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.


Neurosurg Focus. 2007;22(2) 

In This Article

Pathological Features

The wall of a spinal extradural arachnoid cyst usually consists of fibrous connective tissue with an inner single-cell arachnoid lining; however, this lining is sometimes absent on histological examination.[11,22] Spinal arachnoid cysts have been classified into three major categories:[16] extradural cysts without spinal nerve root fibers (Type I), subdivided into extradural arachnoid cysts (Type IA) and sacral meningoceles (Type IB); extradural cysts with spinal nerve root fibers (Type II); and intradural cysts (Type III). In some cases, an extradural cyst can demonstrate substantial intradural extension.[6,7] In nearly all cases of Type IA cysts, communication of CSF between the cyst and the intrathecal subarachnoid space through a dural defect has been reported.[4,6,14,16,19] The case of a noncommunicating spinal extradural arachnoid cyst was recently reported.[13] Intraoperatively, the dura was intact and there was no evidence of communication into the intradural subarachnoid space.


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