MR Spectroscopy Findings in Early Stages of Motor Neuron Disease

BACKGROUND AND PURPOSE: Upper motor neuron degeneration varies in different phenotypes of MND. We used single-voxel MR spectroscopy of the primary motor cortex to detect corticomotoneuron degeneration and glial hyperactivity in different phenotypes of MND with a relatively short disease duration, contributing to further delineation of the phenotypes. MATERIALS AND METHODS: We prospectively included patients with ALS-B, ALS-L, and PMA and compared their data with those of patients with PLS and healthy controls. Each cohort consisted of 12 individuals. Disease duration was RESULTS: At baseline, we found significantly decreased NAAx levels and increased mIns levels in PLS. Levels of NAAx and mIns in patients with ALS-L and ALS-B were not significantly different from those in controls, but NAAx levels were significantly lower compared with those in PMA. At follow-up, only in PMA was a decrease of NAAx demonstrated. Glx levels varied widely in all groups. Levels of NAAx and mIns correlated well with clinical variables. CONCLUSIONS: Metabolite changes suggest neuronal dysfunction and active glial involvement in PLS. The corticomotoneuron is affected in early ALS-B and ALS-L, but at a later stage also in PMA. MR spectroscopy data are useful to obtain insight into the disease process at the level of the upper motor neuron in various phenotypes of MND.