[A case showing Wallerian degeneration of the bilateral middle cerebellar peduncles on MRI followed by the right pontine infarction].

We report a 63-year-old man who presented with the left facial palsy, the left hemiparesis, the left limb ataxia, and the bilateral truncal ataxia. On admission, magnetic resonance imaging (MRI) showed an abnormal high intensity lesion at the right paramedian region of the upper to middle pons on T2-weighted images (T2WI). He was diagnosed as having a pontine lacunar infarction. The contralateral cerebellar lesions were caused by involvement of the pontocerebellar fibers. On the 29th day from the onset, MRI showed the new abnormal high intensity lesions at the bilateral middle cerebellar peduncles on T2WI. These lesions were supposed to be Wallerian degeneration caused by involvement of the pontocerebellar fibers. This case suggests that Wallerian degeneration occurs followed by a unilateral infarction involving pontocerebellar fibers.