A proton magnetic resonance spectroscopic study in ALS: correlation with clinical findings

To evaluate neuronal dysfunction in the motor region subcortical white matter in ALS using volumetric localized proton magnetic resonance spectroscopy (1H-MRS).

Sixteen patients with E1 Escorial definite, probable, or possible ALS and eight healthy age-matched control subjects were studied. The ALS patients were divided into those with limb onset (n = 8) and those with bulbar onset (n = 8). Measurements of the metabolic ratios N-acetylaspartate (NAA)/creatine and phosphocreatine (Cr+PCr), NAA/choline (Cho), and Cho/(Cr+PCr) were correlated with clinical assessments.

We found no differences in the metabolic peak area ratios in the motor region when comparing the total ALS group and the control subjects. However, correlations were found between the NAA/(Cr+PCr) ratio and the E1 Escorial category (p = 0.03), the ALS severity scale (p = 0.01), and the Medical Research Council score (p = 0.06). No correlations were found between the NAA/(Cr+PCr) ratio and the Ashworth Spasticity Scale, reflex score, or disease duration (p > 0.16). Bulbar-onset patients had a lower NAA/(Cr+PCr) ratio in the motor region compared with limb-onset patients (p = 0.03).

In vivo 1H-MRS of the subcortical white matter in the motor region is unlikely to be sensitive enough to detect early disease changes in ALS because there is considerable overlap between the metabolic peak area ratios from patients with ALS and normal control subjects. However, changes in the NAA/(Cr+PCr) metabolic peak area ratios correlate with clinical measures of disease severity, and this measure may be useful in monitoring disease progression.