MR Evaluation of the Olfactory Bulb in Normals and Patients with Decreased Sense of Smell*

Yang, Kyung Hun; Kim, Man Ik; Moon, Yoo Bo; Kim, Ic Tae; Park, Young Min; Lim, Hyun Joon; Lee, Yul

Abstract

To evaluate changes in olfactory bulb size in patients with reduced or no sense of smell, 23 normals and 20 hyposmics or anosmics were examined with nasal endoscopy, olfactory testing and magnetic resonance imaging (MRI) of the olfactory bulb. Olfactory testing consisted of a threshold test by bounded three-alternative forced-choice modified ascending method of limits (CCCRC test) and the step method using threefold dilutions of 1-butanol and an olfactory identification test using 32 natural odors familiar to Koreans. The MR evaluation involved the estimation of olfactory bulb size by using a 13 cm diameter general purpose surface coil with 3 mm T1-weighted MR coronal sections without interval. The cut areas of the olfactory bulb in MR coronal sections were measured with a Hope Graph Planimeter (model No. 9-003) after fivefold enlargement. The olfactory bulb was observed in three cuts of MR imaging in all subjects. In the measured area of the olfactory bulb, the anterior portion of the olfactory bulb was significantly smaller than the middle and posterior areas in normals, but hyposmics or anosmics showed decreased olfactory bulb area, especially in height, when compared with normals. There was good correlation between olfactory bulb area and olfactory threshold as well as olfactory identification in normals and patients. MR imaging can be a useful tool for patients with hyposmia or anosmia.