Cognitive Implications of Deep Gray Matter Iron in Multiple Sclerosis.

G Blevins,H Sun,J.A Kmech,E Fujiwara,P Seres,D Cobzas,A.H Wilman

doi:10.3174/ajnr.a5109

Abstract

Deep gray matter iron accumulation is increasingly recognized in association with multiple sclerosis and can be measured in vivo with MR imaging. The cognitive implications of this pathology are not well-understood, especially vis-à-vis deep gray matter atrophy. Our aim was to investigate the relationships between cognition and deep gray matter iron in MS by using 2 MR imaging-based iron-susceptibility measures. Forty patients with multiple sclerosis (relapsing-remitting, n = 16; progressive, n = 24) and 27 healthy controls were imaged at 4.7T by using the transverse relaxation rate and quantitative susceptibility mapping. The transverse relaxation rate and quantitative susceptibility mapping values and volumes (atrophy) of the caudate, putamen, globus pallidus, and thalamus were determined by multiatlas segmentation. Cognition was assessed with the Brief Repeatable Battery of Neuropsychological Tests. Relationships between cognition and deep gray matter iron were examined by hierarchic regressions. Compared with controls, patients showed reduced memory (P < .001) and processing speed (P = .02) and smaller putamen (P < .001), globus pallidus (P = .002), and thalamic volumes (P < .001). Quantitative susceptibility mapping values were increased in patients compared with controls in the putamen (P = .003) and globus pallidus (P = .003). In patients only, thalamus (P < .001) and putamen (P = .04) volumes were related to cognitive performance. After we controlled for volume effects, quantitative susceptibility mapping values in the globus pallidus (P = .03; trend for transverse relaxation rate, P = .10) were still related to cognition. Quantitative susceptibility mapping was more sensitive compared with the transverse relaxation rate in detecting deep gray matter iron accumulation in the current multiple sclerosis cohort. Atrophy and iron accumulation in deep gray matter both have negative but separable relationships to cognition in multiple sclerosis.

Highlights

BACKGROUND AND PURPOSEDeep gray matter iron accumulation is increasingly recognized in association with multiple sclerosis and can be measured in vivo with MR imaging
Quantitative susceptibility mapping values were increased in patients compared with controls in the putamen (P ϭ .003) and globus pallidus (P ϭ .003)
After we controlled for volume effects, quantitative susceptibility mapping values in the globus pallidus (P ϭ .03; trend for transverse relaxation rate, P ϭ .10) were still related to cognition

Summary

Objectives

Our aim was to investigate the relationships between cognition and deep gray matter iron in MS by using 2 MR imaging– based iron-susceptibility measures. The objective of our study was to determine whether cognition in MS, measured by the Brief Repeatable Battery of Neuropsychological Tests, is related to DGM iron accumulation measured with R2* and QSM at a high field strength (4.7T)

Methods

Results

Discussion

Conclusion