Spinal arachnoid cysts
These cysts, of presumed developmental origin, which differ from the neurenteric cyst in not being associated with spina bifida, are an occasional cause of cord compression in children, adolescents, and young adults. Commonly they give episodes of radicular pain with signs of spinal cord dysfunction which develop in a step-like manner. Most lie in the dorsal region posterior to the cord and communicate with the subarachnoid space by a narrow orifice which, when myelography was the principal investigation, used only to be easily demonstrable by supine examination.
MRI, using T1- and T2-weighted images, usually readily demonstrates the cyst-like structure, which has the signal characteristics of CSF; this is also seen in other meningeal cysts. Arachnoid cysts may be particularly common in cases of Marfan's syndrome. Surgical decompression and excision of the cyst is indicated when there is a progressive clinical deficit.