Spinal extradural arachnoid cyst

Abstract

Spinal extradural arachnoid cyst (SEAC) is a rare disease and uncommon cause of compressive myelopathy. The etiology remains still unclear. We experienced 2 cases of SEACs and reviewed the cases and previous literatures. A 59-year-old man complained of both leg radiating pain and paresthesia for 4 years. His MRI showed an extradural cyst from T12 to L3 and we performed cyst fenestration and repaired the dural defect with tailored laminectomy. Another 51-year-old female patient visited our clinical with left buttock pain and paresthesia for 3 years. A large extradural cyst was found at T1-L2 level on MRI and a communication between the cyst and subarachnoid space was illustrated by CT-myelography. We performed cyst fenestration with primary repair of dural defect. Both patients' symptoms gradually subsided and follow up images taken 1-2 months postoperatively showed nearly disappeared cysts. There has been no documented recurrence in these two cases so far. Tailored laminotomy with cyst fenestration can be a safe and effective alternative choice in treating SEACs compared to traditional complete resection of cyst wall with multi-level laminectomy.

Keywords: Arachnoid cyst; Cerebrospinal fluid; Thoracolumbar spine.

Fig. 1

Preoperative and postoperative images of case 1. A and B : A large, extradural cystic lesion is found at T12-L3. Adjacent bony structures are thinned due to long standing growth of the lesion and it is confirmed by CT images. C : Postoperative 1month MRI reveals totally disappeared cystic lesion with cord expansion.

Fig. 2

Preoperative images of case 2. A : an elongated cystic lesion is located posterior to the spinal cord at T11-L2 and the cord is displaced to ventral side. B, C, and D : Contrast dye spreaded up to T11 body level and filled the cyst at the level and further diffusion over the upper level was scanty. We assumed that the leak point might be located at T10-11 or T11-12 level and there might be any communication or dural defect at the leak point.

Fig. 3

introperative microscopic photography of case 2. A : On bony exposure, thinned, transparent cystic membrane (white arrow) is found. B : A single rootlet of right T12-L1 level (black arrow) is protruding through a dural defect.

Fig. 4

Histologic finding of case 2. the histologic finding is consistent with arachnoid cyst that is characterized by layered collagenous fibers and a membrane with flat lining cells (H&E, original magnification ×100).

Fig. 5

Postoperative MRI of case 2. posteoperative 2 month MRI shows nearly disappeared cyst.