Spinal Extradural Arachnoid Cyst

A spinal extradural arachnoid cyst (SEAC), which is mostly found at the thoracic spine, is a rare disease, accounting for approximately 1% to 3% of spinal tumors. SEAC patients are generally men in their 20’s, 30’s, or 50’s. SEACs are most commonly found in the middle or lower thoracic spine, and less frequently found in the lumbar region, although they can be detected at any lesion of the spine. A SEAC results from a small defect in the dura matter that induces cerebrospinal fluid (CSF) accumulation and arachnoid membrane herniation. The cause of this herniation, which is still under debate, may be either congenital or acquired. The neurological symptoms of a SEAC, including myelopathy, can be triggered by the mass effect of cord or root compression. A SEAC can be enlarged during exercise or other actions because there is small defect between the cysts and subarachnoid space that allows increased cranial pressure to stimulate the flow of CSF from the intradural space to the cyst. A SEAC is a meningeal cyst that can be classified into three major categories. Type I cysts are composed of extradural arachnoid cysts (EAC) without nerve root fibers, Type II cysts are composed of EAC with nerve root fibers, and Type III cysts are composed of intradural meningeal cyst. Type 1 meningeal cysts can be subcategorized as EAC (Type Ia) and sacral meningoceles (Type Ib). A SEAC can be caused by herniation of the dura matter, which can be the result of a congenital anomaly, trauma, infection, or inflammation. However, the causes of such herniation remain unclear. To treat a SEAC, diverse surgical techniques have been introduced, although there is no consensus regarding the most reasonable treatment. Most investigators agree that the dural defect must be repaired, but total removal of a Spinal Extradural Arachnoid Cyst