Spinal extradural arachnoid cyst following percutaneous vertebroplasty

We report a rare complication of extradural arachnoid cyst following percutaneous vertebroplasty in a spinal metastasis patient. Percutaneous vertebroplasty has been established as a safe and effective treatment for osteoporotic vertebral fractures and vertebral metastatic lesions. To our knowledge, extradural arachnoid cyst following vertebroplasty has not been reported in literature. A 48-year-old woman diagnosed with adenocarcinoma underwent percutaneous vertebroplasty at the L3 vertebral level due to painful solitary spinal metastasis. At 5 months after surgery, the patient complained of low back pain radiating to the left lower extremity. MRI showed a large cystic lesion in the spinal canal at the L2-L3 level with compression to adjacent dura sac. On T1- and T2-weighted images, the signal within the cyst had the same intensity as cerebrospinal fluid. The patient underwent laminectomy for excision of the extradural cyst. Intraoperatively, a small communication between the cyst and the subarachnoid space was seen at the level of the L3 pedicle. Pathological examination revealed that the cyst wall was composed of non-specific fibrous connective tissue and the content of the cyst was the same as that of cerebrospinal fluid. Postoperatively, the patient's symptom was relieved immediately. The iatrogenic dural injury produced by puncture of the pedicle during vertebroplasty may be the cause of formation of the extradural arachnoid cyst.