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

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

A 78-year-old woman with previous acute calcium pyrophosphate crystal arthritis and radiographic chondrocalcinosis of the knees and wrists presents with 36 hours of severe upper cervical and occipital pain. She is unable to rotate her neck because this markedly exacerbates the pain. Her temperature is 37.8°C, neutrophil count is 12.1 × 10^9/L and CRP is 96 mg/L. She has no visual disturbance, jaw claudication, scalp tenderness, limb-girdle symptoms, photophobia, altered cognition or focal neurological deficit. There is no recent trauma or infective focus. Which imaging investigation is most appropriate to establish the suspected rheumatological diagnosis?

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Correct answer: A — Unenhanced CT of the craniocervical junction with thin sections through C1–C2

The presentation is characteristic of crowned dens syndrome, an axial manifestation of calcium pyrophosphate deposition disease. The discriminating features are advanced age, established peripheral CPPD, abrupt inflammatory upper cervical pain, profound restriction of rotation and raised inflammatory markers without clinical features of giant cell arteritis, meningitis or neurological compression. Unenhanced CT focused on C1–C2 is the preferred imaging modality because it demonstrates linear or crown-like calcification within the transverse and other peri-odontoid ligaments. MRI may show surrounding inflammation but is less sensitive for calcification; it becomes preferable when spinal infection, a soft-tissue mass or neurological compression is suspected. Plain radiographs may identify cervical calcification but are substantially less sensitive than targeted CT. Temporal and axillary artery ultrasound would be appropriate for suspected giant cell arteritis, but the relevant cranial and polymyalgic features are absent. CT angiography assesses vascular pathology such as cervical artery dissection rather than peri-odontoid crystal deposition and would be indicated if there were trauma, focal neurological signs or an appropriate vascular pain syndrome.

Reference: 2023 EULAR recommendations on imaging in diagnosis and management of crystal-induced arthropathies in clinical practice (6 February 2024) — https://ard.bmj.com/content/83/6/752 Clinical features and diagnostic challenges in crowned dens syndrome: a systematic review and meta-analysis (2025) — https://pubmed.ncbi.nlm.nih.gov/40278908/