Abstract：
An altered sense of smell and taste was recognized as one of the most characteristic symptoms of coronavirus infection disease (COVID-19). Despite most patients experiencing a complete functional resolution, there is a 21.3% prevalence of persistent alteration at 12 months after infection. To date, magnetic resonance imaging (MRI) findings in these patients have been variable and not clearly defined. We aimed to clarify radiological alterations of olfactory pathways in patients with long COVID-19 characterized by olfactory dysfunction. A comprehensive review of the English literature was performed by analyzing relevant papers about this topic. A case series was presented: all patients underwent complete otorhinolaryngology evaluation including the Sniffin\' Sticks battery test. A previous diagnosis of SARS-CoV-2 infection was confirmed by positive swabs. The MRIs were acquired using a 3.0T MR scanner with a standardized protocol for olfactory tract analysis. Images were first analysed by a dedicated neuroradiologist and subsequently reviewed and compared with the previous available MRIs. The review of the literature retrieved 25 studies; most cases of olfactory dysfunction more than 3 months after SARS-CoV-2 infection showed olfactory bulb (OB) reduction. Patients in the personal case series had asymmetry and a reduction in the volume of the OB. This evidence was strengthened by the comparison with a previous MRI, where the OBs were normal. The results preliminarily confirmed OB reduction in cases of long COVID-19 with an altered sense of smell. Further studies are needed to clarify the epidemiology, pathophysiology and prognosis.
摘要：
嗅觉和味觉的改变被认为是冠状病毒感染疾病(COVID-19)最典型的症状之一。尽管大多数患者经历了完整的功能消退，感染后12个月持续改变的患病率为21.3%.迄今为止,这些患者的磁共振成像(MRI)检查结果是可变的,并且没有明确定义.我们旨在阐明以嗅觉功能障碍为特征的长COVID-19患者嗅觉通路的放射学改变。通过分析有关该主题的相关论文，对英语文献进行了全面的回顾。提供了一系列病例：所有患者均接受了完整的耳鼻咽喉科评估，包括Sniffin\'Sticks电池测试。先前诊断为SARS-CoV-2感染通过阳性拭子证实。MRI是使用3.0TMR扫描仪获得的，该扫描仪具有用于嗅道分析的标准化方案。图像首先由专门的神经放射学家进行分析，随后进行审查并与以前可用的MRI进行比较。文献综述检索了25项研究；SARS-CoV-2感染后超过3个月的大多数嗅觉功能障碍病例显示嗅球（OB）减少。个人病例系列中的患者不对称且OB体积减少。通过与之前的MRI比较，这一证据得到了加强，OBs正常的地方。结果初步证实，嗅觉改变的长COVID-19病例的OB减少。需要进一步的研究来澄清流行病学，病理生理学和预后。
