Mapping of Iron Deposition in Conjunction With Assessment of Nerve Fiber Tract Integrity in Amyotrophic Lateral Sclerosis

Purpose: To test if and where increased iron accumulation occurs in amyotrophic lateral sclerosis (ALS) by quantitative mapping of iron deposition and to relate these findings to white matter tract degeneration assessed by diffusion tensor imaging (DTI). Materials and Methods: Fifteen patients with ALS and 15 age- and gender-matched controls underwent MRI of the brain to obtain R-2* relaxation rate and DTI measurements, focusing on the corticospinal tract (CST) and on deep gray matter structures, using tract-based spatial statistics (TBSS). Results: Compared with controls, ALS patients showed reduced fractional anisotropy values along the mesencephalic CST, suggesting disintegration of fiber tracts. A trend for R-2* values to be elevated was found in the CST of ALS patients. Regarding other brain areas examined, increased R-2* values in ALS patients were observed solely in the caudate nucleus. Conclusion: This study extends previous findings on fiber disorganization by additional quantitative evidence for increased iron deposition in closely localized regions along the CST in ALS patients. Longitudinal studies are needed to further explore the pathophysiologic and diagnostic implications of these findings.