Clinical and experimental studies on permeability of tracers in normal spinal cord and syringomyelia

Delayed CT Myelography (CTM) demonstrated intramedullary cavities in 18 patients, most of which appeared on the 6-hour scan. The attenuation values of the normal spinal cord increased progressively with time, and recorded a peak at 6 hours. The CT numbers of the gray matter of metrizamide were significantly high, as compared with those of iotrol. In the tracer study reported, lanthanum penetrated through the marginal glia to the normal and pathologic spinal cord. Reaction products of horseradish peroxidase (HRP) were mainly in the extracellular space of the normal spinal cord. The pathologic spinal cord, however, allowed the passage of HRP into the parenchyma through the extracellular space of the marginal glia. Consequently, the extracellular space of the spinal cord surface constitutes a pathway for cerebrospinal fluid solutes. Either metrizamide or iotrol thus diffuses into the spinal cord from the subarachnoid space.