ESTIMATION OF BRAIN-STEM NEURONAL LOSS IN AMYOTROPHIC-LATERAL-SCLEROSIS WITH IN-VIVO PROTON MAGNETIC-RESONANCE SPECTROSCOPY

In vivo proton magnetic resonance spectroscopy (MRS) may be used to qu antify brainstem neuronal degeneration in ALS because of the neuronal localization of N-acetylaspartate and N-acetylaspartylglutamate, toget her termed NA, which are estimated with this technique. We measured th e ratio of NA to creatine/phosphocreatine (NA/Cr) with proton MRS at 3 .0 tesla (T) in a 4.3-cm(3) volume in the pens and upper medulla of 12 ALS patients and 17 age-matched control subjects. Brainstem NA/Cr was reduced in ALS versus control subjects (mean +/- SD: 1.57 +/- 0.20 ve rsus 1.95 +/- 0.14; p < 0.0001). Patients with severe spasticity or pr ominent bulbar weakness had the lowest NA/Cr ratios; those with predom inantly lower motor neuron limb weakness had near-normal ratios, We co nclude that proton MRS may quantify region-specific neuronal dysfuncti on in ALS.