pré e pós RV; aumento das latências das ondas Na e Pa no PEAML pós RV, aumento da latência da onda Pa pré RV e efeito eletrodo para a amplitude Na- Pa pós RV. No grupo com SVPI, foi observada alteração do tipo outros no PEATE pré RV; aumento da latência da onda Pa no PEAML pré e pós RV e ambas as alterações para a amplitude Na-Pa pós RV. No estudo da evolução dos resultados pré e pós RV, pode-se observar maior porcentagem de resultados semelhantes para os três potenciais, em ambos os grupos avaliados. Na comparação do DHI pré e pós RV, ocorreram melhores resultados para os aspectos físico, emocional e funcional no grupo com SVPI e para os aspectos físico e emocional no grupo com SVPD. Tornam-se necessários mais estudos que avaliem a via auditiva central destes indivíduos para uma melhor caracterização dos achados eletrofisiológicos / INTRODUCTION: The auditory evoked potentials assess the neuroelectrical activity of the auditory pathway from the auditory nerve to the cerebral cortex. The vectoelectronystagmography analyzes the semicircular canals and/or inferior vestibular nerve, checking peripheral or central vestibular involvement. The vestibular rehabilitation therapy consists in active exercises and repetitive eyes exercises, head and body and/or specific maneuvers to reduce the dizziness and body instability, increase gaze stability and postural control and also improve well-being in daily activities. Taking into account the scarcity of studies in the literature that investigate the central auditory pathways in subjects who underwent vestibular rehabilitation therapy, it becames important to know the central auditory system from the brainstem to the auditory cortex, in subjects with peripheral vestibular disorders. OBJECTIVE: To characterize the auditory evoked potentials of short, middle and long latencies in subjects with peripheral vestibular disorders, as well as to evaluate the development of these potentials and the results obtained in the Dizziness Handicap Inventory (DHI) after vestibular rehabilitation therapy (VRT). METHODS: brainstem auditory evoked potential (BAEP), Auditory Middle- Latency Response (AMLR), cognitive potential (P300) and DHI were carried out in 20 subjects with Peripheral Vestibular Hyperfunction Syndrome and 17 subjects with Peripheral Vestibular Hypofunction Syndrome, aged between 20 and 70, before and after vestibular rehabilitation therapy. RESULTS: The results showed that the Peripheral Vestibular Hypofunction Syndrome group, presented higher percentage of altered results on BAEP and AMLR. Comparing the normal and altered results (qualitative analysis) between the groups in the BAEP, lower brainstem was predominantly observed in the Peripheral Vestibular Hypofunction Syndrome group before and after VRT; increased latencies of Na and Pa waves in AMLR after VRT, incresead latency of Pa wave in AMLR before VRT and electrode effect to the Na-Pa amplitude after VRT. The alteration predominantly observed in the Peripheral Vestibular Hyperfunction Syndrome group, was the other type one before VRT; increased latency of Pa wave in AMLR before and after VRT and both changes to the Na-Pa amplitude after VRT. In the study of the evolution before and after VRT, it was observed a higher percentage of similar results for the three potentials in both groups. Comparing results before and after VRT, the DHI greatest improvement occurred for the physical, emotional and functional aspects in the Peripheral Vestibular Hyperfunction Syndrome group and for the physical and emotional aspects in the Peripheral Vestibular Hypofunction Syndrome group. Further studies that evaluate the central auditory pathway of individuals with peripheral vestibular syndrome are needed to better characterize the electrophysiological findings

Os potenciais evocados auditivos de tronco encefálico (PEATE) são um instrumento clínico muito útil na avaliação da maturação das vias auditivas em crianças nascidas pré-termo. Objetivos: Observar a maturação da via auditiva pela análise PEATE em crianças nascidas prétermo em três idades (4, 12 e 20 meses de idade). Casuística e Método: Coorte, individual, observacional, comparativo e contemporâneo. O fator em estudo foi crianças nascidas pré-termo e o desfecho à observação da maturação da via auditiva neste grupo, pela análise PEATE, em três avaliações (aos 4, 12 e 20 meses de idade), precedido de avaliação otorrinolaringológica e audiológica com objetivo de garantir que não apresentavam alteração auditiva. Resultados: Ingressaram 73 crianças pré-termo. Não foi encontrada diferença estatística (P>0,05) na comparação dos resultados entre os gêneros, bem como interaural. Houve diferença estatiticamente significante entre idade gestacional, as latências absolutas e intervalos interpicos nas três avaliações realizadas, ocorrendo uma diminuição das latências com o aumento da idade. Verificamos que a maturação da onda I foi mais rápida, e a maturação da onda V foi mais lenta. Podemos perceber que a maturação da via auditiva até o tronco encefálico segue o sentido caudorostral, sendo a da via periférica mais precoce, e a da rostral, mais tardia. Conclusão: Com base nos achados deste estudo, recomendamos que a aplicação do procedimento de avaliação audiológica através do PEATE em crianças nascidas pré-termo, pelo menos até os 20 meses de idade, seja realizado levando-se em conta a idade gestacional a fim de se obter análises fidedignas. / Brainstem Auditory Evoked Potential (BAEP) is a very useful clinical instrument in the evaluation of the auditory pathways maturation in preterm children. Objective: To observe the maturation of the auditory pathway with the use of the BAEP analysis in preterm children at three different ages (four, 12 and 20 months). Casuistry and Method: Group, individual, observational, comparative and contemporary. Preterm children and the outcome to observation of the auditory pathway maturation by the BAEP analysis in three evaluations (at 4, 12 and 20 months of age) were studied. The procedures were preceded by otolaryngological and auditory evaluation with the objective to guarantee the non presence of auditory alteration. Results: Seventy-three preterm children participated in the study. Statistically significant difference was not found (P> 0,05) in the comparison between genders and between ears. There was a statistically significant difference among gestational ages, absolute latencies and interpic intervals in the three evaluations conducted, occurring a reduction of latencies with age increase. We verified that maturation of wave I was faster and the maturation of wave V was slower. We could perceive that the maturation of the auditory pathway up to the brainstem follows the caudorostral direction, being the peripheral pathway more precocious and the rostral pathway more delayed. Conclusion: Based on the findings of this study, we recommend the application of the audiological evaluation procedure using BAEP in preterm children, at least until 20 months of age, by taking into account the gestational age in order to obtain reliable analyses.

Medimos a acuidade visual em crianças com paralisia cerebral do tipo espástica, classificadas em tetraplégicas, diplégicas e hemiplégicas, de acordo com o seu prejuízo motor, pelo método dos potenciais visuais evocados de varredura. Encontramos uma redução na acuidade visual em todos as crianças com tetraplegia e diplegia e em 94% das crianças com hemiplegia. Ambliopia foi identificada em 16% das crianças. Uma alta correlacão entre o prejuízo motor e a redução da acuidade visual foi encontrada para todas as classes. Concluímos que a acuidade visual está reduzida na paralisia cerebral espástica e que esta é de origem cortical, uma vez que o exame oftalmológico de todas as crianças era normal. / We measured the visual acuity in children with spastic cerebral palsy classified as tetraplegic, diplegic and hemiplegic according to their motor impairment by the sweep visual evoked potential method. We found a reduction in the visual acuity of all tetraplegic and diplegic and in 94% of the hemiplegic children. Ambliopia was found in 16% of children. A high correlation was found between the motor impairment and the reduction in the visual acuity. We conclude that the visual acuity was reducted in the spastic cerebral palsy and the origins are presumed to be cortical since the ophthalmological exam in all children was normal.

Transcranial magnetic stimulation (TMS) is a 37-year-old non-invasive tool and can be used for diagnostic, therapeutics, and research purposes. In research, TMS is mostly used to stimulate the motor cortex, resulting in a neuroelectric excitatory response called a motor evoked potential (MEP). The resulting nerve signal leads to muscle movement, which can be measured by electromyography (EMG). Majority of previous research has targeted muscles of the upper limbs, due to the relative inaccessibility of the cortical leg area. Thus, the aim of this study is to investigate whether asymmetry occurs during lower limb stimulation and if there is a difference in stimulated muscles between dominant and non-dominant leg. Nine healthy adults conducted cortical stimulation over the motor cortex using double cone coil. EMG was recorded from the rectus femoris, tibialis anterior and abductor hallucis on both left and right leg. Depending on the subject's tolerance, data was collected by delivering 30 or 35 pulses. For each intensity, five MEPs were recorded, starting at 30% of the intensity and increasing in steps of 10%. Results showed no significant difference (p>0,05) between the dominant and non-dominant leg in all three muscles. In conclusion, the study no stimulus response asymmetry between the dominant and non-dominant leg in the respective muscle.

Introduction: Somatosensory evoked potentials (SSEP) play a pivotal role in the diagnosis and disease monitoring of multiple sclerosis (MS). Delayed latencies are a surrogate for demyelination along the sensory aerence. This study aimed to evaluate if SSEP latencies are representative of demyelination of the brain overall, by correlating with cerebral microstructural integrity as measured by Magnetic resonance (MR) diusion tensor imaging (DTI). Analysis was performed in a hypothesis-free whole brain approach using tract-based spatial statistics (TBSS). Material and methods: A total of 46 patients with MS or clinically isolated syndrome were included in the study. Bilateral SSEPs of the median nerve measuring mean N20 latencies (mN20) and Central Conduction Time (CCT), were acquired. MRI scans were performed at 3T. DTI acquisition was done with a single-shot echoplanar imaging technique with 80 diusion directions. The FSL software package was used to process the DTI datasets and to calculate maps of fractional anisotropy (FA), axial diusivity (AD), and radial diusivity (RD). These maps were then further analyzed using the TBSS module. The mean N20 and CCT and the right- and left-sided N20 and CCT were separately correlated to FA, AD, and RD, controlled for age, gender, and EDSS as variables of non-interest. Results: Widespread negative correlations of SSEP latencies with FA (p = 0.0005) and positive correlations with RD (p = 0.0003) were measured in distinct white matter tracts, especially the optic tracts, corpus callosum, and posterior corona radiata. No correlation with AD was found in any white matter tract. Conclusion: Highly significant correlations of FA and RD to SSEPs suggest that their latency is representative of widespread microstructural change, and especially demyelination in patients suering from MS, reaching beyond the classic somatosensory regions. This points to the usefulness of SSEPs as a non-invasive tool in the evaluation of microstructural damage to the brain.

Le traitement de l’épilepsie chez le jeune enfant représente un enjeu majeur pour le développement de ce dernier. Chez la grande majorité des enfants atteints de spasmes infantiles et chez plusieurs atteints de crises partielles complexes réfractaires, le vigabatrin (VGB) représente un traitement incontournable. Cette médication, ayant démontré un haut taux d’efficacité chez cette population, semble toutefois mener à une atteinte du champ visuel périphérique souvent asymptomatique. L’évaluation clinique des champs visuels avec la périmétrie chez les patients de moins de neuf ans d’âge développemental est toutefois très difficile, voire impossible. Les études électrophysiologiques classiques menées auprès de la population épileptique pédiatrique suggèrent l’atteinte des structures liées aux cônes de la rétine. Les protocoles standards ne sont toutefois pas spécifiques aux champs visuels et les déficits soulignés ne concordent pas avec l’atteinte périphérique observée. Cette thèse vise donc à élaborer une tâche adaptée à l’évaluation des champs visuels chez les enfants en utilisant un protocole objectif, rapide et spécifique aux champs visuels à partir des potentiels évoqués visuels (PEVs) et à évaluer, à l’aide de cette méthode, les effets neurotoxiques à long terme du VGB chez des enfants épileptiques exposés en bas âge. La validation de la méthode est présentée dans le premier article. La stimulation est constituée de deux cercles concentriques faits de damiers à renversement de phase alternant à différentes fréquences temporelles. La passation de la tâche chez l’adulte permet de constater qu’une seule électrode corticale (Oz) est nécessaire à l’enregistrement simultané des réponses du champ visuel central et périphérique et qu’il est possible de recueillir les réponses électrophysiologiques très rapidement grâces l’utilisation de l’état-stationnaire (steady-state). La comparaison des données d’enfants et d’adultes normaux permet de constater que les réponses recueillies au sein des deux régions visuelles ne dépendent ni de l’âge ni du sexe. Les réponses centrales sont aussi corrélées à l’acuité visuelle. De plus, la validité de cette méthode est corroborée auprès d’adolescents ayant reçu un diagnostic clinique d’un déficit visuel central ou périphérique. En somme, la méthode validée permet d’évaluer adéquatement les champs visuels corticaux central et périphérique simultanément et rapidement, tant chez les adultes que chez les enfants. Le second article de cette thèse porte sur l’évaluation des champs visuels, grâce à la méthode préalablement validée, d’enfants épileptiques exposés au VGB en jeune âge en comparaison avec des enfants épileptiques exposés à d’autres antiépileptiques et à des enfants neurologiquement sains. La méthode a été bonifiée grâce à la variation du contraste et à l’enregistrement simultané de la réponse rétinienne. On trouve que la réponse corticale centrale est diminuée à haut et à moyen contrastes chez les enfants exposés au VGB et à haut contraste chez les enfants exposés à d’autres antiépileptiques. Le gain de contraste est altéré au sein des deux groupes d’enfants épileptiques. Par contre, l’absence de différences entre les deux groupes neurologiquement atteints ne permet pas de faire la distinction entre l’effet de la médication et celui de la maladie. De plus, la réponse rétinienne périphérique est atteinte chez les enfants épileptiques exposés au Sabril® en comparaison avec les enfants neurologiquement sains. La réponse rétinienne périphérique semble liée à la durée d’exposition à la médication. Ces résultats corroborent ceux rapportés dans la littérature. En somme, les résultats de cette thèse offrent une méthode complémentaire, rapide, fiable, objective à celles connues pour l’évaluation des champs visuels chez les enfants. Ils apportent aussi un éclairage nouveau sur les impacts à long terme possibles chez les enfants exposés au VGB dans la petite enfance. / Epilepsy control is a major issue for the normal development in children. For the vast majority of children with infantile spasms and for some with refractory complex partial seizures, vigabatrin (VGB) represents the main treatment. VGB, which have shown high efficiency rate in this population, may, however, induce a peripheral visual field deficit, often asymptomatic. Clinical visual field assessment with perimetry is practically impossible in patients less than nine years of developmental age. Electrophysiological studies in epileptic children suggest an impact on the retinal structures related to the cones. However, standard protocols are not field-specific and the deficits reported in the literature are not coherent with the peripheral deficit observed. Thus, this thesis aims to develop a fast and efficient electrophysiological protocol to examine the visual field’s integrity, which would be useful in pediatric testing and to assess the visual field long-term effects of the VGB in school-aged epileptic children exposed early in life. The first article concerns the method’s validation. The stimulation is made of two high-contrast radial checks reversing at two different temporal frequencies. Adult testing reveals that only one electrode (Oz) is needed to record simultaneously both central and peripheral visual fields and that steady-state use allows fast gathering of both electrophysiological responses. No effect of age or sex was found in the comparison of adult and child’ responses. Moreover, the visual acuity, as calculated by the binocular visual acuity index, was related to the central signal when comparing healthy participants with central visual impaired adolescents. Our method presents several advantages in evaluating visual fields integrity, as it is fast, reliable and efficient, and applicable in children. The aim of the second article of the thesis is the assessment of the long term visual effect on the visual field in children exposed to VGB in infancy in comparison to epileptic children exposed to other antiepileptics and with healthy children using the previously validated electrophysiology method with the addition of contrast variation and simultaneous recording of electroretinograms. Results reveal a cortical central deficit at high and mid-range contrast in VGB exposed-children and at high contrast in other antiepileptic exposed group. The contrast gain is also affected in both epileptic groups. The absence of difference between both epileptic groups does not allow distinguishing the impact of medication and/or seizure disorder. The peripheral retinal response is also altered in the VGB-exposed group in comparison to the healthy group. The peripheral retinal response is related to the exposition duration. This result concurs with previous studies in the literature. Finally, the results of the thesis offer an objective, fast, efficient and alternative method to assess visual fields in children. They also bring a new point of view on the likely long term impacts of the VGB in children exposed in infancy.

Objetivo: Determinar as mudanças nas ondas dos potenciais evocados auditivos de tronco encefálico (PEATE) como indicador de integridade neural em eventos de hipoxia-isquemia cerebral em crianças submetidas à cirurgia cardíaca com circulação extracorpórea (CEC). Método: Participaram deste estudo 09 pacientes pediátricos com idade entre 0 a 2 anos, submetidos à cirurgia cardíaca de alta complexidade no Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto. A avaliação eletrofisiológica da audição foi realizada no centro cirúrgico do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, durante os respectivos momentos da cirurgia cardíaca: Sedação, Circulação Extracorpórea (CEC) e Hipotermia, e ao Final da Cirurgia, com o registro do potencial evocado auditivo de tronco encefálico (PEATE), por meio do equipamento Nicolet Endeavor CR, conectado a um notebook, duas sondas de espuma, 4 eletrodos de agulha, posicionados na mastóide direita e esquerda, vertex craniano e fronte. Resultados: As crianças tinham média de idade de 10 meses. Dessas 9 crianças, 3 do sexo feminino e 6 do sexo masculino, a média do peso foi de 6,0 Kg, as patologias e ou propostas cirúrgicas foram: Correção de Disfunção Valvar Aórtica e Tricúspide por Valvoplastia, Correção de Drenagem Anômola Total das Veias Pulmonares, Correção de Cor Triatriatum, Operação de Glenn, Implante de Marcapasso Cardíaco Intracavitário de Dupla Câmara, Correção de Disfunção Valvar Mitral por Valvoplastia, Fechamento de Comunicação Interatrial, Fechamento de Comunicação Interventricular, Bandagem e Correção da Persistência Canal Arterial. Duas dessas crianças possuem Síndrome de Down. Foi observado quanto às latências das ondas I, III e V, e seus interpicos da orelha direita e esquerda mudanças dos valores comparadas ao início com CEC e hipotermia, assim como ao início com o final da cirurgia, porém os valores foram estatisticamente não significantes, p > 0,05. Conclusão: Não foram encontradas alterações nas latências absolutas e na latência dos intervalos interpicos do PEATE para as situações de hipotermia e circulação extracorpórea. / Objective: To determine changes in the waves of brainstem evoked response audiometry (BERA) as an indicator of neural integrity in events of brain hypoxiaischemia in children undergoing cardiac surgery with cardiopulmonary bypass (CPB). Method: 09 pediatric patients aged 0 to 2 have taken part in this study, who were submitted to highly complex cardiac surgery at Hospital das Clínicas, Medical School of Ribeirão Preto. The electrophysiological assessment of hearing was performed at the surgical center of Hospital das Clínicas of the Medical School of Ribeirão Preto, during the respective moments of the cardiac surgery: Sedation, Extracorporeal Circulation (CPB) and Hypothermia, and at the End of Surgery, by recording the brainstem auditory evoked response (BERA), using the Nicolet Endeavor CR equipment, connected to a laptop, two foam probes, four needle electrodes positioned in the right and left mastoid, cranial vertex and forehead. Results: The mean age of the children was 10 months. Out of these 9 children, 3 were female and 6 were male, and their mean weight was 6.0 kg. The pathologies and or surgical proposals were: Correction of Aortic Valve Dysfunction and Tricuspid by valvuloplasty, Correction of total anomalous pulmonary venous drainage, Color Correction Triatriatum, Glenn Procedure, Double-chambered Intracavitary Cardiac Pacemaker Implantation, Mitral Valve Dysfunction Correction, Interatrial Communication Closure, Interventricular Communication Closure, Bandaging, and Correction of Persistent Arterial Canal. Two of these children have Down Syndrome. As for the latencies of the I, III and V waves and their interpeaks of the right and left ear, it was observed changes in values compared to the onset with CPB and hypothermia, as well as to the beginning with the end of surgery, but the values were not statistically significant, p > 0.05. Conclusion: No alterations were found in the absolute latencies and in the latency of the BERA intervals for situations of hypothermia and cardiopulmonary bypass.