Magnetization transfer imaging and magnetic resonance spectroscopy of normal-appearing white matter in late-life major depression.

Abstract

To examine the relationships between the damaged macromolecular pool seen on magnetization transfer (MT) imaging and cerebral metabolic changes recorded by magnetic resonance spectroscopy (MRS), in frontal white and gray matter regions of late-life MDD patients. MT imaging and MRS were performed on eight patients with late-life MDD and eight age-matched healthy controls. MT ratios were calculated using the on-resonance and off-resonance images. Correlations were computed between MT ratios and the ratios of several metabolites, including choline (Cho), myo-inositol (mI), N-acetylaspartate (NAA), and N-acetylaspartylglutamate (NAAG), to creatine (Cr). Statistically significant correlations were found in white matter between the MT ratios and mI/Cr (r = -0.90, N = 7, P = 0.016), and between the MT ratios and (NAA + NAAG)/Cr (r = -0.89, N = 8, P = 0.007). No significant correlations were found in gray matter or between the MT ratios and NAA/Cr or Cho/Cr in white matter. Changes in the white matter macromolecular protein pool, observed as reduced MT ratios, may be related to changes in the mI and the total NAA pools. These findings may have implications for the pathophysiology of late-life major depression.