PMC6159294_01
Sagittal pre-contrast T1 (a), T2 (b), and post-contrast T1 (c) images show an intradural extramedullary serpiginous tubular lesion (solid arrows) extending from T12 to L3, with intermediate signal on T1 weighted images, peripheral hypointensity and central hyperintensity on T2 weighted images (the "doughnut" sign, dotted arrow) and avid homogeneous enhancement. The "doughnut" sign is also present on multiple axial T2 slices (d and e, dotted arrows). Avid enhancement within the lesion is also visualized on axial T1 post-contrast images (f, solid arrow).
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f1
T1 sequences most likely relates to MR artefacts from slow venous flow. The peripheral hypointensity and central hyperintensity on T2 weighted imaging, which we have been referred to as the "doughnut" sign (Figure 1), may also be the result of a combination of flow void peripherally and slow flow centrally. This hypothesis is further supported by the pattern of enhancement on the blood pool phase MRA with central relatively reduced enhancement compared to the periphery.