MR Spectroscopy May Predict Disability In MS

Llufriu et al, in their article at JAMA Neurology report findings and promise of MR spectroscopy in the evaluation of clinical disability of patients with multiple sclerosis (MS). 

Their study involved 59 patients and 43 healthy controls that were included in a discovery sample and 220 patients in a confirmatory cohort.

Baseline N-acetylaspartate (NAA), myo-inositol (mI) levels in normal-appearing white and gray matter, myelin water fraction in normal-appearing white matter, markers of axonal damage, astrogliosis, and demyelination were evaluated as predictors in a preliminary data set. The potential predictors were subsequently tested for replication in a confirmatory data set. Clinical scores and percentage of brain-volume change were obtained annually over 4 years as outcomes.

NAA and mI had statistically significant effects on brain volume, prompting the use of the mI:NAA ratio in normal-appearing white matter as a predictor.   Furthermore, the mI:NAA ratio predicted clinical disability (Multiple Sclerosis Functional Composite evolution: −0.52 points annually, P < .001; Multiple Sclerosis Functional Composite sustained progression: odds ratio, 2.76/SD increase in the ratio; 95% CI, 1.32 to 6.47; P = .01) in the preliminary data set and predicted Multiple Sclerosis Functional Composite evolution (−0.23 points annually; P = .01), Expanded Disability Status Scale evolution (0.57 points annually; P = .04), and Expanded Disability Status Scale sustained progression (odds ratio, 1.46; 95% CI, 1.10 to 1.94; P = .009) in the confirmatory data set. A new MRI technique allows the estimation of myelin water content derived from the quantification of short T2 relaxometry component. The measure is specific to myelin content and/or its integrity. The myelin water fraction is commonly reduced in normal-appearing white matter, which may reflect active or chronic demyelination.  Myelin water fraction did not show predictive value.

The authors concluded that the mI:NAA ratio in normal-appearing white matter was consistent predictive regarding brain atrophy and neurological disability evolution. The combined presence of astrogliosis and axonal damage in white matter had cardinal importance in disease severity.

Combined MRS and DWI could Predict Stroke's Outcome

Parsons etal in their article that appeared in Neurology¹ report on the prognostic value of the biochemical changes seen with proton MR spectroscopy (MRS) in patients with ischemic stroke.

Nineteen patients had 36 1H MRS studies, 13 of the patients acutely (mean, 11.1 hours), 10 patients sub-acutely (mean, 3.9 days), and 13 patients at outcome (mean, 82 days). Single-voxel, long-echo, timepoint-resolved spectroscopy was used to obtain lactate, n-acetylaspartate (NAA), choline, and creatine levels from the infarct core. Diffusion-weighted imaging (DWI) was used to identify regions of ischemia for 1H MRS voxel localization.  Outcome measures were final infarct volume and clinical assessment scales (Canadian Neurological Scale, Barthel Index, and Rankin Scale).

Acute lactate/choline ratio correlated more strongly with clinical outcome scores and final infarct size than acute DWI lesion volume or acute NAA/choline ratio. Combination of acute lactate/choline ratio and DWI lesion volume improved prediction of all outcome scores. The predictive effect of acute lactate/choline ratio was independent of acute DWI lesion volume (p < 0.001). In subacute and chronic infarction, both lactate/choline and NAA/choline ratios continued to correlate with outcome (p < 0.05). At the chronic stage, persistent lactate/choline ratio elevation strongly correlated with outcome measures (r = 0.71 to 0.87).

The authors concluded that lactate/choline ratio measured in the acute infarct core by 1H MRS improves the prediction of stroke outcome and provides prognostic information complementary to DWI.

1. Parsons M, Barber P, Yang G, Darby et al: Combined (1)H MR spectroscopy and diffusion-weighted MRI improves the prediction of stroke outcome. Neurology. 2000 Aug 22;55 (4):498-505