Combined MR spectroscopic imaging and diffusion tensor MRI visualizes corticospinal tract degeneration in amyotrophic lateral sclerosis

Abstract

Motor neuron damage and cortical spinal tract (CST) degeneration are pathological features of amyotrophic lateral sclerosis (ALS). We combined whole-brain diffusion tensor imaging (DTI) and three-dimensional magnetic resonance spectroscopic imaging (MRSI) to study the CST at different locations. Eight ALS patients were compared with normal controls. Fractional anisotropy (FA) and mean diffusivity (MD), and the ratio of N-acetyl-aspartate (NAA) to creatine (Cr) were measured at various locations in the CST, including the subcortical white matter (SWM), centrum semiovale (CS), periventricular white matter (PV), posterior limb of the internal capsule (PIC) and cerebral peduncle (CP). Patients showed significantly lower FA than controls in the CST, including the SWM, CS, PV and PIC. Although there was a trend towards elevated MD in ALS patients, this did not reach statistical significance. NAA/Cr ratios were also decreased in ALS patients compared with normal controls, with significant differences in the SWM and PV but not in PIC. Combined whole-brain DTI and MRSI can detect axonal degeneration in ALS. Measurements of FA obtained in the SWM, CS, PV and PIC, and NAA/Cr ratios in the SWM and PV yield the most robust results.

Combined 3T Diffusion Tensor Tractography and1H-MR Spectroscopy in Motor Neuron Disease

“…We thus provide data for a patient subgroup with clinical lower motor neuron disease only, which is considered a target group for future ALS studies. 21,45 Because studies using high-field magnets (Ն3T) and applying both spectroscopy and DTI to the same patients with suspected ALS are still rare, 22,23 reviews regarding congruent or incongruent results of both techniques are essential. In the present study, MR spectroscopy and DTI agreement was high: Markedly reduced FA with corresponding NAA reductions occurred in all clinically definite/probable patients with ALS, with a total of only 3 divergent findings.…”

“…MD differences tend to be lost caudally in the CST 48 and, furthermore, could not be ascertained by other groups. 22 For the motor region and centrum semiovale, it is questionable whether MD changes correlate with disease processes or are not rather due to extracellular volume increases in the course of atrophic changes.…”

“…21,22 However, systematic evaluation of their concordance in the same patients is still rare. 21,23 To obtain a definite diagnosis early in the disease is important for therapeutic intervention, 21,24 quality of life, 17,25,26 and monitoring therapeutic trials.…”

“…21,23 To obtain a definite diagnosis early in the disease is important for therapeutic intervention, 21,24 quality of life, 17,25,26 and monitoring therapeutic trials. 16,22 Cervical myelopathy, Kennedy syndrome (spinobulbar muscle atrophy, [SBMA]), peripheral nerve lesions, and multifocal polyneuropathy are, among others, differential diagnoses that have to be excluded. The clinical diagnosis is especially difficult when UMN involvement remains unclear.…”

Neuroimaging in Amyotrophic Lateral Sclerosis

“…In the search for the UMN markers, several neuroimaging modalities, especially diffusion tensor imaging (DTI) [8][9][10][11][12][13][14][15][16], proton magnetic resonance spectroscopy ( 1 H-MRS) [14,15,[17][18][19][20], perfusion imaging [21], magnetization transfer imaging [22] (MTI) and functional magnetic resonance imaging (fMRI) [23][24][25], have been used with varying success. This article presents an overview of these neuroimaging methods and their potential roles in ALS.…”