Spinal extradural arachnoid cyst in aging spine

Abstract

A 67-year-old man presented with complaints of low back pain associated with bilateral claudication and weakness of both feet of 15 months' duration. Physical examination revealed an increase of osteotendinous reflexes in both legs and Babinski sign. Magnetic resonance imaging examination showed a cystic lesion with regular contour from T12 to L2. The lesion was hypointense on T1-weighted image and hyperintense on T2-weighted image; it was homogenous with cerebrospinal fluid, with no contrast enhancement noted (Fig. 1). Medullary cone and cauda equina were compressed dorsally (Fig. 2). The patient was surgically managed and the diagnosis was spinal extradural arachnoid cyst and lumbar canal stenosis. Spinal arachnoid cysts are uncommon, accounting for about 1% of all spinal tumors [ [1] Chae K.H. Kim S.W. Shin H. Septated extradural arachnoid cyst in thoracolumbar spine causing myelopathy. J Korean Neurosurg Soc. 2006; 40: 381-383 Google Scholar ]. Spinal arachnoid cysts occur most frequently in the thoracic spine (65%), followed by the lumbosacral spine (3%), and the thoracolumbar spine (3.3%). Most of the lesions are located posteriorly in the spinal canal [ [1] Chae K.H. Kim S.W. Shin H. Septated extradural arachnoid cyst in thoracolumbar spine causing myelopathy. J Korean Neurosurg Soc. 2006; 40: 381-383 Google Scholar ]. Its etiology remains uncertain. Most non-traumatic spinal extradural arachnoid cysts are thought to be congenital; nevertheless, arachnoid pouching through a possibly congenital dural defect and enlargement of the cyst caused by a one-way valve is the most accredited theory [ [2] Liu J.K. Cole C.D. Kan P. Schmidt M.H. Spinal extradural arachnoid cysts: clinical, radiological and surgical features. Neurosurg Focus. 2007; 22: 1-5 Crossref Scopus (80) Google Scholar ]. Fig. 2Axial T2-weighted image (Top) from T12 shows compression of the medullary cone (arrow) dorsally. Axial T2-weighted image (Bottom) from L1 shows cauda equina ventralized (arrow). View Large Image Figure Viewer Download Hi-res image