Spinal Extradural Arachnoid Cysts: Clinical, Radiological, and Surgical Feature

James K. Liu, M.D.; Chad D. Cole, M.D.; Peter Kan, M.D.; Meic H. Schmidt, M.D.

Disclosures

Neurosurg Focus. 2007;22(2) 

In This Article

Surgical Treatment

For asymptomatic patients, conservative treatment with observation is recommended.[19] The mainstay of treatment in patients with symptomatic neurological deterioration from spinal extradural arachnoid cysts is complete excision of the cyst, followed by obliteration of the communicating pedicle and watertight repair of the dural defect to eradicate the ball-valve mechanism (Fig. 5).[4,10] Total en-bloc removal of a large thoracolumbar Type 1A spinal extradural arachnoid cyst is illustrated in Fig. 5. The patient, a 20-year-old woman, had presented with low-back pain and neurogenic claudication (see preoperative images in Figs. 3 and 4). After a T11-L2 laminectomy, the cyst was carefully dissected off the thecal sac, and the communicating pedicle through the dural defect was identified. The pedicle was ligated with sutures and divided to allow en-bloc removal of the cyst. The dural defect was then oversewn primarily and augmented with a dural onlay allograft and fibrin glue.

Intraoperative photographs showing surgical removal of the spinal arachnoid cyst in the patient whose preoperative images are shown in Figs. 3 and 4. A T11–L2 laminectomy was performed to expose the large extradural spinal arachnoid cyst arising from the dorsal aspect of the spinal canal (A). A plane between the cyst (B, asterisk) and thecal sac (white arrow) can be identified to allow dissection of the cyst from the thecal sac for en-bloc removal (C). This technique allows the cyst wall to be kept intact. Careful dissection is performed to decompress the thecal sac, and the dural defect and communicating pedicle in the subarachnoid space are identified. The pedicle is ligated with sutures (D) and divided to allow en-bloc removal of the cyst (E). A suture ligature is seen where the communicating pedicle was tied off (E). The dural defect is then closed primarily and augmented with a dural onlay allograft and fibrin glue. Postoperatively, the patient's symptoms resolved and she was neurologically intact with no evidence of CSF leakage.

Total excision of the cyst is recommended whenever possible to prevent reaccumulation of the cyst.[11,17,21,24,25,28] These cysts can usually be dissected and elevated off of the dura with ease; however, in cases in which dense fibrous adhesions prevent safe separation of the cyst from the dura, a wide marsupialization of the cyst can be performed by resecting the dorsal wall of the cyst and closing the dural defect.[24,25] Simple drainage of the cyst contents may result in temporary relief only. If the cyst does not communicate with the subarachnoid space, complete excision can be performed without subsequent repair of the dural defect. Although some authors have advocated cyst-to-peritoneal shunting when the dural defect is large and not amenable to watertight repair,[18,19,23] we recommend a trial of patch grafting and fibrin glue repair before considering permanent shunt insertion.

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