Presentation
Fevers and lower back pain
Patient Data
On early phase imaging, there is focal hyperemia in the midline lumbar spine on blood pool images.
On delayed phase planar imaging, there is moderatel-markedly increased tracer accumulation corresponding to the inferior endplate of L4 and the superior endplate of L5. SPECT/CT confirms moderate to intense uptake on either side of the L4/5 intervertebral junction, with corresponding destructive endplate changes on low dose CT.
Midline sagittal image of the lumbar spine demonstrates T1 hypointensity and gadolinium enhancement either side of the L4/5 intervertebral junction. There is also thickening and enhancement of the dura posterior to the L4 and L5 vertebral bodies. On the T2 sequence, there is hyperintensity in the L4/5 intervertebral disc and focally within the central inferior endplate of L4 (corresponding to the destructive change on low dose CT).
Case Discussion
This is a case of L4/5 discitis. Skeletal infection is typically characterized by hyperemia on early phase imaging and increased osteoblastic activity (tracer accumulation) on the delayed phase of the bone scan. In cases of discitis, there is increased osteoblastic activity in the endplates on either side of the affected disc.
It is important to assess for additional sites of osteoblastic activity elsewhere in the skeleton in cases of discitis, as infection may have seeded to other bones or joints (not present in this case).
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