Syringomyelia associated with intradural extramedullary masses of the spinal canal.

Three cases of syringomyelia associated with intradural extramedullary tumors of the spinal canal are reported to demonstrate their radiographic feature, to postulate a mechanism for their formation, and to describe the clinical deterioration occurring in two patients immediately after metrizamide myelography. It is believed that the mechanism by which these syrinx cavities formed was similar to the mechanism of syrinx formation within chronically injured spinal cords. The cystic cavities may extend for considerable distances away from the extramedullary mass and may be present above and/or below the mass. The development of a syringomyelia in the face of an intradural extramedullary tumor may not be rare, and it is suspected that with the more frequent use of delayed metrizamide CT and now magnetic resonance imaging, syringomyelia will be found as an occasional consequence of this type of mass.