Restricted diffusion in Wallerian degeneration of the middle cerebellar peduncles following pontine infarction

BACKGROUND: Acute Wallerian degeneration following infarction has been show to result in areas of restricted diffusion within the brain. Very few reports describe this appearance in middle cerebellar peduncles. CASE REPORT: A 37 year old woman was admitted to hospital following sudden collapse and was subsequently found to have a pontine infarct. The complex clinical course resulted in MR imaging including DWI at day 4, 9 and 23 after the initial presentation. The cerebellar peduncles were normal when imaged on day 4 and 9. At day 23, symmetrical high T2 signal was seen in both cerebellar peduncles. The DWI illustrated high signal with corresponding low signal on the ADC map consistent with restricted diffusion. We discuss why this appearance is in keeping with Wallerian degeneration and also describe the fibre pathways involved. CONCLUSIONS: Symmetrical high signal with restricted diffusion in the middle cerebellar peduncles following a pontine lesion is almost certainly attributable to Wallerian degeneration and should not be mistaken for a new ischaemia.