Arachnoiditis ossificans

Coronal T2- weighted images shows diffuse abnormal circumferential thickening of thecal sac with blooming artifact, concordant with dural calcifications seen on CT images.

Axial T2- weighted-weighted images shows displacement of the nerve roots of the cauda equina in the initial images. Abnormal thickening and clumping of the cauda equina with intrathecal hypointense signal abnormality seen at distal lumbar, consistent with sequelae of arachnoiditis.

Well defined hyperintense lesion within L4 vertebra body in keeping with a vertebral hemangioma.

Based on CT and MRI findings, features consistent with arachnoiditis ossificans.

Arachnoiditis ossificans is an unusual chronic meningeal inflammatory process.

Is and is thought to be the sequela of end-stage adhesive arachnoiditis.

Common causative factors include surgery, arachnoid hemorrhage, myelography (particularly oil-based contrast agents), and spinal anesthesia.

CT and MRI are complementary imaging techniques.

CT is the best investigation tool to visualize the ossified intraspinal lesion and nerve roots. The findings of ossified intrathecal lesions are specific and diagnostic. As in this case, there is curvilinear dura calcifications, intrathecal coarse calcifications and ossified individual nerve roots adhered to the posterior thecal sac.

The MR imaging is favourable in depicting arachnoiditis. The sign includes central clumping of nerve roots, peripheral adhesion of the nerve roots and intradural cysts due to loculation of the subarachnoid spaces.