Brodie Abscess: MR imaging appearance in 10 patients

Abstract

The magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic "target" appearance with four layers: (a) a center with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR (short-inversion-time inversion recovery) images, (b) an inner ring isointense to muscle on T1-weighted images and with high signal intensity on T2-weighted and STIR images, (c) an outer ring hypointense on all images, and (d) a peripheral halo hypointense on T1-weighted images. In six of eight cases, a soft-tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR images. Only the peripheral halo was clearly identified in both cases.

The “Penumbra Sign” on Magnetic Resonance Images of Brodie’s Abscess: A Case Report and Literature Review

“…The 'penumbra sign' is a zone of transition with relatively high signal intensity on T1-weighted images between the abscess and reactive sclerosis. This zone of transition corresponds to the inner ring described by Marti-Bonmati et al [11]. Histologically, the 'penumbra sign' represents the vascularized granulation tissue wall surrounding the abscess cavity with a variable water content, which in turn determines the degree of hyperintensity on T1-weighted images [12].…”

“…Marti-Bonmati et al [11] first described the target appearance of the Brodie's abscess on MR imaging. They defined four distinct layers: (a) the centre (pus) which is reduced in intensity on T1-weighted and increased intensity on T2-weighted images, (b) the internal ring (abscess wall) which is isointense to muscle on T1-weighted and increased intensity on T2-weighted images, (c) the external ring (zone of reactive sclerosis) which is reduced in intensity on T1-weighted and T2-weighted images and (d) the peripheral halo (marrow edema) which is reduced in intensity on T1-weighted and increased on T2-weighted images.…”

Musculoskeletal Infection

“…A halo of T1-hypointense edema surrounds the hypointense rim [ 27 ]. The penumbra consists of a thin layer of granulation tissue that surrounds the abscess.…”

Diagnostic imaging of pediatric hematogenous osteomyelitis: lessons learned from a multi-modality approach

“…On plain films it usually presents as a welldefined osteolytic lesion, surrounded by reactive sclerosis [4][5][6][7][8]. On MR imaging, it typically shows a four-layer structure [21], with a ring of T1-shortening termed the "penumbra sign" [22]. It may contain purulent material, granulation tissue, or sequestrum, and may be associated with soft-tissue involvement after eroding the cortex.…”