PROTON MAGNETIC-RESONANCE SPECTROSCOPIC IMAGING OF CORTICAL GRAY AND WHITE-MATTER IN SCHIZOPHRENIA

Objective: To apply in vivo proton magnetic resonance spectroscopy ima ging estimates of N-acetylaspartate (NAA), a neuronal marker, to clari fy the relative contribution of neuronal and glial changes to the wide spread volume deficit of cortical gray matter seen in patients with sc hizophrenia with magnetic resonance images. Methods: Ten male veterans meeting criteria of the DSM-IV, for schizophrenia and 9 healthy age-m atched men for comparison were scanned using spectroscopic, anatomical , and field-map sequences. Instrument and collection variables were st andardized to allow an estimation of comparable values for NAA, cholin e, and creatine for all subjects. Metabolite values from each voxel on 3 upper cortical slices were regressed against the gray tissue propor tion of that voxel to derive estimates of gray and white matter NAA, c reatine, and choline concentrations. Results: The volume of cortical g ray matter was reduced in patients with schizophrenia, but NAA signal intensity from a comparable region was normal. In contrast, the volume of cortical white matter was normal in patients with schizophrenia, b ut NAA signal intensity from a comparable region was reduced. Conclusi ons: The lack of reduction in gray matter NAA signal intensity suggest s that the cortical gray matter deficit in these patients involved bot h neuronal and glial compartments rather than a neurodegenerative proc ess in which there is a decrease in the neuronal relative to the glial compartment. Reduced white matter NAA signal intensity without a whit e matter volume deficit may reflect abnormal axonal connections.