Cerebrospinal fluid pulsation in patients with Marfan syndrome may dilate the dural sac, causing dural ectasia. This condition, which may be identified in more than 90% of patients, is considered a specific sign of the disease and is usually asymptomatic.1 Rarely, dural ectasia is associated with sacral arachnoid cysts, which may cause lumbosacral root compression with pain and sphincteric disturbance.2 Herein, we report a 25-year-old man with Marfan syndrome who presented with a 2-year history of worsening distal sensory motor deficits of the lower limbs. Clinical examination showed bilateral clawfoot (Figure 1) with weakness of the distal muscles and hypoesthesia below the L4 level. Electromyography showed denervation in the distal lower limb muscles. Magnetic resonance imaging of the spine showed a large intraspinal, cerebrospinal fluid–containing cyst that displaced ventrally the thecal sac and the conus medullaris (Figure 2). In the sagittal T2-weighted images, the upper pole of the cyst was at level Th11-Th12 and the lower pole, at the midlevel of L4; a faint linear image was seen in the cerebrospinal fluid–containing cyst and both 3-dimensional fast imaging using steady-state acquisition magnetic resonance–myelography and axial, high-resolution, T2-weighted images confirmed the presence and the location of the septum and the displacement of the dural sac. The final diagnosis was extradural arachnoid cyst (Figure 2).
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The lower limbs of the patient showing bilateral clawfoot.
Magnetic resonance imaging of the spine. A and B, Adjacent sagittal T2-weighted images show the posterior extradural cyst extending from Th11-Th 12 to the L4 level, expanding the spinal canal. The dural sac and the tip of the conus medullary (arrow) are ventrally displaced. Note the normal course of the lumbosacral roots at the L4-L5 level. There is also a disk herniation at level L2-L3. C, Sagittal 3-dimensional fast imaging using steady-state acquisition sequence clearly demonstrates that a thin septum (double arrows) divides the cyst. D-F, Axial T2-weighted images at level L1 (D), L2 (E), and L3 (F) confirm the presence and the course of the cyst septum (double arrows) and the displacement of the dural sac and the tip of the conus medullaris (arrow).
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