Background: Arachnoiditis ossificans (AO) is a rare entity characterized by the presence of calcified plaques formed by the metaplasia of arachnoid cells. Over 50 cases of AO have been reported, with predisposing factors including spinal trauma, hemorrhage, vascular abnormalities, and infection. The administration of oil-based contrast during myelography as an independent risk factor or in conjunction with other spinal pathology has been described in 9 cases.
Case description: A 70-year-old woman presented for neurosurgical consultation in 2013 with a 2-year history of progressive midthoracic pain, right-sided chest wall allodynia, lower extremity weakness, and gait ataxia. Approximately 30 years ago, she received an oil-based contrast myelogram for investigation of spontaneous spinal hemorrhage. The procedure was well tolerated, and the patient experienced no allergic, hemorrhagic, traumatic, or infectious complications. No etiology was found for the spinal hemorrhage, and the patient recovered fully from that episode. Magnetic resonance imaging (MRI) of the thoracolumbar spine demonstrated multiple compressive intradural lesions in the upper thoracic spine and ventral tethering of the spinal cord at T7. MRI also demonstrated syringomyelia throughout the thoracic spine. Initially, the diagnosis of epidural mass or diastematomyelia was considered. To further characterize the epidural lesion, an unenhanced computed tomography (CT) scan was obtained, demonstrating a long segment of extensive calcification in the periphery of the thoracolumbar spine, with near-complete circumferential involvement from T5 to T11. The diagnosis of AO with extensive thoracic spine calcifications, syringomyelia, and spine cord tethering was made and confirmed at surgery.
Conclusions: In addition to acute inflammation, oil-based contrast myelography also leads to arachnoiditis, calcification, and retained mass lesions because of its chronic inflammatory properties and slow resorptive rate. Three decades after its replacement with water-based contrast material, the chronic sequelae of oil-based contrast myelography may continue to manifest clinically and on CT imaging. Because of calcifications often encasing the spinal cord or nerve roots, management of AO is challenging, and neurologic deficits may persist even after surgery.
Keywords: Arachnoiditis; Calcinosis; Contrast; Inflammation; Myelography; Ossification; Syringomyelia.
Copyright © 2019 Elsevier Inc. All rights reserved.