Spinal cord herniation into an extensive extradural meningeal cyst: postoperative analysis of intracystic flow by phase-contrast cine MRI.

We report a patient with idiopathic spinal cord herniation who underwent postoperative myelography and phase-contrast cine magnetic resonance imaging (MRI) to clarify the condition of the ventral cystic lesion into which the spinal cord had been herniated. This 58-year-old man showed symptoms and signs compatible with Brown-Séquard syndrome. A myelogram and MRI showed that the spinal cord was incarcerated in a small space, and this finding led to the diagnosis of spinal cord herniation. In the operation, the herniated spinal cord was returned to the initial intradural space, and the dural defect was enlarged to prevent recurrence of the herniation. After the operation, leg muscle strength improved and bladder and bowel dysfunction resolved, but analgesia was unchanged. Postoperative myelography revealed a very large extradural cystic lesion, which extended from C2 to L1 vertebral level. A cerebrospinal fluid (CSF) flow study of the intradural space disclosed a near-normal pattern, but the intracystic CSF dynamics were abnormal. In the intracystic space at just the upper level of the lesion, cranial flow (reverse directional flow in comparison with the intradural flow) was seen in the systolic cycle after momentary fast caudal flow, and these CSF dynamics may have been related to the spinal cord herniation.