PERIODONTOID CALCIUM PYROPHOSPHATE DIHYDRATE DEPOSITION DISEASE - PSEUDOGOUT MASS LESIONS OF THE CRANIOCERVICAL JUNCTION

Between 1984 and 1996, seven patients with symptomatic masses located posterior to the odontoid process and containing calcium pyrophosphate dihydrate crystals were evaluated by the senior author (A.H.M.). All patients presented with distal paresthesias and myelopathy and underwe nt transoral-transpharyngeal resection of the anterior arch of C-l, th e odontoid process, and the compressing mass. Histological examination revealed the characteristic changes of calcium pyrophosphate dihydrat e (CPPD) deposition disease, with nodular deposits of birefringent rho mboid crystals. On magnetic resonance imaging, the masses appeared pre dominantly isointense with neural tissue on T-1-weighted images and is o- to hyperintense on T-2-weighted images. On computerized tomography scans, small areas of calcifications within the masses were apparent i n all cases. All patients improved postoperatively, with six of seven patients requiring posterior fixation for instability as a second proc edure. Calcium pyrophosphate dihydrate deposition causing periodontoid mass lesions is a distinct clinical disease entity that probably is u nderdiagnosed. in the authors' opinion, the diagnosis can often be est ablished preoperatively by the distinctive neuroradiological appearanc e of the masses. Therefore, CPPD deposition disease should be consider ed in the differential diagnosis of masses of the craniocervical junct ion, because it is amenable to early surgical intervention. The consul ting neuropathologist should be made aware of this diagnostic possibil ity at the time of surgery.