[MR images of wallerian degeneration--relation between the time and MR findings of wallerian degeneration].

On magnetic resonance (MR) images, wallerian degeneration of the pyramidal tract can be demonstrated as an abnormal intensity showing prolonged T1 and T2 relaxation times corresponding to the corticospinal tract, and/or as shrinkage of the ipsilateral cerebral peduncle and pons. We evaluated 150 cases with supratentorial cerebrovascular accident (CVA) and found the above findings in 35 patients (hematoma 21, infarction 14). The time interval between the ictus of CVA and manifestation of wallerian degeneration on MR images was evaluated. In all 35 cases the foci of CVA located at or extended into the motor cortex, the corona radiata of the pyramidal tract or the posterior limb of the internal capsule. Abnormal signal intensity appeared as early as 5 weeks after ictus and was observed in all 17 cases after 10 weeks. Ipsilateral shrinkage of the cerebral peduncle and the pons has appeared 13 months after ictus. MR appears to be the most useful modality for early detection of waller degeneration.