Spinal intradural arachnoid cyst as a complication of insertion of an interspinous device.

Spinal intradural arachnoid cysts (SACs) account for approximately 10% of total arachnoid cysts, and iatrogenic attribution is rare. A 50-year-old male presented with low back pain and severe radiating pain in his right leg along the S1 dermatome. He had an interspinous device (ISD) inserted 10 years earlier. Plain radiographs showed breakage and angular movement of the ISD at L4/5. Magnetic resonance imaging (MRI) of the lumbosacral spine disclosed multiple intradural cystic tumors in the entire lumbar region. He underwent removal of the ISD, laminectomy, and resection of the intradural cyst. The pathologic finding of the cystic tumor was compatible with arachnoid cyst. Antibodies to parasites, including cysticercosis, were negative in both the serum and cerebrospinal fluid (CSF). The ventral surface of the implant was clearly broken.