Coexisting protruding osteocyte and arachnoid cyst mimicking spinal cord herniation in a patient with Brown Sequard syndrome

Abstract This 68-year-old man presented with progressive spastic paraparesis of 2-month duration. The diagnosis was Brown-Sequard syndrome(BSS). Magnetic resonance imaging (MRI) revealed ventral displacement of the spinal cord at Th 7–8. The spinal cord deformity was dominant on the left side. He underwent surgery under the preoperative diagnosis of spinal cord herniation at Th 7–8. Intraoperatively we detected an arachnoid cyst and an osteophyte that compressed the spinal cord at Th 7–8 dorsally and ventrally rather than spinal cord herniation. Postoperative MRI showed successful spinal cord decompression. His neurological findings improved remarkably just after surgery. Although the misdiagnosis of spinal hernia in the actual presence of arachnoid cysts has been reported, ours is the first case of both, a lateralized osteophyte and an arachnoid cysts mimicking spinal cord herniation.