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. 2018 Nov;8(11):1315-1322.
doi: 10.1002/alr.22144. Epub 2018 May 21.

Evaluation of idiopathic olfactory loss with chemosensory event-related potentials and magnetic resonance imaging

Jia Liu  1 , Jayant M Pinto  2 , Ling Yang  3 , Linyin Yao  1 , Xutao Miao  4 , Yongxiang Wei  1
Affiliations

Evaluation of idiopathic olfactory loss with chemosensory event-related potentials and magnetic resonance imaging

Jia Liu et al. Int Forum Allergy Rhinol. 2018 Nov.

Abstract
in English, Chinese

Background: Idiopathic olfactory loss (IOL) accounts for a sizable fraction of olfactory dysfunction, but very little is known about its etiology and electrophysiological changes in the olfactory pathway.

Methods: We analyzed the physiology of IOL using chemosensory event-related potentials (ERPs) (olfactory and trigeminal: oERP and tERP) and olfactory pathway magnetic resonance imaging (MRI) measured in adult patients with IOL and healthy controls. Subjective olfactory function was measured by Toyota and Takagi (T&T) olfactometry and Sniffin' Sticks (SS).

Results: Olfactory function was worse in patients with IOL compared to controls (T&T, p < 0.001; SS, p < 0.001). oERPs could be evoked in 17 IOL patients. Signals in these patients showed lower amplitude in the N1 and P2 waves than controls (p < 0.05 for both), but there were no difference in latency between the 2 groups (p > 0.05). tERP were detected in all patients and controls; there were no differences in latency and nor amplitude between the 2 groups (p > 0.05). The olfactory bulb (OB) volume was significantly smaller in the IOL group than controls (p < 0.001), but there was no difference in the olfactory sulcus depth between groups (p > 0.05). Better olfactory function was associated with increasing magnitude of N1 amplitude in oERPs (p < 0.05) and increasing OB volume (p < 0.05).

Conclusion: IOL patients show neurophysiologic deficits and some anatomic differences compared to healthy controls.

背景: 尽管特发性嗅觉下降 (IOL) 在嗅觉障碍人群中所占比例相当可观, 但是相关病因学机制及嗅觉通路相关电生理变化并不十分清楚。

方法: 通过对比成人IOL及健康人群的化学感受事件相关电位 (ERPs) 及嗅觉通路核磁共振成像 (MRI) 的差异, 我们分析IOL的生理机制。同时采用Toyota和Takagi (T&T) 嗅觉测定法及Sniffin'Sticks嗅觉心理物理测试 (SS) 对患者主观嗅功能进行评定。

结果: 与对照组相比, IOL患者嗅功能更差(T&T, p < 0.001; SS, p < 0.001)。17例IOL患者诱发出oERPs (嗅神经化学感受事件相关电位) , 这些患者N1、P2波振幅与对照组相比明显降低(p 均 < 0.05), 但两组间潜伏期无明显差异(p > 0.05)。所有患者及健康人群均能检测出tERP (三叉神经感受事件相关电位) ;两组间潜伏期、振幅变化无统计学差异(p > 0.05)。IOL组嗅球 (OB) 体积明显小于对照组(p < 0.001), 但组间嗅裂深度无统计学差异(p >0.05)。嗅觉功能与oERPs中N1振幅幅度、OB体积呈正相关(p 均< 0.05)。

结论: 与健康对照组相比, IOL患者呈现出部分神经生理学缺陷及解剖学异常。

Keywords: MRI; chemosensory event-related potentials; clinical features; idiopathic olfactory loss; olfactory function.

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Figures

Figure 1
Figure 1
Total amplitude of N1 wave in oERPs (Cz site) from IOL patients and controls. *p < 0.05 (independent sample t test). IOL = idiopathic olfactory loss; oERP = olfactory event‐related potential.
Figure 2
Figure 2
Total amplitude of P2 wave in oERPs (Cz site) from IOL patients and controls. *p < 0.05 (independent sample t test). IOL = idiopathic olfactory loss; oERP = olfactory event‐related potential.
Figure 3
Figure 3
(A) Grand average for oERPs in IOL patients (blue line) and controls (red line) recording in position Cz. (B) oERPs in position Cz from a 43‐year‐old IOL patient (blue line) and an age‐matched healthy subject (red line). IOL = idiopathic olfactory loss; oERP = olfactory event‐related potential.
Figure 4
Figure 4
MRI of olfactory pathway: bilateral OB volume decreased in IOL patients (left); the structure of OB and OS in healthy subjects (right). IOL = idiopathic olfactory loss; OB = olfactory bulb; OS = olfactory sulcus.
See this image and copyright information in PMC

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