Abstract：
BACKGROUND: Patients with acquired, idiopathic olfactory dysfunction (OD) commonly undergo magnetic resonance imaging (MRI) evaluation to rule out intracranial pathologies. This practice is highly debated given the expense of MRI relative to the probability of detecting a treatable lesion. This, combined with the increasing use of MRI in research to investigate the mechanisms underlying OD, provided the impetus for this comprehensive review.
OBJECTIVE: The purpose of this systematic review was to both assess the utility of MRI in diagnosis of idiopathic OD and to describe MRI findings among mixed OD etiologies to better understand its role as a research tool in this patient population.
METHODS: A literature search of PubMed, Embase, Cochrane, Web of Science, and Scopus for studies with original MRI data for patients with OD was completed. Studies exclusively investigating patients with neurocognitive deficits or those studying traumatic or congenital etiologies of OD were excluded.
RESULTS: From 1758 candidate articles, 33 studies were included. Four studies reviewed patients with idiopathic OD for structural pathologies on MRI, of which 17 of 372 (4.6%) patients had a potential central cause identified, and 3 (0.8%) had an olfactory meningioma or olfactory neuroblastoma. Fourteen studies (42.4%) reported significant correlation between olfactory bulb volume and olfactory outcomes, and 6 studies (18.8%) reported gray matter volume reduction, specifically in the orbitofrontal cortex, anterior cingulate cortex, insular cortex, parahippocampal, and piriform cortex areas, in patients with mixed OD etiologies. Functional MRI studies reported reduced brain activation and functional connectivity in olfactory network areas.
CONCLUSIONS: MRI uncommonly detects intracranial pathology in patients with idiopathic OD. Among patients with mixed OD etiologies, reduced olfactory bulb and gray matter volume are the most common abnormal findings on MRI. Further research is required to better understand the role of MRI and its cost-effectiveness in patients with acquired, idiopathic OD.
OBJECTIVE: The purpose of this systematic review was to both assess the utility of MRI in diagnosis of idiopathic OD and to describe MRI findings among mixed OD etiologies to better understand its role as a research tool in this patient population.
METHODS: A literature search of PubMed, Embase, Cochrane, Web of Science, and Scopus for studies with original MRI data for patients with OD was completed. Studies exclusively investigating patients with neurocognitive deficits or those studying traumatic or congenital etiologies of OD were excluded.
RESULTS: From 1758 candidate articles, 33 studies were included. Four studies reviewed patients with idiopathic OD for structural pathologies on MRI, of which 17 of 372 (4.6%) patients had a potential central cause identified, and 3 (0.8%) had an olfactory meningioma or olfactory neuroblastoma. Fourteen studies (42.4%) reported significant correlation between olfactory bulb volume and olfactory outcomes, and 6 studies (18.8%) reported gray matter volume reduction, specifically in the orbitofrontal cortex, anterior cingulate cortex, insular cortex, parahippocampal, and piriform cortex areas, in patients with mixed OD etiologies. Functional MRI studies reported reduced brain activation and functional connectivity in olfactory network areas.
CONCLUSIONS: MRI uncommonly detects intracranial pathology in patients with idiopathic OD. Among patients with mixed OD etiologies, reduced olfactory bulb and gray matter volume are the most common abnormal findings on MRI. Further research is required to better understand the role of MRI and its cost-effectiveness in patients with acquired, idiopathic OD.
摘要：
背景：患者获得性，特发性嗅觉功能障碍（OD）通常接受磁共振成像（MRI）评估以排除颅内病变。考虑到相对于检测可治疗病变的概率的MRI的费用,这种实践是高度争论的。这个,结合在研究中越来越多地使用MRI来研究OD的潜在机制，为这次全面审查提供了动力。
目的：本系统评价的目的是评估MRI在特发性OD诊断中的应用，并描述混合OD病因中的MRI表现，以更好地了解其作为研究工具在该患者人群中的作用。
方法：PubMed的文献检索，Embase,科克伦,WebofScience,和Scopus完成了OD患者原始MRI数据的研究。排除了专门研究神经认知缺陷患者或研究OD的创伤性或先天性病因的患者的研究。
结果：来自1758篇候选文章，共纳入33项研究。四项研究回顾了特发性OD患者的MRI结构病理，其中372例患者中有17例（4.6%）有潜在的中心病因，3例（0.8％）患有嗅觉脑膜瘤或嗅觉神经母细胞瘤。14项研究（42.4％）报告了嗅球体积与嗅觉结果之间的显着相关性，6项研究(18.8%)报告灰质体积减少，特别是在眶额皮质，前扣带皮质,岛叶皮层,海马旁,和梨状皮质区域，混合型OD病因患者。功能性MRI研究报告嗅觉网络区域的大脑激活和功能连通性降低。
结论：MRI在特发性OD患者中发现颅内病理异常。在混合OD病因的患者中，嗅球和灰质体积减少是MRI上最常见的异常发现。需要进一步的研究，以更好地了解MRI的作用及其在获得性，特发性OD。
目的：本系统评价的目的是评估MRI在特发性OD诊断中的应用，并描述混合OD病因中的MRI表现，以更好地了解其作为研究工具在该患者人群中的作用。
方法：PubMed的文献检索，Embase,科克伦,WebofScience,和Scopus完成了OD患者原始MRI数据的研究。排除了专门研究神经认知缺陷患者或研究OD的创伤性或先天性病因的患者的研究。
结果：来自1758篇候选文章，共纳入33项研究。四项研究回顾了特发性OD患者的MRI结构病理，其中372例患者中有17例（4.6%）有潜在的中心病因，3例（0.8％）患有嗅觉脑膜瘤或嗅觉神经母细胞瘤。14项研究（42.4％）报告了嗅球体积与嗅觉结果之间的显着相关性，6项研究(18.8%)报告灰质体积减少，特别是在眶额皮质，前扣带皮质,岛叶皮层,海马旁,和梨状皮质区域，混合型OD病因患者。功能性MRI研究报告嗅觉网络区域的大脑激活和功能连通性降低。
结论：MRI在特发性OD患者中发现颅内病理异常。在混合OD病因的患者中，嗅球和灰质体积减少是MRI上最常见的异常发现。需要进一步的研究，以更好地了解MRI的作用及其在获得性，特发性OD。
