Arachnoiditis Ossificans Findings: Severe mass like arachnoiditis throughout the lumbar intrathecal space with peripheral severe clumping of nerve roots at L5-S1. Punctate areas of focal signal drop out consistent with calcification in the arachnoidal adhesions.
Discussion: Arachnoiditis Ossificans is an easy diagnosis by CT but more subtle on MRI as this case shows. The MRI findings of the intrathecal calcification are variable, sometimes with signal drop out as in this case and sometimes bright on T1. It is likely that the patients disc injection in 1973 included an intrathecal component.