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Abstract(s)
A importância do olfato nos Humanos tem vindo a ser subestimada, talvez por
não ser percecionada como condição fatal. No entanto, esta alteração está associada a
inestimável perda de qualidade de vida. A associação entre envelhecimento e perda
olfativa tem-se demonstrado inevitável. Além disso, esta perda é também uma
característica central de doenças neurodegenerativas, como as Doenças de Parkinson e
Alzheimer.
Esta revisão bibliográfica tem como objetivo averiguar o estado da arte acerca
da consideração da disfunção olfativa como um biomarcador precoce de doença
neurodegenerativa, de progressão e de declínio cognitivo, com enfoque nas doenças de
Parkinson e Alzheimer.
Foi realizada uma pesquisa em bases de dados eletrónicas mediante as palavraschave “olfactory dysfunction”, “hyposmia”, “neurodegenerative disease”, “cognition” e
“dementia”, selecionando artigos de acordo com o Fator de Impacto e o Número de
Citações. Recorreu-se ainda a livros de referência na área.
A hiposmia é acompanhada por várias alterações estruturais periféricas e
centrais, e tende a manifestar-se anos antes dos sintomas motores e/ou cognitivos. No
caso da doença de Parkinson, dessas alterações destacam-se a acumulação de asinucleína no bulbo olfativo e de proteína-tau no núcleo olfativo anterior, associadas a
atrofia do bulbo, amígdala e córtex piriforme. Já na doença de Alzheimer destaca-se a
presença proeminente de emaranhados neurofibrilares e de amiloide-ß e, à semelhança
da doença de Parkinson, atrofia de estruturas centrais. Em ambas as doenças
verificam-se ainda alterações dos níveis de neurotransmissores, nomeadamente um
aumento dos neurónios dopaminérgicos periglomerulares, ainda que a disfunção
olfativa, na doença de Parkinson, não responda favoravelmente ao tratamento
dopaminérgico, pelo que outros neurotransmissores desempenharão um papel.
Desta forma, a disfunção olfativa poder-se-á estabelecer como um biomarcador
precoce de doença neurodegenerativa, e a aposta na sua deteção pode permitir o
diagnóstico precoce, e a possibilidade de adoção de uma estratégia preventiva, ou
mesmo possibilitar o desenvolvimento de terapêuticas modificadoras de doença, além
de permitir a possibilidade de deteção/acompanhamento de doentes em risco destas
doenças e de identificar aqueles com maior probabilidade de evolução para um estadio de demência ou mesmo a morte. No caso da doença de Parkinson, a hiposmia
apresenta-se ainda como possibilidade de poder estabelecer diagnóstico diferencial
com Parkinsonismo Atípico, enfatizando o seu valor.
Assim, conclui-se que o estudo olfativo é indispensável nos casos de doença
neurodegenerativa e acentua-se a necessidade de inclusão destes métodos de avaliação
na prática clínica, com um contributo inegável no que diz respeito à qualidade de vida
dos doentes, não esquecendo o impacto económico que daí poderá advir.
The importance of smell in humans has been underestimated, perhaps because it is not perceived as a fatal condition. However, this change is associated with an inestimable loss of quality of life. The association between aging and olfactory loss has been shown to be inevitable. Furthermore, this loss is also a central feature of neurodegenerative diseases such as Parkinson's and Alzheimer's Diseases. This literature review aims to investigate the state of the art regarding the consideration of olfactory dysfunction as an early biomarker of neurodegenerative disease, progression and cognitive decline, with a focus on Parkinson's and Alzheimer's diseases. A search was carried out in electronic databases using the keywords “olfactory dysfunction”, “hyposmia”, “neurodegenerative disease”, “cognition” and “dementia”, selecting articles according to the Impact Factor and the Number of Citations. It was also searched for reference books in the area. Hyposmia is accompanied by several peripheral and central structural changes, and tends to appear years before motor and/or cognitive symptoms. In the case of Parkinson's disease, the accumulation of a-synuclein in the olfactory bulb and tauprotein in the anterior olfactory nucleus stand out from these alterations, associated with atrophy of the bulb, amygdala and piriform cortex. In Alzheimer's disease, the prominent presence of neurofibrillary tangles and ß-amyloid is highlighted and, similarly to Parkinson's disease, atrophy of central structures is highlighted. In both diseases there are also changes in neurotransmitter levels, namely an increase in periglomerular dopaminergic neurons, although olfactory dysfunction in Parkinson's disease does not respond favorably to dopaminergic treatment, so other neurotransmitters may play a role. In this way, olfactory dysfunction can be established as an early biomarker of neurodegenerative disease, and the focus on its detection can allow early diagnosis, and the possibility of adopting a preventive strategy, or even enable the development of disease-modifying therapies, in addition to allowing the possibility of detecting/following up patients at risk for these diseases and identifying those most likely to progress to a stage of dementia or even death. In the case of Parkinson's disease, hyposmia is also a possibility to establish a differential diagnosis with Atypical Parkinsonism, emphasizing its value. Thus, it is concluded that the olfactory study is essential in cases of neurodegenerative disease and the need to include these assessment methods in clinical practice is emphasized, with an undeniable contribution regarding the quality of life of patients, not forgetting the economic impact that could result from this.
The importance of smell in humans has been underestimated, perhaps because it is not perceived as a fatal condition. However, this change is associated with an inestimable loss of quality of life. The association between aging and olfactory loss has been shown to be inevitable. Furthermore, this loss is also a central feature of neurodegenerative diseases such as Parkinson's and Alzheimer's Diseases. This literature review aims to investigate the state of the art regarding the consideration of olfactory dysfunction as an early biomarker of neurodegenerative disease, progression and cognitive decline, with a focus on Parkinson's and Alzheimer's diseases. A search was carried out in electronic databases using the keywords “olfactory dysfunction”, “hyposmia”, “neurodegenerative disease”, “cognition” and “dementia”, selecting articles according to the Impact Factor and the Number of Citations. It was also searched for reference books in the area. Hyposmia is accompanied by several peripheral and central structural changes, and tends to appear years before motor and/or cognitive symptoms. In the case of Parkinson's disease, the accumulation of a-synuclein in the olfactory bulb and tauprotein in the anterior olfactory nucleus stand out from these alterations, associated with atrophy of the bulb, amygdala and piriform cortex. In Alzheimer's disease, the prominent presence of neurofibrillary tangles and ß-amyloid is highlighted and, similarly to Parkinson's disease, atrophy of central structures is highlighted. In both diseases there are also changes in neurotransmitter levels, namely an increase in periglomerular dopaminergic neurons, although olfactory dysfunction in Parkinson's disease does not respond favorably to dopaminergic treatment, so other neurotransmitters may play a role. In this way, olfactory dysfunction can be established as an early biomarker of neurodegenerative disease, and the focus on its detection can allow early diagnosis, and the possibility of adopting a preventive strategy, or even enable the development of disease-modifying therapies, in addition to allowing the possibility of detecting/following up patients at risk for these diseases and identifying those most likely to progress to a stage of dementia or even death. In the case of Parkinson's disease, hyposmia is also a possibility to establish a differential diagnosis with Atypical Parkinsonism, emphasizing its value. Thus, it is concluded that the olfactory study is essential in cases of neurodegenerative disease and the need to include these assessment methods in clinical practice is emphasized, with an undeniable contribution regarding the quality of life of patients, not forgetting the economic impact that could result from this.
Description
Keywords
Cognição Demência Disfunção Olfativa Doença Neurodegenerativa Hiposmia