Arachnoiditis Ossificans – A Rare Cause of Progressive Myelopathy

Arachnoiditis ossificans is a rare cause of chronic, progressive myelopathy. In contrast to the more common benign causes of meningeal calcification, arachnoiditis ossificans results in replacement of portions of the spinal arachnoid by bone as an end-stage complication of adhesive arachnoiditis. It is usually the sequela of prior trauma or interventional procedures. Prognosis and treatment options depend upon the location and degree of spinal stenosis with thoracic involvement being more common and more severe than lumbar spine involvement. The imaging findings on magnetic resonance imaging may be confusing; however, the findings of intraspinal ossification on computed tomography are characteristics and diagnostic. We present a classic case of arachnoiditis ossificans in an elderly man who presented with progressive myelopathy and a recent fall, along with a review of the literature. The imaging in this case not only identified the characteristic findings of arachnoiditis ossificans but also identified secondary findings of the underlying causative etiology.