Imaging Case of the Week 82

The following lumbar spine x-rays are from a 30 year old female patient who has been experiencing severe low back pain for the past few days. There is no history of trauma or fever. She is a type I diabetic. What can you glean from the x-rays?

Lumbar spine AP

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Lumbar spine lateral

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[peekaboo_link name=”Answer”]Answer[/peekaboo_link] [peekaboo_content name=”Answer”]

The lateral lumbar spine view shows focal irregularity/ erosion of inferior endplate of L2 and superior endplate of L3 anteriorly. There is also a moderate loss of disc height between L2 and L3. The AP view shows an incidental syndesmophyte at L2 level on the left side.

The patient was afebrile in the ED. She had a normal white cell count but high ESR and CRP on the initial blood tests in the emergency department.

She was admitted and underwent MRI and bone scan which led to the diagnosis of discitis with adjacent osteomyelitis of L2 and L3 vertebral bodies.

Lumbar spine lateral, discitis

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MRI sagittal T2 fat suppressed image

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MRI sagittal T1 fat suppressed post contrast

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bone scan

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Blood cultures were negative and an ECHO did not reveal any evidence of endocarditis (staph aureus commonest organism).

In general, plain x-rays are not useful in the diagnosis of discitis. However, an x-ray may show reduced disc height and erosion of the adjacent endplates.

CT is suboptimal to MRI in the diagnosis of discitis. CT may show vertebral endplate destruction/ erosion and an adjacent soft tissue mass or abscess. As in the case of plain imaging, CT findings may be positive only after several days.

MRI is the investigation of choice in the diagnosis of discitis. T1 weighted images show low signal and T2 fat suppressed images show high signal intensity at and adjacent to the endplates (Hypo on T1 and hyper on T2) and enhancement after IV gadolinium contrast (source: radiology textbooks).

Bone scan shows increased uptake at the site of infection. Bone scans are sensitive but not very specific (fractures, malignancy can have increased uptake). Bone scans are helpful to r/o multifocal infection.

Thanks to Dr. Stephen Chalk for the images.