Longitudinal MRI study of multiple system atrophy – when do the findings appear, and what is the course?
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Several investigators have revealed features of multiple system atrophy (MSA) by magnetic resonance imaging (MRI). For use in clinical diagnosis, we determined the exact time when two main features of pontine and putaminal intensity changes appeared. Furthermore, in order to reveal the course from when the disorder first appeared and how it spread, we also investigated the course of MRI findings and differences between clinical subtypes. The cranial MRI of 42 patients with MSA were longitudinally studied including comments on the so called “cross sign” of pontine T2 high intensity, which was divided into 6 stages, and also on the linear T2 high intensity of the dorsolateral side of the putamen (“putaminal slit”) which was divided into 4 stages. Patients were classified as 16 MSA-C, 7 autonomic dominant type (MSA-A), and 19 MSA-P. The age at onset ranged from 41 to 74 years (mean, 55 ± 9). The duration of the disease in the MRI study ranged from 1 to 24 years. The pontine “cross sign” was completed (shows Cross, stage IV) earlier in MSA-C mainly before 5 years, later in MSA-P and even much later in MSA-A. Regarding the “putaminal slit”, MSA-P shows earlier bilateral changes (stage II), mostly before 3 years, compared with MSA-C, which requires 4 years to reveal even a unilateral change (stage I), or MSA-A which requires even more time. MRI findings showed a tendency to relate to clinical findings, since MSA-C exhibits “cross sign” completion earlier than bilateral “putaminal slit”; however, MSA-P shows bilateral “putaminal slit” earlier than “cross sign”, and MSA-A requires much more time to show both. Clinically, MSA-C, MSA-A, or MSA-P showed different MRI courses so that three subtypes could be defined also with MRI findings. Therefore these observations are useful not only for diagnosis of MSA itself, but also to distinguish clinical subtypes (MSA-C, MSA-A, or MSA-P) which have different rates of lesion progression.
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