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Diffusion-weighted imaging of spinal and paraspinal infections: characteristic findings, differential diagnoses and imaging pitfalls 2012

General Spine

Toshio, Moritani, MD, PhD
Aaron, Berg, MD, Non ASSR Member
John, Kim, MD, Non ASSR Member

Poster

Purpose

To demonstrate diffusion-weighted imaging (DWI) of spinal and paraspinal infection, including spinal and paraspinal infections, which included abscesses, pus collections, cellulitis and granuloma formations, in the subarachnoid, subdural and epidural spaces, and paraspinal soft tissues and iliopsoas muscle. These lesions were often associated with discitis, osteomyelitis or facet joint arthritis. We illustrate their mimics and imaging pitfalls.

Methods & Materials

We reviewed DWI findings in 258 patients with spinal and paraspinal infections, which included abscesses, pus collections, cellulitis and granuloma formations, in the subarachnoid, subdural and epidural spaces, and paraspinal soft tissues and iliopsoas muscle. These lesions were often associated with discitis, osteomyelitis or facet joint arthritis. Underlying diseases and predisposing factors comprised of sepsis (endocardirtis, IV drug user, urinary tract infection), spine surgery, infected aortic aneurysm graft, spinal or paraspinal tumor, trauma, diabetes, liver cirrhosis, renal/liver transplant, and epidural steroid injection. The causes were various types of infections including common bacterial infections, tuberculosis, brucellosis, and fungal infections. The diagnosis was made based on clinical, pathological, laboratory and imaging findings. Spin-echo type echo-planar DWI with parallel imaging and the ADC maps (b=0, 1000 sec/mm2) were used.

Results

DWI showed hyperintensity in abscesses and pus formations in subarachnoid, subdural, and epidural disc spaces, and psoas and paraspinal regions. Lower ADC values were observed in these lesions in comparison to the ADC values of the spinal cord, muscle, postoperative fluid collections (seromas, pseudomeningocele, hematoma) and CSF. DWI was useful for the diagnosis, treatment plan, decision making of surgical drainage and site selection for the biopsy in patients with spinal and paraspinal infections. We also demonstrate spinal and paraspinal infection mimics and differential diagnosis on DWI including subarachnoid hemorrhage, subdural and epidural and hematomas, CSF leak, postoperative fluid collections and hematomas, epidermoids, necrotic spinal and paraspinal tumors, and extruded and sequestrated disc herniations. We also discuss the limitations on DWI mainly due to susceptibility artifacts (surgical device etc.) and the calculation of ADC values in the tissue containing bone and fat.

Conclusion

DWI is useful for the detection of spinal, paraspinal and psoas abscesses and pus formations. We illustrate their mimics, and discuss the imaging pitfalls and limitations on DWI and ADC maps.

References/Financial Disclosures

Pui MH, Mitha A, Rae WI, Corr P. Diffusion-weighted magnetic resonance imaging of spinal infection and malignancy. J Neuroimaging. 2005;15:164-170 Eastwood JD, Vollmer RT, Provenzale JM. Diffusion-weighted imaging in a patient with vertebral and epidural abscesses. AJNR Am J Neuroradiol. 2002;23:496-498

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