Background/Purpose: Crowned Dens (CD) is the radiological finding of calcium pyrophosphate dihydrate (CPPD) crystal deposition in the cruciform and alar ligaments giving the appearance of a crown surrounding the dens. When these imaging findings are associated with recurrent shoulder girdle stiffness and pain, fever and/or elevation of acute phase reactants, it is Crowned Dens Syndrome (CDS). Clinical presentation is similar to Polymyalgia Rheumatica (PMR), however CDS clinical course and management are different. We hypothesize that CDS is misdiagnosed as PMR in some cases. This study was performed as a quality improvement project to promote early recognition of CDS.

Methods: This study was based on a retrospective analysis of electronic medical records of 501 charts at the Syracuse VA Medical Center between 08/2018 and 08/2023. Available CT Head and/or Neck were reviewed with attending radiologists looking for evidence of calcification around the dens (Figure 1). Data was collected by chart review including age, gender, history of peripheral CPPD, prior diagnosis of PMR, cervical/shoulder pain or stiffness, hip girdle pain, ESR and CRP. Additionally, PTH, calcium, vitamin D, phosphorus, magnesium, ferritin, alkaline phosphatase values were collected to rule out secondary causes of CPPD. We also collected treatment modality with NSAIDs, glucocorticoids or DMARDs. Additionally, we analyzed a total 186 patients with peripheral CPPD without history of neck pain. Statistical analysis was performed calculating Fisher’s Exact Test p-value.

Results: 315 total charts of patients diagnosed with Polymyalgia Rheumatica were reviewed. 195 had accessible charts out of which 69 had available CT Head and/or Neck done for other indications. 19 of the 69 patients had imaging and clinical findings consistent with Crowned Dens Syndrome (27.54%). Median age was 78 and 18/19 were males. All 19 patients had symptomatic peripheral CPPD at different intervals. 17/19 had elevated ESR (89.47%) and 15/19 had elevated CRP (78.94%). Only one patient had fever on presentation and 2/19 had associated hypothyroidism. All patients were treated with variable doses of glucocorticoids for at least 6 months. On the other hand, out of all patients with peripheral CPPD without neck pain, CT Scan Head and/or Neck were available on 81 patients. 65/81 had evidence of crowned dens (80.2%) without symptoms of neck pain or stiffness.

Conclusion: Our study indicates that CPPD deposition frequently involves the dens on patients with established peripheral CPPD in approximately 84% of the cases (p-value < 0.0001; table 1). Our data suggests that a sizable percentage (approximately 22%) of these patients have symptomatic Crowned Dens Syndrome that was misdiagnosed as PMR. Clinicians should recognize this important differential diagnosis to avoid unnecessary tests and treatment, especially on patients with established CPPD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/exploring-the-prevalence-of-crowned-dens-syndrome-in-a-polymyalgia-rheumatica-veterans-affairs-patient-cohort/