Detection of cerebral degeneration in amyotrophic lateral sclerosis using high-field magnetic resonance spectroscopy

Background: Clinical assessment is insensitive to the degree of cerebral involvement in amyotrophic lateral sclerosis (ALS). Regional brain concentrations N-acetylaspartylglutamate (NAA) plus myo-inositol (Ins), as measured by magnetic resonance spectroscopy, are respectively decreased and increased, suggesting that these compounds may provide a biomarker of the degree of cerebral involvement in ALS. Objective: To test the hypothesis that the NAA/Ins ratio may provide an index of cerebral involvement in patients with ALS. Design: High-field (3.0-T) magnetic resonance spectroscopy was performed to determine the NAA/creatine plus phosphocreatine (NAA/Cr), NAA/choline (NAA/Cho), Ins/Cr, and NAA/Ins ratios in the motor cortex. Participants: Seventeen patients with ALS and 15 healthy control subjects were studied. Results: In patients with ALS, the greatest abnormality was a 22% decrease in NAA/Ins (71% sensitivity and 93% specificity, P=.001); Ins/Cr was increased 18% (88% sensitivity and 53% specificity, P=.04), NAA/Cr was decreased 10% (88% sensitivity and 47% specificity, P=.04), and NAA/Cho was decreased 14% (53% sensitivity and 87% specificity, P=.047). Correlation of the ALS Functional Rating Scale with NAA/Ins approached statistical significance (R=0.43, P=.07). Conclusion: The NAA/Ins ratio may provide a meaningful biomarker in ALS given its optimal sensitivity and specificity profile.