Magnetization transfer imaging of patients with definite MS and negative conventional MRI

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Abstract
Objective: To assess, in a group of patients with clinically or laboratory-supported definite MS and negative conventional MRI scans of the brain, whether magnetization transfer imaging (MTI) is able to detect subtle white matter changes. Background: MTI of the brain in patients with MS frequently demonstrates the presence of microscopic damage to white matter, which appears normal on conventional MRI. Methods: Brain MRI and MTI scans were obtained from 11 patients with negative conventional MRIs of the brain, selected from 618 clinically or laboratory-supported definite MS cases scanned in the last 2 years in three Italian MS centers. Results: Compared with control subjects, patients had significantly lower mean MT ratios (MTR) in the pons, cerebellum, and periventricular regions. The percentages of pixels with MTR values below 1, 2, and 3 SD of the mean MTR value of the control subjects were 7.6% (range, 3.2% to 11.8%), 5.2% (range, 2.0% to 8.5%), and 3.6% (range, 1.2% to 6.1%), respectively. They were mainly located in the white matter of the centra semiovalia, and usually were isolated. Conclusions: MTI can detect white matter abnormalities in patients with MS and negative conventional brain MRI scans. The detection of such abnormalities may increase diagnostic confidence in those cases where MS is clinically suspected, but conventional MRI does not suggest the diagnosis.