Olfactory Bulb Volume and Function Recovery in Eosinophilic Chronic Rhinosinusitis

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.