Assessment of disease activity in multiple sclerosis phenotypes with combined Gadolinium- and superparamagnetic iron oxide-enahced MR imaging

To compare magnetic resonance (MR) imaging features
of multiple sclerosis (MS) lesions after the administration
of a gadolinium-based contrast agent and ultrasmall superparamagnetic
iron oxide (USPIO) particles among the
clinical phenotypes of MS and over time.
Materials and
Methods:
This study was approved by the local ethics committee, and
written informed consent was obtained from all patients.
Twenty-four patients with MS (10 with relapsing and 14 with
progressive forms) underwent clinical and gadolinium- and
USPIO-enhanced MR examinations at baseline and 6-month
follow-up. The number of lesions that enhanced with gadolinium
alone, USPIO alone, or both was compared with the
Pearson x2 or Fisher exact test, and lesion sizes were compared
with the Wilcoxon Mann-Whitney U test. At 6-month
follow-up, the lesion signal intensity on precontrast T1-
weighted images and the enhancement after repeat injection
of the contrast agent were compared with the baseline
postcontrast imaging features by using the McNemar test.
Results: Fifty-six lesions were considered active owing to contrast
enhancement at baseline; 37 lesions (66%) in 10 patients
enhanced with gadolinium. The use of USPIO helped detect
19 additional lesions (34%), and two additional patients
were classified as having active disease. Thus, the use
of both agents enabled detection of 51% (19 of 37 lesions)
more lesions than with gadolinium alone. Enhanced lesions
were more frequently observed in the relapsing compared
with the progressive forms of MS (P , .0001). USPIO enhancement,
in the form of ringlike patterns, could also be
observed on T1-weighted images in patients with progressive
MS, enabling the detection of five lesions in addition to the
five detected with gadolinium in this phenotype. Lesions that
enhanced with both contrast agents at baseline were larger
(mean size, 6.5 mm 6 3.8; P = .001) and were more likely
to persistently enhance at 6-month follow-up (seven of 27
lesions, P , .0001) compared with those that enhanced only
with gadolinium (mean size, 4.9 mm 6 2.2; one of nine lesions)
or USPIO (mean size, 3.5 mm 6 1.5; 0 of 17 lesions).
Conclusion: The combination of gadolinium and USPIO in patients
with MS can help identify additional active lesions compared
with the current standard, the gadolinium-only approach,
even in progressive forms of MS. Lesions that
enhance with both agents may exhibit a more aggressive
evolution than those that enhance with only one contrast
agent.