Spondylodiscitis Case Report

(Collaboration of Enrique Hiplan MD.)

 

Women 18 years old, without previous diseases. Presents with spontaneous and non-traumatic lumbar pain . Initial evaluation with lumbar x-ray, found a possible L3 and L5 vertebral fracture. Computed tomography and bone scan were negatives. MRI, showed abnormal bone marrow at the right lateral aspect of L2, L3 and L4, suggeting to rule out lymphoproliferative syndrome

Bone marrow biopsy was negative for neoplasic cells or infectious disease. After two months, lumbar pain augmented, with scarce response to analgesic treatment. At this moment, PET-CT 18F-FDG was requested.

PET-CT 18F-FDG showed  inflammatory and  hypermetabolic lesion in the pre-vertebral soft tissues, with invasion of psoas muscle, inter-vertebral L4-L5 disc and bone involvement of the inferior vertebral platform of L4 and superior of L5. SUV max value was 18.7 (arrows). See figures.

A second bone marrow biopsy was performed, resulting positive for infectious disease. After five weeks of antibiotics treatment the patient.

Spondylodiscitis is a condition that includes spondylitis, discitis, and vertebral osteomyelitis and accounts for 2% to 4% of all bone infections.

Early diagnosis is difficult, and it may take up to 4-8 weeks from the onset of symptoms (fever and back pain), and the development of radiographic abnormalities (1).

MRI is currently the imaging modality of choice, with a sensitivity of 96% and a specificity of 92%.  FDG PET has an excellent performance to exclude spondylodiscitis (1).

Previous studies have indicated that MRI is the most accurate modality for the early detection of spondylodiscitis. 18F-FDG PET/CT has a higher spatial resolution and can differentiate between bone and soft tissue infection, and allows imaging in the presence of metal implants (2).

A meta-analysis of 12 studies provided diagnostic data on 18F-FDG PET/CT in spondylodiscitis and confirmed its suitability for exclusion of infection. Our results with 18F-FDG PET/CT in the diagnosis of infection of the spine, with a sensitivity of 83 %, a specificity of 88%and an outstanding PPV of 94 % (2).

FDG PET/CT may be used as a tool to assess the response to antibiotic therapy very early in patients affected by haematogenous spondylodiscitis, especially in those with a nondiagnostic CRP test at diagnosis.

 A decrease in SUVmax (measured before therapy and 2 to 4 weeks after the start of therapy) of at least 34 % is strongly predictive of a complete response, providing a sensitivity and specificity of 82 % (3).

 

References:

(1) Michael L. Prodromou et al. FDG PET Is a Robust Tool for the Diagnosis of Spondylodiscitis. Clin Nucl Med 2014;39: 330Y335.

(2) David Fuster et al. Prospective comparison of whole-body 18F-FDG PET/CT and MRI of the spine in the diagnosis of haematogenous spondylodiscitis. Eur J Nucl Med Mol Imaging (2015) 42:264–271.

(3) Cristina Nanni et al. FDG PET/CT is useful for the interim evaluation of response to therapy in patients affected by haematogenous spondylodiscitis. Eur J Nucl Med Mol Imaging (2012) 39:1538–1544.

 

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