An instance of an atypical intraspinal cyst presenting as S1 radiculopathy: a case report and brief review of pathophysiology.

Intraspinal cysts are rare, but typically they originate from a degenerate zygapophyseal joint. These cysts have been commonly referred to as juxtafacet cysts and occur concomitantly with lumbar and occasionally lower-limb radicular pain. Documented cases have shown pseudoarthroses developing from nonhealing pars defects. Histologic analyses have found synovial tissue within these fibrocartilaginous accumulations. We present a case of S1 radiculopathy indicated by an intraspinal pseudocyst arising as a complication of a chronic spondylolytic defect. A brief review of the related pathophysiology is also included.