Spondylodiscitis and Its Mimickers: A Pictorial Review

Abstract

Spondylodiscitis is an infection of the intervertebral disc, the adjacent vertebral body, and/or contiguous structures due to the introduction of infectious agent, usually by the hematogenous route. Imaging is crucial in assessing bacterial and tubercular spondylodiscitis, as well as their associated complications. Magnetic resonance imaging in particular can clearly depict osteo-structural changes in the vertebral body and the associated disc, as well as any soft-tissue complications, such as paravertebral abscess and/or epidural abscess, improving disease characterization and helping to recognize the agent involved. Nevertheless, other non-infectious diseases may mimic imaging appearances of spondylodiscitis and one should be aware of these conditions when interpreting MR images, which include Modic type I degenerative changes, ankylosing spondylitis, acute Schmorl's node, porotic fractures, and spinal neuropathy arthropathy. This pictorial review aims at describing imaging findings of bacterial and non-bacterial spondylodiscitis, complications, and those pathologies that mimic these infections.

Keywords: paravertebral abscess; spine infection; spondylodiscitis; tubercular infection; vertebral infection.

Scheme 1

Classification of spinal infections based on the location of the infection.

Figure 1

(A,B) MRI T2-weighted image on the sagittal plane shows marrow edema involving dorsal vertebra reaching up to the endplates (white arrows in A,B), with great enhancement on post contrast imaging (arrows in C) consistent with osteomyelitis. There is an increased amount of fluid signal in the intervertebral disc suggesting a discitis–osteomyelitis complex. (D) Post contrast imaging shows enhanced epidural soft tissue (yellow arrows D).

Figure 2

Tubercular spondylodiscitis. Axial (A) and coronal STIR (B), axial T1 with contrast (C,D), and sagittal CT (E) images demonstrate a severe morpho-structural alteration of the L2 vertebral body and partially of L1, with invasion of the paravertebral space with abscesses affecting the psoas muscles bilaterally (arrows).

Figure 3

E. Coli spondylodiscitis. In the sagittal T2 image (A) and T1 image (B), osteo-structural alterations with collapse and wedging of the vertebral bodies, accentuation of the physiological dorsal kyphosis, absence of the disc space, and partial vertebral fusion can be observed. In the sagittal (C) and axial (D) T1 image with contrast, bilateral paravertebral infectious collections are observed (arrows).

Figure 4

Sagittal fat-suppressed, T2-weighted imaging on the dorsal (A) and lumbar (B) spine shows multiple vertebral sites of infection (arrows) with signal changes in bone marrow and vertebral collapse (yellow arrow). Coronal (C) and axial (D) T2-weighted images show a wide collection in the paravertebral space (yellow arrows). A sagittal (E) CT scan and axial CT (F,G) show multiple fluid collection in the parasternal spaces (yellow arrows).

Figure 5

Type I Modic changes at L2–3 endplates showing a hyperintense signal (arrows) on an STIR image (A) and a T2-weighted image (B). The disc is characterized by degenerative changes, appearing reduced in height. There is no involvement of the surrounding paravertebral edema or psoas muscle.

Figure 6

Sagittal T2-weighted image (A) and STIR image (B) image show a well-defined, crescent nodule (arrow) located in the subchondral area of the L4 body.