Idiopathic transverse myelitis: MR characteristics.

PURPOSE To describe the MR characteristics that can distinguish idiopathic transverse myelitis from other intramedullary lesions. METHODS A total of 32 initial and follow-up MR studies in 17 patients with clinically proved transverse myelitis were reviewed retrospectively. The location, size, pattern, and segmental length of areas of hyperintensity were estimated on T2-weighted axial and sagittal images. In 15 of the patients, whose neurologic abnormalities were limited to the spinal cord, the location and pattern of intramedullary contrast enhancement were evaluated on sagittal and axial T1-weighted images. Follow-up MR studies were available for 10 patients. The statistical significance of cord enhancement between the groups with and without cord expansion was calculated. RESULTS Common MR findings of idiopathic transverse myelitis included a centrally located hyperintensity occupying more than two thirds of the cross-sectional area of the cord (88%); a length of 3 to 4 vertebral segments (53%), with variable presence of cord expansion (47%); a small central area of intensity, isointense with normal cord, in the core of hyperintensity (47%); focal, peripheral cord enhancement (53%), particularly in patients with cord expansion; and a slow regression of T2 hyperintensity with an enhancing nodule. Although no linear correspondence was observed between MR findings and neurologic signs and symptoms, all but 4 patients improved clinically as MR findings improved or remained stable. CONCLUSIONS MR findings are helpful in detecting transverse myelitis and in differentiating this entity from multiple sclerosis and cord tumors, but clinical assessment and observation of MR changes over time are essential in making the diagnosis.