The ependymal "Dot-Dash" sign: an MR imaging finding of early multiple sclerosis.
Corpus callosum lesions are of specific interest in the evaluation of suspected multiple sclerosis in brain MR imaging. Using thin-section sagittal fluid-attenuated inversion recovery images, researchers have shown that the finding of "subcallosal striations" correlates significantly with the diagnosis of multiple sclerosis. Using the same MR imaging technique, we describe a finding of ependymal irregularity that we call the "Dot-Dash" sign, which we believe to be associated with early multiple sclerosis. Sagittal 2-mm fast fluid-attenuated inversion recovery images were obtained in 70 patients. Thirty-five patients had multiple sclerosis according to the Poser criteria, and 35 were age-matched controls. The images were reviewed in a blinded fashion by an experienced neuroradiologist for the presence or absence of the Dot-Dash sign. The correlation between the Dot-Dash sign and definite clinical multiple sclerosis is highly significant (P < .001), with a sensitivity of 91.4% and a specificity of 65.7%. In the age group of < or =50 years, the sensitivity was 95.7% and the specificity, 71.9%. The Dot-Dash sign of ependymal irregularity on thin-section sagittal fluid-attenuated inversion recovery images is an early marker for multiple sclerosis, which is particularly useful in the younger patient. This finding appears to be more sensitive for early lesion detection than any other multiple sclerosis imaging finding yet described in the literature.