Infections of the Spine: A Review of Clinical and Imaging Findings

Vikram K. Sundaram, MD; Amish Doshi, MD

Disclosures

Appl Radiol. 2016;45(8):10-20. 

In This Article

Fungal Spondylodiscitis

Clinical Findings

Similar to tuberculous spondylodiscitis, fungal spondylodiscitis tends to have an indolent course in contrast to pyogenic spondylodiscitis. Immunocompromised patients carry a higher risk of spinal column infections from fungi such as Aspergillus, Candida, and Mucor species. Other fungi have regional predilections, and can affect immunocompetent patients with the proper exposure history. Examples of such fungi include Blastomyces, Coccidioides, and Histoplasma. If suggestion of indolent course and suspicion for fungal exposure and/or susceptibility can be matched to an imaging pattern for fungal infection, it is worthwhile for the clinician to pursue confirmation with laboratory data and/or direct sampling to guide treatment.

Imaging Findings

Plain Radiographs and CT. Similar to tuberculosis, fungal spondylodiscitis tends to involve the anterior vertebral body, has a predilection for paraspinal encroachment, and tends to spare the intervertebral disc due to a lack of proteolytic enzymes. Some patterns can help to distinguish amongst the various fungal species. For instance, Blastomyces can cause vertebral body collapse and the gibbus deformity like tuberculosis, and can be distinguished from tuberculosis by the presence of lesions in adjacent ribs. Coccidioides tends to also involve the posterior elements and more often than not demonstrates paravertebral spread. Other interesting features are better appreciated on MRI.

MRI. In general, fungal infections tend to show more subtle changes on MRI when compared to pyogenic and tuberculous spondylodiscitis. Low T1 and high T2 signals are faint, and contrast enhancement is scant due to relatively mild inflammatory changes in fungal infections. As the disease becomes more chronic, patterns emerge in certain species. Both Aspergillus and Blastomyces infections tend to involve multiple and sometimes non-contiguous vertebral bodies, can cause enhancement of the longitudinal ligaments, and, in severe cases, can cause significant vertebral body destructive changes. Additionally, Aspergillus can cause intervertebral disc protrusion in some instances. In Candida infections, an important finding is the presence of high T2 signal microabscesses that can appear similar to a granuloma of the vertebral body. Although rare, Candida can also produce intramedullary abscesses that show contrast enhancement (Figure 10).

Figure 10.

Axial CT bone window (A) and axial CT postcontrast (B) as well as sagittal T1 postcontrast sequences (C) of the lumbar spine of a 22-yr-old man with suspected fungal spondylodiscitis. Findings include right psoas abscess extending from L1/L2 to L2/L3 (B, solid arrow), and left psoas abscess extending from T12/L1 to L4/L5 as well as to left quadratus lumborum muscle (B, dotted arrow). There is a focus of enhancement within the L2 vertebral body on sagittal MRI sequences (C, arrow).

Follow-up Imaging

Similar to tuberculous spondylodiscitis, fungal spondylodiscitis tends to have a more chronic time course, and so follow-up imaging with CT and MRI tends to focus on documenting patterns of bony destruction, resolution of vertebral infectious foci, and resolution of paraspinal extension.

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