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Advisor(s)
Abstract(s)
A surdez é uma patologia com grande prevalência mundial, com maior impacto nos países em desenvolvimento. As repercussões que esta tem verificam-se não só ao nível da relação com o ambiente e com os outros, mas também ao nível do próprio indivíduo, principalmente no cérebro.
O cérebro apresenta uma capacidade de plasticidade neuronal, sendo maior pouco após o nascimento decrescendo desde então, que, quando privado sensorialmente, permite a adaptação a uma realidade sem estímulos sensoriais auditivos. Assim, observamos que as áreas privadas de inputs são recrutadas por outras áreas sensoriais no processamento de estímulos, nomeadamente visuais e somatossensoriais. A esta capacidade de uma área utilizar outra que se encontrava inutilizada denominamos de plasticidade cross-modal.
Uma boa estimulação auditiva durante os primeiros anos de vida é essencial para a maturação do córtex auditivo. Desta forma existem diferenças em relação ao impacto da hipoacusia, especialmente a severa ou profunda, de acordo com a idade em que se instala. Assim, em idade pré-lingual, ou seja, aquela que ocorre antes do início da fala, constata-se uma maior plasticidade cross-modal visual e somatossensorial no córtex auditivo. Da mesma forma, em indivíduos com surdez pós-lingual severa a profunda também se verificou esta plasticidade, ainda que num grau mais ligeiro, pois a plasticidade nesta altura da vida é menor. Verificou-se ainda em adultos que quanto menor a gravidade da hipoacusia menor era a plasticidade cross-modal.
Os implantes cocleares permitem restaurar a audição em casos de surdez sensorial. No entanto, observamos uma grande variabilidade relativamente aos outcomes destes, que não pode ser explicada apenas por fatores pré-implantação.
Este Trabalho Final de Mestrado pretende rever os achados presentes na bibliografia e averiguar que impacto a plasticidade cross-modal pode ter nos outcomes dos implantes cocleares e se esta pode servir como prognóstico destes.
Deafness is a disease with a high world prevalence, especially in developing countries. The consequences of hypoacusia exists not only regarding the relationship of the individual and his surroundings, but also within the brain itself. When sensorially deprived, the brain has the capacity of neuronal plasticity. This capacity is higher right after birth, declining beyond this point with age, to adapt to the new reality without auditory stimuli. We also observe that the areas deprived in one sensorial modality are recruited by other sensorial areas of the brain, specially by visual and somatosensorial. To this ability of repurposing areas of the brain is what we define as cross-modal plasticity. Auditory stimulation in the early years of life is essential to the maturation of the auditory cortex. Indeed, there are differences in how hypoacusia impact the individual according to the it’s age of onset. In pre-lingually deafness – deafness before one is able to speak – we have greater visual and somatosensorial cross-modal plasticity in the auditory cortex. In the same fashion post-lingually deafness has evidence of cross-modal plasticity, although in a minor degree, due to a lesser capacity of neuronal plasticity. We also verified that adults that have a lower grade hypoacusia had less neuronal plasticity. Cochlear implants allow the restoration of auditory inputs in cases of sensorial deafness. However, there is a great variability in the outcomes of implantation that can’t be explained with just pre-implantation factors. This Master Thesis has the objective of reviewing the current bibliography related to this topic and analyzing the impact of cross-modal plasticity in the outcomes of cochlear implant and how it can work as a prognosis tool.
Deafness is a disease with a high world prevalence, especially in developing countries. The consequences of hypoacusia exists not only regarding the relationship of the individual and his surroundings, but also within the brain itself. When sensorially deprived, the brain has the capacity of neuronal plasticity. This capacity is higher right after birth, declining beyond this point with age, to adapt to the new reality without auditory stimuli. We also observe that the areas deprived in one sensorial modality are recruited by other sensorial areas of the brain, specially by visual and somatosensorial. To this ability of repurposing areas of the brain is what we define as cross-modal plasticity. Auditory stimulation in the early years of life is essential to the maturation of the auditory cortex. Indeed, there are differences in how hypoacusia impact the individual according to the it’s age of onset. In pre-lingually deafness – deafness before one is able to speak – we have greater visual and somatosensorial cross-modal plasticity in the auditory cortex. In the same fashion post-lingually deafness has evidence of cross-modal plasticity, although in a minor degree, due to a lesser capacity of neuronal plasticity. We also verified that adults that have a lower grade hypoacusia had less neuronal plasticity. Cochlear implants allow the restoration of auditory inputs in cases of sensorial deafness. However, there is a great variability in the outcomes of implantation that can’t be explained with just pre-implantation factors. This Master Thesis has the objective of reviewing the current bibliography related to this topic and analyzing the impact of cross-modal plasticity in the outcomes of cochlear implant and how it can work as a prognosis tool.
Description
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2020
Keywords
Surdez Córtex auditivo Plasticidade cross-modal Implante coclear Otorrinolaringologia