Nasal thallium‐201 uptake in patients with parosmia with and without hyposmia after upper respiratory tract infection

• Published in: International forum of allergy & rhinology 2019-11, Vol.9 (11), p.1252-1256
• Main Authors: Shiga, Hideaki, Okuda, Koichi, Taki, Junichi, Watanabe, Naoto, Tonami, Hisao, Kinuya, Seigo, Miwa, Takaki
• Format: Article
• Language: English
• Subjects: Adult; Aged; Female; Humans; hyposmia; Intranasal administration; Magnetic Resonance Imaging; Male; Middle Aged; molecular imaging; nasal turbinate; nuclear medicine; Odor recognition; odor recognition threshold; Odor thresholds; olfaction; Olfaction Disorders - diagnosis; Olfactometers; Olfactometry - methods; Olfactory bulb; Olfactory Bulb - diagnostic imaging; Olfactory Bulb - pathology; Olfactory epithelium; Olfactory Nerve - diagnostic imaging; Olfactory Nerve - pathology; Original; Radionuclide Imaging; Respiratory tract diseases; Respiratory tract infection; Respiratory Tract Infections - diagnosis; sensory systems; single‐photon emission computed tomography; Smell; Thallium; Thallium Radioisotopes - metabolism
• ISSN: 2042-6976; 2042-6984
• DOI: 10.1002/alr.22395

Background In this study, we aimed to determine whether nasal thallium‐201 uptake of the olfactory cleft and olfactory bulb (OB) differs between patients with parosmia with and without hyposmia after upper respiratory tract infection (URTI). Methods Twenty patients with parosmia after URTI were enrolled in this study (15 women and 5 men, 28 to 76 years old). Nasally administered thallium‐201 migration to the OB, nasal thallium‐201 uptake ratio in the olfactory cleft, and OB volume were determined in 10 patients with normal T&T olfactometry (Daiichi Yakuhin Sangyo, Tokyo, Japan) odor recognition thresholds (≤2.0) who still complained of parosmia (parosmia group), and 10 patients with T&T odor recognition thresholds >2.0 (parosmia and hyposmia group). Results The nasal thallium‐201 uptake ratio in the olfactory cleft was significantly higher in the parosmia group than in the parosmia and hyposmia group (p = 0.0015). Thallium‐201 migration to the OB was not significantly different between the 2 groups (p = 0.31). The OB volume was significantly larger in the parosmia group than that in the parosmia and hyposmia group (p = 0.029); however, the mean OB volume in both the groups was lower than the normal threshold value in healthy individuals. Conclusion Our results signify the recovery of the olfactory epithelium; however, the olfactory neural projections to the OB and regeneration of OB were not complete in patients with parosmia with normal T&T recognition thresholds after URTI.