The Gouty Spine

 Gout is classically a disease of the appendicular skeleton with characteristic radiologic features (sclerotic, well-marginated erosions with overhanging edges), diagnostic joint aspiration findings (needle-shaped negatively birefringent monosodium urate crystals), and typical serum abnormalities (hyperuricemia).  Gout also tends to strike characteristic locations, especially the well-recognized site at the first metatarsophalangeal joint ("podagra")

But despite its characteristic findings and locations, the relatively high prevalence of gout leads to a number of atypical presentations, including gout located in the discs and facet joints of the spine.  The majority of spinal involvement in gout occurs in patients who already carry a known diagnosis, so it's not too challenging to put it on the differential for acute back pain...
... what can be challenging is using imaging to determine whether findings in the spine in a patient with a history of gout are related to an unusual site of gouty attack, or whether they are related to a concurrent, much more common process (e.g. osteomyelitis or epidural abscess).

Radiographic and CT imaging can show vertebral endplate erosion, disc space narrowing, and a soft tissue mass (tophus), but these findings lack specificity, and, although gouty involvement of the spine is rare, tophi have been mistaken for tumor or abscess in the past.  The axial CT image below comes from a 27Y M with a 6 month history of low back pain and a four year history of hyperuricemia, and demonstrates hyperdense periarticular deposits with diffuse stippled calcifications and juxta-articular bony erosions around the facet joints.

 

MRI adds more specificity to the findings, and adds information related to potential spinal cord or nerve root compression, but it still lacks specificity... especially since a tophus can show quite variable presentations.  The sagittal T1, T2, and postcontrast T1 images below come from the same 27Y M patient as above:

T2WI: Heterogeneous signal within the tophus

T1WI: Heterogeneous low signal in the tophus

Postcontrast T1WI: Variable enhancement within the tophus

Given the variability in MRI presentation, this modality seems most useful to decide against other masses with more characteristic presentations, and to assess neurologic impingement.

A new and elegant method of diagnosis of spinal gout involves the use of dual-energy CT scanning.  Since calcium and urate demonstrate different attenuation characteristics at different kVp values, urate deposition can be isolated and color coded as in the example below.

  

 This image on the right is the color-coded dual energy CT image showing urate crystal deposition in the facet joints (green) of an 82Y man with worsening back pain.  Not surprisingly, he had not been receiving relief from multiple steroid injections for his advanced degenerative disease.

Of note, reports of gouty involvement of the spine range from the cervical spine to the lumbar spine and sacroiliac joints, and there appears to be no preferential spinal location.


1. Staub-Schmidt T, Chaouat A, et al. "Spinal Involvement in Gout" Arthritis & Rheumatism 38:1, 1529-0131
2. King JC, Nicholas C. "Gouty arthropathy of the lumbar spine: a case report and review of the
literature" Spine (Oct 1997) 1;22(19):2309-12.
3. Hsu CY, Shih TT. "Tophaceous gout of the spine: MR imaging features" Clin Radiol. 2002 Oct;57(10):919-25.
4. Madhura D, Peterson J,et al. "Clinical Utility of Dual-Energy CT for Evaluation of Tophaceous Gout" Radiographics September-October 2011 31:1365-1375