Simonini Ludovica, Frijia Francesca, Ait Ali Lamia, Foffa Ilenia, Vecoli Cecilia, De Gori Carmelo, De Cori Sara, Baroni Monica, Aquaro Giovanni Donato, Maremmani Carlo, Lombardo Francesco
Institute of Clinical Physiology, National Research Council (CNR), 54100 Massa, Italy.
Bioengineering Unit, Fondazione Toscana G. Monasterio, 56124 Pisa, Italy.
Diagnostics (Basel). 2024 Feb 7;14(4):359. doi: 10.3390/diagnostics14040359.
Olfactory dysfunction (OD) is one of the most common symptoms in COVID-19 patients and can impact patients' lives significantly. The aim of this review was to investigate the multifaceted impact of COVID-19 on the olfactory system and to provide an overview of magnetic resonance (MRI) findings and neurocognitive disorders in patients with COVID-19-related OD. Extensive searches were conducted across PubMed, Scopus, and Google Scholar until 5 December 2023. The included articles were 12 observational studies and 1 case report that assess structural changes in olfactory structures, highlighted through MRI, and 10 studies correlating the loss of smell with neurocognitive disorders or mood disorders in COVID-19 patients. MRI findings consistently indicate volumetric abnormalities, altered signal intensity of olfactory bulbs (OBs), and anomalies in the olfactory cortex among COVID-19 patients with persistent OD. The correlation between OD and neurocognitive deficits reveals associations with cognitive impairment, memory deficits, and persistent depressive symptoms. Treatment approaches, including olfactory training and pharmacological interventions, are discussed, emphasizing the need for sustained therapeutic interventions. This review points out several limitations in the current literature while exploring the intricate effects of COVID-19 on OD and its connection to cognitive deficits and mood disorders. The lack of objective olfactory measurements in some studies and potential validity issues in self-reports emphasize the need for cautious interpretation. Our research highlights the critical need for extensive studies with larger samples, proper controls, and objective measurements to deepen our understanding of COVID-19's long-term effects on neurological and olfactory dysfunctions.
嗅觉功能障碍（OD）是新冠病毒感染患者最常见的症状之一，会对患者生活产生重大影响。本综述旨在研究新冠病毒对嗅觉系统的多方面影响，并概述新冠病毒相关嗅觉功能障碍患者的磁共振成像（MRI）结果及神经认知障碍。截至2023年12月5日，我们在PubMed、Scopus和谷歌学术上进行了广泛检索。纳入的文章包括12项观察性研究和1例病例报告，这些研究评估了通过MRI突出显示的嗅觉结构的结构变化，以及10项将新冠病毒患者嗅觉丧失与神经认知障碍或情绪障碍相关联的研究。MRI结果一致表明，患有持续性嗅觉功能障碍的新冠病毒患者存在体积异常、嗅球（OB）信号强度改变以及嗅觉皮质异常。嗅觉功能障碍与神经认知缺陷之间的相关性揭示了其与认知障碍、记忆缺陷和持续性抑郁症状的关联。文中讨论了包括嗅觉训练和药物干预在内的治疗方法，强调了持续治疗干预的必要性。本综述指出了当前文献在探索新冠病毒对嗅觉功能障碍的复杂影响及其与认知缺陷和情绪障碍的联系方面存在的若干局限性。一些研究缺乏客观的嗅觉测量，自我报告中存在潜在的有效性问题，这强调了谨慎解读的必要性。我们的研究强调，迫切需要进行更大样本、适当对照和客观测量的广泛研究，以加深我们对新冠病毒对神经和嗅觉功能障碍长期影响的理解。
