Introduction: To elucidate the origin of syrinx fluid, we performed a prospective study using CT-myelography to evaluate transport of CSF into the syrinx in different kinds of syringomyelia.
Methods: Patients with Chiari I-type syringomyelia (N=19) or primary spinal syringomyelia (N=11) were studied before and 1 week after decompressive surgery, and patients with intramedullary hemangioblastoma (N=8) were studied only before tumor removal. CT scans were performed through the syrinx before and 2, 4, 6, 8, 10 and 22h after dye injection.
Results: Dye density within the subarachnoid space and syrinx was measured in Hounsfield Units (HU). Maximal measurements in the syrinx in Chiari I-related (114+/-14 HU, mean+/-SE) and primary spinal syringomyelia (132+/-18) were greater than in tumor-related syringomyelia (69+/-20; p=0.017; p=0.006; respectively, unpaired t test). Dye transport into the syrinx 1 week after surgery (Chiari I, 86+/-12 HU; primary spinal, 65+/-17) was less than before surgery (p=0.04; p=0.03; respectively, paired t test). In addition, after surgery less contrast entered the spinal cord interstices.
Conclusions: Dye transport into the syrinx in syringomyelia associated with obstruction of CSF pathways (Chiari I and primary spinal) was far greater than in syringomyelia associated with intramedullary tumor. Opening of obstructed CSF pathways reduced transmural passage of CSF into the syrinx and resolved Chiari I-type and primary spinal syringomyelia. Tumor-related syringomyelia resolved with tumor removal. These findings are consistent with syrinx fluid originating from the subarachnoid space in Chiari I-type syringomyelia and primary spinal syringomyelia, and from the tumor in tumor-related syringomyelia.
Patient Care: This research supports treatment of syringomyelia by correcting the primary process that leads to syringomyelia rather than by draining the syrinx using myelotomy and shunting.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the types of conditions that are associated with the development of syringomyelia, 2) Discuss, in small groups, the origin of syrinx fluid, 3) Identify effective treatments for various kinds of syringomyelia.