Atypical infectious spondylitis with reduced bone marrow enhancement: “black vertebra sign”

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Abstract

Background: A few patients suspected of having infectious spondylitis exhibited a reduced enhancement pattern on postcontrast T1-weighted (T1W) magnetic resonance imaging (MRI). Purpose: To investigate the characteristics of infectious spondylitis patients who exhibited reduced vertebral enhancement. Material and Methods: From January 2010 to November 2017, 456 patients with findings suspicious for infectious spondylitis on 706 postcontrast T1W imaging were retrospectively evaluated. When an affected vertebra exhibited markedly reduced enhancement compared to normal bone marrow (BM), the vertebra was termed a “black vertebra.” MRI and computed tomography (CT) imaging findings within two-week intervals and the patients’ clinical characteristics were reviewed. Results: Ten patients (5 men, 5 women; mean age 66.4 years) whose MRI scans revealed the black vertebra sign were included. Among the 10 patients with black vertebrae, six patients exhibited signal voids in or around the affected vertebral bodies on T2-weighted (T2W) images. Eight patients showed air bubbles on CT images, suggestive of emphysematous infection. However, the typical image findings of infectious spondylitis were uncommon, namely, low BM signal intensity (SI) on T1W images (n=1) and intradiscal fluid-equivalent SI on T2W images (n=5) at an early stage. On follow-up MRI (average interval 7.2 weeks from initial MRI), available for five patients, marked progression of infection was evidenced by increased numbers of affected segments (n=3), low T1 SIs of the affected vertebrae (n=5), and increased contrast enhancement (n=3). Five patients underwent surgery to treat infections not controlled by antibiotics. Conclusion: A black vertebra sign on postcontrast T1W imaging seems to reflect an early emphysematous infection.

Original languageEnglish
Pages (from-to)1553-1561
Number of pages9
JournalActa Radiologica
Volume61
Issue number11
DOIs
StatePublished - 1 Nov 2020

Keywords

  • L Spine
  • contrast media
  • infection
  • magnetic resonance imaging

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