MR studies of the spinal cord in patients with multiple sclerosis: what should we do?

In this issue of the AJNR, Rocca et al (page 1710) report a comparison of three imaging techniques for detection of plaques in patients with definite multiple sclerosis (MS). They find that a fast short tau inversion recovery (fast STIR) technique was superior to a fast spin-echo (FSE) and a magnetization transfer–prepared gradient-echo (MTGE) approach. The fast STIR images showed the largest number of lesions, and lesions that were visible with FSE or MT-GE were almost always apparent with fast STIR. This confirms the findings of an earlier investigation by Hittmair and colleagues (1) that reported fast STIR to be a highly sensitive technique, but contradicts Thorpe’s results (2) citing similar performance for fast STIR and FSE. As the authors of the current article note, there have been many studies of sensitivity of pulse sequences for detection of MS plaques, with MTGE, FSE, fluid-attenuated inversion recovery (FLAIR), and conventional spin-echo (SE) yielding inconsistent results (3–5). These earlier works, and the results reported by Rocca and colleagues, raise the question of which imaging approach should be used for evaluation of patients with suspected or known MS. In order to answer this question, we must decide what we are seeking. If the goal is to detect the largest number of candidate lesions, then the methods employed by Rocca et al, and by others who have conducted similar studies, are appropriate. The sequence that reveals the largest number of possible lesions will be considered best. This ‘‘more is better’’ approach is appropriate only if one can assume that detecting the largest number of lesions is useful and, by implication, that most or all abnormalities found on these images truly represent MS plaques. There are, however, reasons to suspect that the highest lesion count may not be the best measure of imaging performance in evaluation of MS, and that at least some of the lesions detected may represent false-positive results.