Magnetization transfer measurements of brain structures in patients with multiple system atrophy.

To determine whether magnetization transfer imaging (MTI) demonstrates abnormalities in the brain structures of patients with multiple system atrophy (MSA), we examined 12 patients with clinically probable MSA and 11 control subjects. We calculated magnetization transfer ratios (MTRs) using region of interest analysis from MTI and assessed abnormal signal changes on T2-weighted images. MTRs of the base of the pons, middle cerebellar peduncle, putamen, and white matter of the precentral gyrus were significantly lower in the MSA patients than in the controls. Abnormal signal changes on T2-weighted images were observed in the base of the pons (n = 6), middle cerebellar peduncle (n = 7), and putamen (n = 7). MTRs of regions with abnormal signals were significantly lower than those of regions without abnormal signals and those in the controls. Even the MTRs of the regions without abnormal signals were lower than those in the controls. MTRs of the pyramidal tract, including white matter of the precentral gyrus, posterior limb of the internal capsule, cerebral peduncle, and base of the pons, were significantly lower in patients with pyramidal tract sign (n = 7) than in the controls. Patients with asymmetrical parkinsonism (n = 5) showed significantly lower MTRs in the putamen contralateral to the predominant side of parkinsonian symptoms than the ipsilateral side, although asymmetry of abnormal signal changes on T2-weighted images was not evident in more than half of those patients. This study showed that MTI demonstrates abnormalities in the brains of patients with MSA that seem to reflect underlying pathological changes and that the pathological changes detected by MTI seem to give rise to clinical symptoms. This study also showed that the abnormalities are detected more sensitively and over a larger area by MTI than by conventional magnetic resonance imaging.