Background/Purpose:   Crowned Dens Syndrome (CDS), a variation of Calcium Pyrophosphate Deposition Disease (CPPD), is a radiologic-clinical entity defined by the association of radiological calcifications around the odontoid process and periodic cervico-occipital pain. The true incidence and prevalence of CDS in the general population or in those with CPPD remain unknown. Here, we discuss 34 patients as one of the largest reported series.

Methods: This is a retrospective chart and radiology registry imaging study review from a single tertiary medical center from 11/1/2005-10/31/2015. 191 patients with a diagnosis of CPPD and/or CDS were identified. Terms used in the search included pseudogout, CPPD, CDS, chondocalcinosis and calcification. 57 patients had at least one c-spine CT performed for a variety of indications.  The CTs were analyzed by a musculoskeletal radiologist for the presence of periodontoid calcifications.

Results:   Of the 191 patients with CPPD, 57 had c-spine CTs obtained; 34 of whom (34/57, 59.64%) had periodontoid calcifications. Only 12/34 patients were formally diagnosed with CDS by rheumatologists.  The others (22/34) were either not seen by a rheumatologist or were not diagnosed with CDS if seen by other specialists. The median age of diagnosis was 78.5 years, with majority (73.52 %) over 70 y/o and 24/34 (70.58%) were female. 17/34 patients (50%) were symptomatic; defined as presence of acute to sub-acute neck pain within 6 weeks of performing the c-spine CT. The majority of the patients (82.35%, 28/34) had additional sites of chondrocalcinosis on joint radiographs; 8 patients (28.57%) had 3 or more sites of chondrocalcinosis in typical CPPD locations. Six patients did not have any joint radiographs. 16/34 patients (47.05%) who had CDS and chondrocalcinosis elsewhere, also carried metabolic diseases, including: hyperparathyroidism (2), hypothyroidism (10), hypomagnesemia (2) and hypophosphatemia (2). None of the patients had a documented history of hemochromatosis or evidence of iron overload based on laboratory tests.

Conclusion: Crowned Dens Syndrome is an under-recognized entity, which should be considered in elderly patients with neck pain in the setting of CPPD. Our data demonstrates a high percentage (about 60%) of patients with CPPD who had c-spine CT findings consistent with CDS. This underscores the importance of performing c-spine CTs when evaluating patients with neck pain and CPPD or chondrocalcinosis in other joints, as radiographs and MRI may not be diagnostic of CDS.