Crowned Dens Syndrome Occurring after Endoscopic Submucosal Dissection for Early Gastric Cancer

Crowned dens syndrome (CDS) is a rare form of pseudogout which causes acute neck pain due to calcium pyrophosphate dehydrate deposition surrounding the odontoid process, commonly causing neck pain with rigidity. While invasive procedures such as surgery are known to present a risk of acute pseudogout, reports of occurrence after endoscopic procedures are scarce. We report the case of a 75-year-old man who presented with sudden neck pain after endoscopic submucosal dissection (ESD) for gastric cancer. He could nod but could not rotate his head. Computed tomography showed calcifications surrounding the odontoid process consistent with CDS. Prolonged dietary restrictions and proton pump inhibitor use following the ESD procedure may have caused hypomagnesemia, a precipitating factor for CDS. We prescribed colchicine 1 mg/day and symptoms resolved completely in 3 days. This is the first report of CDS after ESD. CDS should be included in the differential diagnosis of neck pain after endoscopic procedures.