Posttraumatic Arachnoid Cyst in the Thoracic Spine with Medullary Compression: Case Report.

Arachnoid cysts are rare; they can occur at all levels of the dural sac, and can have a congenital, traumatic, iatrogenic or inflammatory origin. In the present article, we report a patient presenting a compressive thoracic myelopathy due to an unusual intradural arachnoid cyst with posttraumatic manifestation and its resolution, in addition to a literature review on the subject. These cysts mainly occur at the thoracic spine, followed by the lumbar, lumbosacral and thoracolumbar spines. Traumatic cysts are caused by an injury to the inner dural layer. These lesions produce neurological deficits through a mass effect on the spinal cord. Concomitant compressive myelopathy is even rarer. In case of myelopathy, cyst resection or drainage is the treatment of choice, and it must be performed immediately. Although rare, arachnoid cysts can be a complication of spine fractures; as such, orthopedists and neurosurgeons, who commonly see these injuries, must be prepared for this unusual situation.