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Surdez induzida por exposição sonora
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Resumo(s)
A perda auditiva por exposição sonora é a segunda forma mais comum de défice auditivo neuro-sensorial, sendo comum em contexto ocupacional e também ao nível do lazer. O impacto que tem na nossa qualidade de vida não é imediato, mas tem uma grande repercussão na nossa saúde a longo prazo, e não apenas ao nível da audição. Nos últimos anos tem-se constatado que o elemento mais vulnerável à exposição excessiva será a sinapse entre as células ciliadas e o nervo coclear, e que o dano (associado à excitotoxicidade por glutamato) sofrido terá um início ainda mais precoce e insidioso, não detectado no audiograma excepto quando já existe um grau elevado de audição comprometida. Este será selectivo a um grupo restrito de fibras importantes na discriminação de discurso em ambientes ruidoso, ao qual esta entidade está clinicamente associada. Mesmo quando as exposições revelam apenas alterações transitórias no audiograma, pode já ter havido dano neuronal irreversível. Por outro lado, o efeito do som pode ser facilmente exponenciado por outros factores, como substâncias químicas, seja em contexto ocupacional ou por fármacos. Não existe tratamento eficaz. Poucos fármacos possuem estudos em humanos, e revelam eficácia ou protecção bastante limitada. A atenção tem sido virada para o uso de células estaminais e neurotrofinas, que têm demonstrado resultados promissores, ainda que apenas em ratos. Actualmente, a medida mais eficaz passa pela prevenção e sensibilização da população para a protecção contra a exposição excessiva.
Noise-induced hearing loss is the second most common auditive neurosensorial deficit, being easily found both in occupational and recreational settings. Its impact in our lives is not immediate, but its repercussions on the long run can be heavy, and not only regarding our hearing. Recently, it has been noted that the most vulnerable element to excessive sound exposure are not the hair cells, but their synaptic connection with the cochlear nerve. The setting of the damage (which has been associated with glutamate excitotoxicity) is insidious and believed to occur earlier than previously thought. Such effects are only picked out on an audiogram when the hearing is severely compromised. Research indicates that the damage is selective towards a restricted group of nerve fibers essential to speech discrimination in noisy environments, which is compromised in people with this disorder. Nerve damage can exist even when the audiogram only reveals transitory threshold shifts. Moreover, the deleterious effect of sound exposure can be furthered by another ototoxic substances, such as chemicals used in occupational settings and medications. So far, there is no treatment. A limited number of drugs have been studied in humans and reveal limited effectiveness or grant restricted protection. Lately, attention has been brought upon the use of stem cells and neurotrophins, which have exhibited promising results, albeit only in studies conducted in mice. Currently, prevention and awareness raising remain the cornerstone in the struggle against the consequences of noise-induced hearing loss.
Noise-induced hearing loss is the second most common auditive neurosensorial deficit, being easily found both in occupational and recreational settings. Its impact in our lives is not immediate, but its repercussions on the long run can be heavy, and not only regarding our hearing. Recently, it has been noted that the most vulnerable element to excessive sound exposure are not the hair cells, but their synaptic connection with the cochlear nerve. The setting of the damage (which has been associated with glutamate excitotoxicity) is insidious and believed to occur earlier than previously thought. Such effects are only picked out on an audiogram when the hearing is severely compromised. Research indicates that the damage is selective towards a restricted group of nerve fibers essential to speech discrimination in noisy environments, which is compromised in people with this disorder. Nerve damage can exist even when the audiogram only reveals transitory threshold shifts. Moreover, the deleterious effect of sound exposure can be furthered by another ototoxic substances, such as chemicals used in occupational settings and medications. So far, there is no treatment. A limited number of drugs have been studied in humans and reveal limited effectiveness or grant restricted protection. Lately, attention has been brought upon the use of stem cells and neurotrophins, which have exhibited promising results, albeit only in studies conducted in mice. Currently, prevention and awareness raising remain the cornerstone in the struggle against the consequences of noise-induced hearing loss.
Descrição
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2019
Palavras-chave
Perda auditiva por exposição sonora Sinaptopatia coclear Ototoxicidade Prevenção Tratamento Otorrinolaringologia