Longer latency of sensory response to intravenous odor injection predicts olfactory neural disorder.

Seishi Kikuta ,Kensaku Mori,Kenji Kondo,Yu Matsumoto,Rumi Ueha,Kazunori Kataoka,Hironobu Nishijima,Hiromi Kojima,Makiko Toma-Hirano,Daiya Asaka,Kashio Akinori,Tatsuya Yamasoba,Nobuyoshi Otori,Koichi Tsunoda,Takashi Sakamoto,Takuhiro Yamaguchi,Kaori Kanaya,Tsuguhisa Nakayama,Ryoji Kagoya,Akihito Kuboki,Tempei Miyaji,Yuichiro Kikkawa

doi:10.1038/srep35361

Abstract

A near loss of smell may result from conductive and/or neural olfactory disorders. However, an olfactory test to selectively detect neural disorders has not been established. We investigated whether onset latency of sensory response to intravenous odor injection can detect neural disorders in humans and mice. We showed that longer preoperative onset latency of odor recognition to intravenous odor in patients with chronic rhinosinusitis predicted worse recovery of olfactory symptoms following sinus surgery. The onset latency of the olfactory sensory neuron (OSN) response to intravenous odor using synaptopHluorin signals from OSN axon terminals was delayed in mice with reduced numbers of OSNs (neural disorder) but not with increased mucus or blocked orthonasal pathways (conductive disorders). Moreover, the increase in onset latency correlated with the decrease in mature OSN numbers. Longer onset latency to intravenous odor injection is a useful biomarker for presence and severity of olfactory disorders with neural etiology.

Highlights

A near loss of smell may result from conductive and/or neural olfactory disorders
Onset latency of odor detection response using a pre-operative intravenous olfactory (IVO) test in patients having chronic rhinosinusitis with olfactory disorder correlates with post-operative olfactory symptoms
Chronic rhinosinusitis (CRS) patients with accompanying direct olfactory epithelium (OE) injury could be expected to show worse olfactory outcome following endoscopic sinus surgery (ESS) compared with CRS patients with accompanying conductive disorder only

Summary

Introduction

A near loss of smell may result from conductive and/or neural olfactory disorders. an olfactory test to selectively detect neural disorders has not been established. We investigated whether onset latency of sensory response to intravenous odor injection can detect neural disorders in humans and mice. The onset latency of the olfactory sensory neuron (OSN) response to intravenous odor using synaptopHluorin signals from OSN axon terminals was delayed in mice with reduced numbers of OSNs (neural disorder) but not with increased mucus or blocked orthonasal pathways (conductive disorders). Two parameters of the response in the IVO test, latency of odor recognition onset from the time of PST injection and duration between odor recognition onset and disappearance, are measured to determine olfactory loss (Fig. 1b); it is unclear whether these two parameters are differentially altered by specific pathological conditions, such as loss of OSNs or reduced odorant conduction

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Conclusion