Dual role of the nasal microbiota in neurological diseases—An unignorable risk factor or a potential therapy carrier

Recently, comparative studies have rapidly increased with the closer correlation between microbiota and neurological diseases. However, most insights about the association between microbiota and neurological diseases still focus on the gut-brain axis and ignore that nasal microbiota could form a complex and essential link with the nervous system via the nose-to-brain pathway, suggesting the role in modulating the immune system, metabolic system, and nervous system development, which influence the physiopathology of neurological diseases. Due to the complex interactions between nasal microbiota and the brain, the nasal microbiota may have a particular pathogenic effect and therapeutic potential on neurological diseases. Therefore, this review aims to deeply analyze the dual effects of nasal microbiota on neurological diseases, focusing on pathogenic and therapeutic effects to provide a new perspective for preventing and treating neurological diseases by altering nasal microbiota. This review concludes the bidirectional effects of nasal microbiota on neurological diseases, including the pathogenicity and potential treatment on Alzheimer's disease, Parkinson's disease, Multiple sclerosis, and Stroke. Furthermore, modern medical technology combined with artificial intelligence, including implantable sensors, modeling software, and nanofluid techniques, may further study the complex effects between nasal microbiota and the brain, thereby providing new options for treating neurological diseases.