Spinal extradural arachnoid cysts (SEAC) are relatively rare and usually asymptomatic. They preferentially are situated in the thoracic extradural space, and almost always dorsal. SEACs may present with back pain and/or cord compression symptoms. Needle aspiration, needle fenestration or open surgical resection/fenestration have been reported as treatment modalities.We present a 35-year-old woman who complained of radiating pain from the right lower thoracic region of her back towards the right inguinal region which was aggravated upon defecation and straining. MRI revealed an extradural cyst located laterally at T11-12 level on the right, with a nerve root herniation. During a T11-12 hemilaminectomy, upon resection of the cyst wall, a nerve root was noted to be herniating into the cyst cavity through a dural defect. The nerve root was released and repositioned intradurally, followed by direct suture of the dural tear. Histological findings of the cyst wall confirmed an arachnoid cyst. Postoperative course was uneventful without complications. Postoperative MRI confirmed a complete resection of the cyst. Five years after surgery, the patient is asymptomatic with complete recovery.Thoracic EACs can present with radiating pain due to a transdural herniation of a thoracic nerve root into the cyst, potentially due to a mechanism of intermittent pressure gradients between the intradural and extradural spaces. MRI can prove beneficial in visualizing the nerve prolapsing into the cyst. Open resection of the cyst wall, reduction of the nerve root herniation, and subsequent direct closure of the dural tear led to complete recovery.

作者：Nagesh C, Shanbhag；Ruurd F, Duyff；Rob J M, Groen

来源：World neurosurgery 2017 年