Adhesive arachnoiditis causing cauda equina syndrome in ankylosing spondylitis: CT and MRI demonstration of dural calcification and a dorsal dural diverticulum

Abstract

We present the radiological features of a 42-year-old man with long-standing inactive ankylosing spondylitis (AS), demonstrating that arachnoiditis is a cause of a cauda equina syndrome (CES) in this disease. CT showed a dorsal arachnoid diverticulum causing scalloped erosion of the laminae, and punctate and curvilinear dural calcification. MRI revealed adhesion and convergence of the cauda equina dorsally into the arachnoid pouch, causing the dural sac to appear empty canal. To the best of our knowledge, dural calcification on CT is a new finding in AS, which may be related to the CES. Our findings support the hypothesis that chronic adhesive arachnoiditis with subsequent loss of meningeal elasticity may be the main cause of CES in AS.

Lumbar radiculopathy in ankylosing spondylitis with dural ectasia

“…2,4,8,9,18 Dural ectasia can be symptomatic or asymptomatic. 13 Symptoms may include back pain, radiculopathy and CES in the later phases.…”

“…4 In theory, it is possible that thinning peridural tissues and adhesion of the dura mater to surrounding structures reduces the compliance and the elasticity of the lower thecal sac and its ability to dampen fluctuations in cerebrospinal fluid pressure, resulting in slow development of dural ectasia and bony erosion. 2 Other theories involve demyelination and injury related to previous radiotherapy or vascular insufficiency. 2 It is possible that primary ligamentous inflammation leads to ectasia and erosion of the meninges and dorsal bony elements.…”

“…2 Other theories involve demyelination and injury related to previous radiotherapy or vascular insufficiency. 2 It is possible that primary ligamentous inflammation leads to ectasia and erosion of the meninges and dorsal bony elements. Initial inflammation or subsequent mechanical or vascular abnormalities resulting from adhesions may lead to degenerative changes in the spinal nerves themselves.…”

“…CES is a late and poorly understood complication of AS. [1][2][3][4][5][6][7] This complication has several possible mechanisms, including fibrosis following arachnoiditis, root damage by dural ectasia, and direct compression by arachnoid cyst. Bowie and Glasgow 17 and Hunge 9 independently were the first to report the disorder in 1961.…”

Put Your Back into It: Pathologic Conditions of the Spine at Chest CT

“…Involvement of the lumbar spine with associated cauda equina syndrome has also been reported (4). Although most of the thin linear dural calcifications are incidental, extensive dural calcifications that reduce the anteroposterior dimension of the spinal canal to less than 1.0 cm should prompt the radiologist to recommend correlation for symptoms of spinal stenosis and consideration of magnetic resonance (MR) imaging to evaluate for cord impingement (5).…”