Transdural spinal cord herniation: pre- and postoperative MRI findings.

Idiopathic transdural spinal cord herniation (ICSH), a rare condition which may cause progressive myelopathy, can be diagnosed preoperatively by MRI. Surgical treatment usually results in the resolution of symptoms and, thus, familiarity with the imaging findings in this condition impacts patient management. We present the case of a 36-year-old woman in whom the initial MRI findings were thought to be consistent with only an arachnoid cyst compressing the spinal cord. After surgery, her symptoms remained unchanged, and a repeat MRI study was interpreted as being compatible with a transdural spinal cord herniation. Repeated surgery with reduction of the herniation resulted in significant clinical improvement.