Visualization of the olfactory nerve using constructive interference in steady state magnetic resonance imaging

The olfactory nerve (OlfN) is a small neural structure with inconsistent visualization on neuroimages. The aim of this study was to delineate the intracranial course of the OlfN using constructive interference in steady state magnetic resonance (MR) imaging. A total of 168 patients were enrolled in this study. Following initial examinations with conventional MR sequences, constructive interference in steady-state sequence (CISS) was performed in coronal and axial sections. On coronal sections, the OlfN was entirely visualized in 90 % of patients on the right and 92 % on the left, coursing along the olfactory sulcus. Complete visualization of the OlfN occurred in 100 % of patients on serial axial images. The OlfN was classified into four portions based on the topographical differences and surrounding structures. The olfactory fossa exhibited considerable variability at the midlevel of the olfactory bulb on coronal images. Characteristic appearance of the OlfN with respect to age range or gender was not observed. The OlfN follows a highly consistent course along the olfactory sulcus. Thin-sliced, CISS sequences are useful for consistent visualization of the OlfN.