Evaluation of corticospinal tracts in ALS with diffusion tensor MRI and brainstem stimulation

Abstract

Fractional anisotropy reflects functional abnormality of intracranial corticospinal tracts and can be used for objective evaluation of upper motor neuron impairment in amyotrophic lateral sclerosis.

Assessment of White Matter Tract Damage in Patients with Amyotrophic Lateral Sclerosis: A Diffusion Tensor MR Imaging Tractography Study: Fig 1.

“…The finding of increased MD and radial D and reduced FA in the CST of patients with ALS is in agreement with previous studies, [8][9][10][11][12][13][14][15]23 confirming that DTI is a valuable tool for assessing CST changes in ALS. An increased average MD can result from the enlargement of extracellular spaces, which indicates a breakdown of the barriers that restrict free water movement.…”

“…5,6 Most DTI studies in ALS have been limited to the assessment of the CST damage. 7 Whether on the basis of regions of interest, [8][9][10][11][12][13][14][15][16] voxel-based analysis, [17][18][19][20] or tractography, [21][22][23] DTI studies in ALS have shown reduced FA along the CST.…”

Widespread Microstructural White Matter Involvement in Amyotrophic Lateral Sclerosis: A Whole-Brain DTI Study

“…These results are consistent with previous DTI correlation analyses between FA and clinical measure of disease severity and progression within the pyramidal system. 2,10,16,46 However, not all previous MR imaging studies reported significant correlations between diffusivity parameters and clinical scores in ALS, 4,7,11,15 probably due to the following: 1) the intrinsic heterogeneity of the pathologic process (in ALS, degeneration of fiber tracts may not be a classic wallerian degeneration in terms of the contribution from intra-and extracellular changes, astrocytosis, disorders of axonal transport, and accumulation of axonal spheroids 29 ); 2) the different clinical characteristics of the patients, with predominantly upper or lower motor neuron signs and different disease duration and disability; 3) the lack of clinical scores highly specific for the detection of UMN impairment (associations between clinical symptoms and pathologic findings are weak because it has been shown that prominent clinical disability may occur even in the absence of impairment of the CSTs, and vice versa) 29 ; and 4) the different methodologies used.…”

“…2 DTI is a relatively new method for structural neuroimaging, which allows visualizing the orientation of the fiber tracts and assessing their integrity in the WM by measuring anisotropic water diffusion properties of the brain with MR imaging. 3 DTI has already produced promising results in assessing UMN pathology in patients with ALS, 2,[4][5][6][7][8][9] suggesting that FA, the most sensitive DTI measure, is reduced along the CSTs due to axonal degeneration and loss of fiber integrity, 2,4-6 though AD, MD, and RD changes along the CSTs and other WM structures may also be indicative of degenerative injury. 8,9 Significant correlations of diffusion parameters with duration, progression, and severity of the disease also have been reported in some previous studies.…”

A Distinct MR Imaging Phenotype in Amyotrophic Lateral Sclerosis: Correlation between T1 Magnetization Transfer Contrast Hyperintensity along the Corticospinal Tract and Diffusion Tensor Imaging Analysis

“…[26][27][28][29][30][31][32][33][34][35][36][37][38][39] Reduced FA along the CST from the corona radiata through the internal capsule and into the brain stem has been reported by using both regionof-interest 27,32,36 and voxel-based approaches. 28,33,35,38,40 In addition, some authors 28,35 described a decrease in FA, not only in the CST but also in regions outside the main motor cortices and the CST.…”