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Crowned dens syndrome (axial calcium pyrophosphate deposition disease) — SCE Rheumatology MCQ

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ModerateMusculoskeletal ImagingCrowned dens syndrome (axial calcium pyrophosphate deposition disease)SCE Rheumatology

A 76-year-old woman presents with abrupt-onset severe upper cervical pain and marked restriction of neck rotation. Her temperature is 37.8°C and C-reactive protein is 126 mg/L. She has no focal neurological deficit. Blood cultures remain negative. She has previously experienced self-limiting attacks of acute knee synovitis, and knee radiographs show meniscal chondrocalcinosis. The current presentation raises suspicion of crowned dens syndrome due to axial calcium pyrophosphate deposition. Which imaging investigation is most appropriate to confirm this diagnosis?

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Correct answer: C — Conventional CT of C1–C2

The acute inflammatory neck syndrome, previous attacks compatible with acute CPP crystal arthritis and meniscal chondrocalcinosis together suggest crowned dens syndrome. Conventional CT focused on C1–C2 is the preferred imaging modality because it demonstrates the characteristic peri-odontoid calcification within the transverse and alar ligament region. Plain radiography may show peripheral chondrocalcinosis but is insensitive for peri-odontoid deposits because of overlapping anatomy. Ultrasound is recommended alongside radiography for peripheral CPPD, but the deep craniovertebral junction lacks a suitable acoustic window. Contrast-enhanced MRI can demonstrate adjacent inflammation and is important when discitis, epidural infection, cord compression or another soft-tissue process is suspected; however, it is less sensitive than CT for the defining calcification. Dual-energy CT is established principally for identifying monosodium urate deposition in gout. Its diagnostic role in CPPD is less established and it is not preferred over conventional CT for crowned dens syndrome. Thus, the axial location changes the imaging pathway from peripheral radiography or ultrasound to conventional CT.

Reference: 2023 EULAR recommendations on imaging in diagnosis and management of crystal-induced arthropathies in clinical practice (15 May 2024) — https://pubmed.ncbi.nlm.nih.gov/38320811/