Involvement of pontine transverse and longitudinal fibers in multiple system atrophy: A tractography-based study

Abstract

ObjectivePathological studies showed both pontine transverse (cortico-ponto-cerebellar) and longitudinal (corticospinal) fibers degenerate in MSA. The objective was to investigate the association between the development of cross sign, degenerations of pontine fibers, and the frequency of pyramidal signs in MSA. MethodsPatients with MSA (n=26) and healthy subjects (n=27) were enrolled in this study. Whole pontine transverse and longitudinal fibers were individually traced by diffusion tensor tractography. FA was calculated along each entire tractography. Cross sign was graded as: 0, no cross sign; 1, anterior–posterior line only; and 2, complete cross sign. T2-hyperintense MCPs was graded as: 0, no change; 1, slight signal change; and 2, severe signal change. FA of pontine fibers in MSA patients and that in healthy subjects was statistically evaluated by ANOVA with an overall statistical significance level of 0.05. The frequency of pyramidal signs in MSA was compared between each cross and MCP grade. ResultsFA of pontine transverse fibers in MSA patients decreased with the development of cross sign. FA of Cross 2 was significantly lower than that of healthy subjects (p=0.003). As regards pontine longitudinal fibers, FA decreased when cross sign was completed. The frequency of pyramidal signs in MCP 2 and 1 was higher than that in MCP 0. ConclusionPontine transverse fibers degenerate as cross sign develop, and degenerations of pontine longitudinal fibers begin, or even accelerate when cross sign becomes apparent. Pyramidal signs are frequently present when T2-hyperintense MCPs are clearly observed.