Olfactory Bulb Volume and Function Recovery in Eosinophilic Chronic Rhinosinusitis

To evaluate perioperative changes in olfactory bulb volume (OBV) and olfactory function in patients with eosinophilic chronic rhinosinusitis (ECRS) using 3T magnetic resonance imaging (MRI) with fast imaging employing steady-state acquisition (FIESTA) sequence and to assess their associations.

This single-center, retrospective observational study included 32 patients with ECRS who underwent functional endoscopic sinus surgery. Olfactory function was assessed pre- and postoperatively using the Alinamin test, T&T olfactometer, Open Essence (OE), Odor Stick Identification Test for Japanese (OSIT-J), Visual Analog Scale (VAS), and Self-Assessment Olfactory Questionnaire (SAOQ). OBV was manually measured from FIESTA images. Logistic regression was used to identify preoperative predictors of OBV change.

Postoperative OE, OSIT-J, VAS, and SAOQ scores improved significantly. Mean OBV increased by 10.3% postoperatively, although not statistically significant (p = 0.095). OBV change correlated with improvements in olfactory identification (OE: r = 0.404, p = 0.022; OSIT-J: r = 0.402, p = 0.022), which should be interpreted as exploratory. Multivariate analysis revealed that longer odor duration on the Alinamin test (≥ 50 s) and higher SAOQ scores predicted smaller OBV increases.

OBV measurement using 3T MRI with FIESTA may provide a structural correlate of olfactory changes in ECRS. The observed correlation between OBV changes and olfactory identification suggests a potential relationship with postoperative functional recovery.