Proton magnetic resonance spectroscopy of the motor cortex in 70 patients with amyotrophic lateral sclerosis

Objective: To evaluate proton magnetic resonance spectroscopy for detection and monitoring of upper motoneuron degeneration in patients with amyotroph ic lateral sclerosis. Methods: Seventy patients with amyotrophic lateral sclerosis according to t he El Escorial criteria were compared with 48 healthy control subjects. Sin gle-volume proton magnetic resonance spectroscopy (echo time, 272 milliseco nds; repetition time, 2000 milliseconds) was performed in both motor cortic es for detection of N-acetylaspartate (NAA), phosphocreatine+creatine ([PIC r), and choline-containing compounds (Cho) to calculate the metabolite rati os NAA/Cho, NAA/(P)Cr, and Cho/ (P)Cr. In addition, absolute metabolite con centrations of NAA, (P) Cr, and Cho were obtained in 30 patients and 15 con trols with the unsuppressed water signal used as an internal reference. Results: Absolute concentrations of NAA (P<.001) and (P)Cr (P<.05) were red uced in motor cortices of patients, whereas Cho concentrations remained unc hanged. The NAA/Cho and NAA/(P)Cr ratios were reduced in all El Escorial su bgroups (P<.001). The Cho/(P)Cr ratio was elevated in patients with definit e amyotrophic lateral sclerosis (P<.05). Metabolite ratio changes correspon ded to the lateralization of clinical symptoms and were weakly correlated w ith disease duration and disease severity. In follow-up observations of 16 patients during a mean (+/-SD) of 12.1+/-8.7 months, NAA/Cho dropped by 9.1 % (P<.01), and Cho/(P)Cr increased by 7.0% (P<.01). Changes of metabolite r atios were significantly correlated with progression of disease severity. Conclusions: Measurement of NAA concentrations and NAA/Cho ratios appear to be most suitable for detection of motor cortex degeneration by single-volu me proton magnetic resonance spectroscopy. Reduced NAA/Cho ratios correspon d to aspects of the clinical presentation and reflect disease progression i n follow-up measurements.