Radiologic imaging of symptomatic ligamentum flavum thickening with and without ossification

Thickening of the ligamenta flava with and without ossification in the thoracic and lumbar regions is a frequent finding on CT scanning; however, it is not widely appreciated as a possible primary cause of compressive cord, cauda equina, and nerve-root symptoms. We present observations from a series of seven patients whose symptoms were caused exclusively or largely by thickened ligamenta flava in the thoracic and lumbar regions. The findings were best demonstrated on myelography. One of our cases had been missed on previous MR, as would be expected with the null signal of calcification. CT scanning necessitates an extended window to ensure discrimination of an ossified ligament from thecal metrizamide. Thickened ligamenta flava are often found in conjunction with degenerative disease and spinal stenosis at multiple levels and should not be ignored as a possible major contributing factor to the patient's symptoms. In addition, those patients with a secondary block from a thickened ligamentum flavum should be studied from above with C1-C2 puncture to rule out other levels of clinically significant disease. Attention to the particular findings of thickened ligamenta flava is important since surgical intervention must involve removal of the entire offending ligament(s); otherwise clinical symptoms may not be relieved.