Spinal gouty tophus presenting as an epidural mass lesion - A case report.

Introduction: Gout is a metabolic disease secondary to an increased body pool of urate with hyperuricemia. Gout typically affects the peripheral joints and rarely involves the intra-spinal area.

Case Presentation: A 43-year-old man, who had metabolic syndrome s/p bariatric surgery and gout suffered from severe left low back pain with radiation to the lateral side of his left thigh and anterior side of his left leg for more than 7 days. His L-spine MRI showed an abnormal posterior epidural space occupying lesion at L4-L5 level. For tissue diagnosis and neural structures decompression, he underwent surgical removal of the epidural mass lesion. The surgical specimen showed a picture of gout and he got a good recovery after operation.

Discussion: The differential diagnoses of an epidural mass includes synovial cysts, ligament cyst, cystic neuromas, tumors, hematomas and abscesses. Gout in the spinal canal is difficult to diagnosis before surgery because it is rare and its clinical presentation and radiologic findings mimic tumor, abscess, tuberculosis, and degenerative spinal diseases. Patients with spinal gout may present with axial pain and a variety of neurological symptoms.

Conclusion: Spinal gouty tophus should be considered in the different diagnoses of spinal epidural masses especially in patients with systemic gout. Surgery is needed for final diagnosis. If spinal gouty tophus is highly suspected during the surgery, the specimen should not be preserved with Formalin because birefringent crystals under polarized light is a unique feature for gouty tophus but they dissolve in Formalin.