MR in evolution: applications of new technology.

The rapid evolution of MR technology and its application to spine imaging are demonstrated in the paper by Enzmann and his coauthors in this issue of the journal [1]. Their use of standard spin-echo and flow-sensitive pulse sequences show that, in certain cases, the radiologist can no longer be satisfied with describing MR findings as if the pathologic processes were static in nature. Instead , he must try to demonstrate the dynamic state of these entities so that the information can be used in improving patient care. . The description of syringomyelia, both in that article and in an earlier paper by Sherman et al. [2] , indicates how our understanding of a disease changes with technological advances . Older techniques used to diagnose and characterize syringomyelia included air myelography, in which a collapsing cord could be demonstrated, myelocystography, in which the characteristics of the cyst wall could be seen, and metrizam-ide CT, in which accumulation of contrast medium within an intramedullary cyst could be identified. Since all these studies are invasive, the CSF dynamics and hence the natural path-ologic state of these cysts were altered in some degree simply by performing the examination. This is analagous to the uncertainty principle, which states that an observation requires an interaction between the observer and the object being observed and as a result the object itself is disturbed. The introduction of a needle into a thecal sac or into a spinal cord cyst is an obvious example of an observer altering the object under investigation. Many of the conclusions that were reached in the past concerning syringomyelia may have been erroneous because of this intervention. With MR , however, and particularly with the methods described by Enzmann et aI. , we can learn more about the CSF dynamics involved in the various forms of syringomyelia because we can look at the disease in a relatively undisturbed state. There are, as a result, clear implications for diagnosis, treatment, and follow-up of this disease. Correlating levels of active pulsation with the clinical symptoms, differentiating myelomalacia from non pulsatile cysts, recognizing those portions of a syrinx cavity under active expansion, and determining the efficacy of shunt placement are all important observations , regardless of the underlying cause of the syringo-myelia. As one practical example, this information can be significant in evaluating the chronically injured spinal cord. When there is progressive loss of neurologic function in …