To the Editor.
—Capra et al1 should be widely congratulated for their elegant study of gadolinium-pentetic acid enhancing (GAD+) lesions in 10 patients with relapsing-remitting multiple sclerosis (MS) whose serial brain and spinal cord magnetic resonance imaging (MRI) scans and neurological examinations were monitored for 3 months. This study significantly advances our understanding of GAD+ lesion activity in patients with MS because both brain and spinal cord locations were simultaneously monitored and careful attention to repositioning on serial scans was done with the assistance of a laser. However, the results of this study should be interpreted with some caution because, even with laser assistance, the potential for unavoidable small repositioning errors (<2 degrees) between the serial scans is still present. The effects of repositioning error in this study, or for that matter any previously published uncontrolled serial MRI study in patients with MS, have still not been adequately assessed.
Goodkin DE, Vanderburg-Medendorp S, Ross J. The Effect of Repositioning Error on Serial Magnetic Resonance Imaging Scans. Arch Neurol. 1993;50(6):569–570. doi:10.1001/archneur.1993.00540060011007
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