MRI to detect and localize the area postrema in multiple sclerosis: The role of 3D-DIR and 3D-FLAIR

Background And Purpose Area postrema (AP) is a highly vascularized paired 2 mm-long anatomical structure, localized on the dorsal inferior surface of the medulla oblongata, at the caudal end of the fourth-ventricle. AP is principally affected in AP syndrome, which is commonly associated with autoimmune inflammatory diseases, including essentially neuromyelitis optica spectrum disorder (NMOSD). The aim of this study is to assess the best cerebral MRI sequences and planes for AP detection in order to assist or aid in the diagnosis of difficult NMOSD cases. Methods 3DT1, 2DT2, 3D-fluid-attenuated inversion recovery (3DFLAIR), and 3D-double inversion recuperation (3DDIR), routinely used in inflammatory diseases, were analyzed and scored based on quality (0-2), and ability to detect AP in each plane (0 = no detection, 1 = probable detection, 2 = obvious detection). Based on image availability, subjects were divided into three groups: Group-1, including 100 randomly selected subjects with 3DT1 and 3DFLAIR, Group-2, including 30 multiple sclerosis (MS) patients from the "Observatoire Francais de la Sclerose En Plaques" (OFSEP) with 3DT1, 3DFLAIR, and 3DDIR, and Group-3, including 164 OFSEP MS patients with 3DFLAIR and 2DT2. Results AP was undetectable on 3DT1 and 2DT2. AP was detected in 87% of 3DFLAIR in Group-1, 90% in Group-2, and 90% in Group-3. AP was also detected in 100% of 3DDIR images in the axial plane. Conclusions As evidenced, AP was easily assessed on 3DDIR and 3DFLAIR emphasizing the importance of adding these sequences to NMOSD MRI-protocols. Moreover, the most effective imaging plane in identifying AP was the axial plane.