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

Abstract

This report presents the “penumbra sign” of a Brodie’s abscess in a 69-year-old male patient. The lesion was located in the proximal metaphysis of the left tibia. Histopathology confirmed the diagnosis of subacute osteomyelitis. The penumbra sign on magnetic resonance (MR) images is a helpful sign for the diagnosis of Brodie’s abscess.

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

“…The 'penumbra sign' is not pathognomonic but is an important characteristic MR imaging feature with reasonably high specificity, reported as greater than 90% [5] in the diagnosis of subacute osteomyelitis of Brodie. However, 'penumbra sign' has also been observed in other bone conditions such as Langerhans cell histiocytosis [13], chondrosarcoma [12] and lymphoma [14].…”

“…The clinical presentation of Brodie's osteomyelitis is elusive and so the diagnosis is often delayed [3,5]. Pain is the most common presenting symptom in most patients followed by minimal loss of function or limping [3].…”

“…Sometimes the clinical and radiographic features may be ambiguous making differentiation of Brodie's abscess from other benign and malignant bone tumors difficult [3]. The 'penumbra sign', which is a high signal intensity thin layer of granulation tissue that lines the abscess cavity on unenhanced T1-weighted magnetic resonance (MR) images, has been found to be helpful in the diagnosis of Brodie's osteomyelitis [4,5]. This report highlights the importance of a 'penumbra sign' in differentiating between Brodie's abscess and other bone tumors or lesions on MR imaging.…”

Der Brodie-Abszess – eine interdisziplinäre Herausforderung

“…eine subakute Osteomyelitis (9). Afshar weist darauf hin, dass von verschiedenen Autoren für dieses Bild im MRT als Zeichen einer subakuten Osteomyelitis eine Sensitivität von 75 % und eine Spezifität von über 90 % angegeben wird (11). Somit sind jedoch auch durch diesen MRT-Befund andere gutartige und bösartige Knochenläsionen nicht auszuschließen.…”

Localized Langerhans cell histiocytosis masquerading as Brodie’s abscess in a 2-year-old child: a case report

“…Brodie's abscess, on the other hand, is a common type of subacute osteomyelitis. A characteristic feature of Brodie's abscess is the penumbra sign, seen as a rim lining of an abscess cavity with higher signal intensity than that of the main abscess on T1-weighted images (Afshar and Mohammadi, 2011[ 1 ]). However, a mass with peripheral rim enhancement and penumbra sign are usually considered features of Brodie's abscess (Bohndorf, 2001[ 3 ]).…”