Not Always Crystal Clear: Pseudogout as a Cause of Lumbar Radicular Pain-A Case Report

BACKGROUND: Calcium pyrophosphate crystal deposition (CPPD) also known as "pseudogout" is a lesser-known cause of radicular pain that can occur in the spine after surgical intervention. Crystals may deposit extradurally in the ligamentum flavum, facet joints, and intervertebral discs causing symptoms ranging from mild-to-intractable radicular pain or cauda equina syndrome. CASE REPORT: A 60-year-old man with a history of multiple lumbar surgeries and recent right L2-L3 hemilaminectomy/facetectomy presented with severe, radicular pain. Physical exam demonstrated decreased left L5 dermatome sensation. Postop imaging confirmed worsening foraminal encroachment at L5-S1 compared to preop imaging. The patient failed steroid taper, neuropathic agents, nonsteroidal anti-inflammatory drugs, physical therapy, and 3 L5-S1 epidural steroid injections. He ultimately underwent L5-S1 microdiscectomy where numerous crystalline deposits were identified and sent for pathology, revealing CPPD with foamy histiocytes. CONCLUSIONS: Clinicians should consider CPPD in at-risk patients with radicular pain following surgery to expedite appropriate workup and rheumatologic management.