Thoracolumbar Spinal Extradural Arachnoid Cysts

Abstract

To the Editor: The article by Funao et al1 was interesting and informative. The authors describe their experience with treating thoracolumbar spinal extradural arachnoid cysts (SEAC) in 12 patients. Seven patients underwent laminectomies and total cyst resection and closure of the dural defect, and 5 patients underwent selective laminectomy at the preoperative identified communication site. In the latter group, the cyst wall was violated dorsally following which an endoscope was introduced confirming the location of the dural communication which was then sutured. Neurological outcome was excellent in both groups and there was no difference in postoperative neurological recovery between the 2 surgical procedures. The only difference was a greater increase in the postoperative kyphotic angle in patients treated with laminectomy and total cyst resection, with a 9.7° change vs a 2.2° change in the laminotomy group. All 12 patients had neurological complaints with lower extremity numbness being the most common. Some of the patients also had associated back pain. The question arises whether or not to treat patients who present solely with back pain as it seems to be challenging to ascribe the extradural cyst as the pain generator. As the authors state the benefits of myelography in diagnosing SEAC was first described in 19622 by the past Chair of Neurosurgery at the University of Iowa in 1962, George Perret. Even with myelography identifying the site of the dural defect can be elusive, hence misguiding the placement of the laminotomy. Collapsing the cyst wall with the introduction of the endoscope might also impair visualization and identification of the dural defect. In these instances a laminectomy and exploration with proper identification of the dural defect is appropriate. Lastly, we have been treating these cysts with total resection and dural ligation through multilevel laminoplasty. This is an alternative method to a laminectomy with a lower risk of postoperative kyphosis and deformity. We also have observed that the incidence of postoperative cerebrospinal fluid leak is lesser with laminoplasty in intradural spine operations compared to laminectomy. Laminoplasty is an acceptable, and can be an attractive option for excision of the cyst, and ligation of the defect when the latter is not clearly identifiable. We congratulate the authors on this well written and informative article. Disclosure The content of this article has not been published elsewhere in any form. There are no financial disclosures and no conflicts of interest for any of the listed authors of this article.