Deposition of calcium pyrophosphate dihydrate crystals in the ligamentum flavum: evaluation with MR imaging and CT.

Four patients had spinal canal stenosis associated with deposition of calcium pyrophosphate dihydrate within the ligamentum flavum. Radiologic evaluation was performed with magnetic resonance imaging or computed tomography, and surgery was performed on all four patients. Pathologic examination of the surgical specimens demonstrated deposits of calcium pyrophosphate crystals within the ligamentum flavum. Focal enlargement of the ligamentum flavum was present in the cervical spine (n = 1), while a more diffuse, bilateral enlargement was identified in the lumbar spine (n = 3). Enlargement of the ligament either caused or was a component of spinal stenosis that caused neurologic signs or symptoms. Three of the patients had evidence of calcium pyrophosphate deposition elsewhere. Deposition of calcium pyrophosphate dihydrate within the ligamentum flavum causing either focal or diffuse enlargement can be associated with significant spinal stenosis.