Evaluation of olfactory bulb volume in patients with diabetic olfactopathy and comparison with healthy individuals

Objective: Diabetic olfactopathy is defined as olfactory dysfunction in patients with diabetic neuropathy. In this study, we evaluated the olfactory bulb volume (OBV) using magnetic resonance imaging in patients with diabetic olfactopathy and compared the results with those of healthy individuals. Methods: This study included 12 patients who were diagnosed with type 2 diabetes mellitus (T2DM) and were found to have diabetic olfactopathy using the Connecticut Chemosensory Clinical Research Center (CCCRC) olfactory test (Group 1); their OBV was evaluated using MRI. For comparison, 13 healthy individuals of a similar age, without any medical problems, were included as a control group (Group 2); their OBV and olfactory functions were also evaluated. Results: Total CCCRC scores were 4.27 +/- 0.67 in Group 1 and 6.42 +/- 0.31 in Group 2; these scores significantly differed between the groups. The mean CCCRC scores in Groups 1 and 2 were moderately hyposmic and normosmic, respectively. The mean OBV values were 65.04 +/- 6.97 mm(3) and 76.46 +/- 11.36 mm(3) in Groups 1 and 2, respectively. Group 1 had significantly lower OBV values and CCCRC scores, compared with Group 2 (p < 0.01 for both groups). Conclusion: The OBV was lower in patients with T2DM who developed diabetic olfactopathy than that in healthy individuals; the olfactory bulb was adversely affected by diabetes mellitus. This is the first study to demonstrate that the olfactory bulb is adversely affected by the presence of diabetic olfactopathy.