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. 2006 Jun-Jul;27(6):1234-8.

Diffusion tensor imaging in amyotrophic lateral sclerosis: volumetric analysis of the corticospinal tract

S Wang  1 , H Poptani, M Bilello, X Wu, J H Woo, L B Elman, L F McCluskey, J Krejza, E R Melhem
Affiliations

Diffusion tensor imaging in amyotrophic lateral sclerosis: volumetric analysis of the corticospinal tract

S Wang et al. AJNR Am J Neuroradiol. 2006 Jun-Jul.

Abstract

Background and purpose: Diffusion tensor imaging (DTI) allows direct visualization and volumetric analysis of the corticospinal tract (CST). The purpose of this study was to determine whether color maps and fiber tracking derived from DTI data are valuable in detecting and quantifying CST degeneration in patients with amyotrophic lateral sclerosis (ALS).

Methods: Sixteen patients with ALS with clinical signs of upper motor neuron (UMN) involvement and 17 healthy subjects were studied with the use of DTI. Disease severity was determined by means of the ALS Functional Rating Scale-Revised (ALSFRS-R) and an UMN involvement score. DTI was acquired with a 12-direction, single-shot, spin-echo echo-planar sequence. The CST from the lower pons to the corona radiata at the level of the corpus callosum on 4 contiguous coronal sections was manually segmented by using color maps generated from the DTI data. The left and right CST volumes were measured separately and normalized to the total intracranial volume. Normalized CST volumes were compared between patients with ALS and healthy subjects.

Results: The CST volumes of patients with ALS were significantly reduced (P < .01, unpaired t test) compared with healthy subjects, in both affected and nonaffected hemispheres. No significant correlation was found between CST volumes and any of the clinical parameters, including disease duration, ALSFRS-R, or UMN involvement score.

Conclusion: This study shows that volumetric analysis by using DTI-based color maps is valuable in detecting and monitoring structural degeneration of the CST. This will lead to objective and quantitative assessment of axonal degeneration in ALS.

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Figures

Fig 1.
Fig 1.
Diffusion tensor imaging-based color map of a healthy subject. Colors indicate directions as follows: red, left-right; green, anteroposterior; blue, superior-inferior. The white line delineates manually segmented corticospinal tract (CST) (A). Reconstructed CSTs (green) are overlaid on color maps (B).
Fig 2.
Fig 2.
Diffusion tensor imaging-based color maps of a healthy subject (A) and a patient with amyotrophic lateral sclerosis (ALS) (B). The left corticospinal tract (arrows) appears thinner in the patient with ALS (B).
Fig 3.
Fig 3.
Region of interest (ROI) placement on the reconstruction of corticospinal tract (CST) at the level of precentral gyrus (A, white) and lower pons (B, orange). Fiber tracking images of a healthy subject (C) and a patient with amyotrophic lateral sclerosis (ALS) (D). The rectangle in C indicates section location of ROIs. Descending fibers connecting the cortex and brain stem are shown in purple. CSTs are green. The CST fibers are diminished in the patient with ALS (D).
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