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Wallerian degeneration of the corticospinal tract in the brain stem: MR imaging.

Magnetic resonance imaging (MRI) of wallerian degeneration of the corticospinal tract in the brain stem was studied in 25 patients with chronic supratentorial vascular accidents. In the relatively early stages, at least three months after ictus, increased signal intensities in axial T2-weighted images--with or without decreased signal intensities in axial T1-weighted images--were observed in the brain stem ipsilaterally. In later stages, at least six months after ictus, shrinkage of the brain stem ipsilaterally--with or without decreased signal intensities--was clearly observed in axial T1-weighted images. MRI is therefore regarded a sensitive diagnostic modality for evaluating wallerian degeneration in the brain stem.